Tonghui TH2821A LCR Meter

[Mike]

Here's something that may interest some folks here. I just got my new
Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed.

After some screwups due to a discharged internal battery and not reading
the instructions, it is starting to give some really impressive results.

5 digits resolution on 1000uf caps, 4 digits on iron-core inductor,
miscellaneous resolution on 30k resistors (I haven't figured out how to
measure resistance yet, but it should be very easy:)

Here's the eBay info:

LCR RCL LC Meter TH2821A inductance Capacitance 10kHz

Price : US $164.93
Shipping : $25.00
Item : 320492041898

It can measure 6 basic parameters: inductance L, capacitance C,
resistance R, impedance Z, dissipation factor D and quality factor
Q.

It has measurement accuracy of 0.3% and 4-bin sorting.

Applied complete 5-terminal measurement configuration solves problem
of measurement for equivalent series resistance and capacitor with
small dissipation that other portable LCR meters can't solve. It can
replace general low-frequency LCR meter.

Only portable LCR meter at home
Large LCD display
Measurement frequency up to 10kHz
Basic accuracy: 0.3% with resolution of 0.01%
5-side measurement technology to provide accurate measurement of ESR
and loss
Sweep Clear Function
battery and external power supply power supply
fourth gear sorting

Measurement Signal

Signal Frequency : 100Hz 120Hz 1KHz,10KHz
OutPut Impedance : Dependent on range
Test level : 0.3Vrms

Measurement display range

R : 0.0001Ohm ~ 99.999Ohm
C : 0.01pF ~ 9999uF
L : 0.01uH ~ 9999H
D,Q : 0.0001 ~ 9.9999
?% : -999.99% ~ 999.99%

Comparator

Comparator : 4bins: NG, P1, P2, P3 with beeper alarm

You can also get smd tongs:

LCR METER-SMD/CLIP,TWEEZERS,TH26029 FOR TONGHUI,
US $36.00

Item : 350502463639

The manual is dated November 2005, 1st Edition Rev 1.0.0

"http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation%
20Manual.pdf"

Specifications

"http://www.ekt2.com/_files/40%20TONGHUI%20TH2821.pdf"

Datasheet

"http://www.aet.com.pl/Portals/0/katalogi_pdf/maszyny_zalewy_impregnaty/m
ostki_rlc/th2821.pdf"

You can also get the TH2821B, which goes to 1KHz

Item: 350501591362

Price: US $136.00

The only problem so far is they shipped a 220VAC adapter, which does not
work on 120VAC. After some discussions, they shipped a universal 100-
240VAC adapter which should work anywhere. If you want one, be sure and
tell them to ship the universal 100-240VAC adapter. But they are very
nice to deal with and you should have no problems.

For the performance and price, I don't think you can beat this anywhere.
I especially like being able to measure ESR of large electrolytics, since
I have a lot of eBay boat anchors that need some care.

So far the performance is excellent. I'll post if I come across any
surprises.

Regards,

Mike

[D from BC]

I bought something like this. There are variations.

Ebay
220766760779

$40.00 with shipping.

High Precision L/C Inductance Capacitance Digital Meter

Specification:

Measurement accuracy: 1%
Capacitance Measuring range: 0.01pF~10uF
Minimum resolution: 0.01pF
Inductance Measuring Range: 0.001uH ~ 100mH
Large Inductance Measuring Range: 0.001mH ~ 100H
Minimum resolution: 0.001uH
Test Frequency: about 500Hz
LCD effective display digits: 4
Display Method: 1602 LCD
Power Supply: Mini USB interface, 5V interface
Size: 81 x 47 x 30 mm ( L*W*H )

I power it up using my scope USB port.

Most of my apps don't require accuracy.
For say around 50nH then I set up a generator and a scope.

Cheap! Cheap! Cheap!

[Mike]

Mike <sp...@me.not> wrote:

> 5 digits resolution on 1000uf caps, 4 digits on iron-core inductor,
> miscellaneous resolution on 30k resistors (I haven't figured out how
> to measure resistance yet, but it should be very easy:)

The resistance measurements are now OK once the internal battery is
charged. This issue is mentioned in the manual. The unit comes with the
battery discharged, so you just have to wait until it is charged before
starting to play with it.

It gives 4 digits of resolution on a 30k resistor. This is adequate for
most ordinary needs.

Altogether, I'm very pleased. It has already identified a bad electrolytic
in a circuit where there are several that could be causing the problem. The
rest are fine.

Mike

[Mike]

Mike <sp...@me.not> wrote:

The TH2821A appears to be discontinued, but there may still be some stock
left on eBay.

The replacement is the TH2822C, which goes up to 100KHz and offers
averaging, 40,000 counts, 16 hours operation on internal battery, TH2822C
has optional rechargeable batteries, Standard Mini-USB interface, etc.

Here's the feature list:

* Basic measurement accuracy: 0.25%
* Gorgeous dual-color cast shell
* Maximum test signal frequency: 100kHz (TH2822C)
* 40,000 counts for primary parameter, D/Q resolution 0.0001
* Typical ultra-low consumption : 25mA
* Battery capacity: TH2822/TH2822A continuously used for 16 hours
* TH2822C rechargeable batteries are optional
* Innovatively compatible terminal configuration : 5-terminal test
slot and 3-terminal banana jack
* Intelligent Auto LCR function
* Measurement speed up to 4 meas/sec
* fast automatic range switch design
* Constant output impedance: 100 Ohm
* Percentage display and 4-tolerance comparator: 1%, 5%, 10%,
20% (20% not available for TH2822)
* Automatic OPEN/SHORT correction detection
* Data Hold, Max/Min/ Average recording
* Utility function configuration and current setup recovery after
power-off
* Standard Mini-USB interface, SCPI compatible
* Firmware update through Mini-USB interface
* Free FastAccess communication software on our website

The web page is

http://www.tonghui.com.cn/en/goods/index/250.html

The TH2822C are vailable on eBay for around $474.70

It looks like the TH2821A is a pretty good deal for the price, if you can
still get one:)

Thanks,

Mike

[John S]

You talked me into it, Mike. The specs look super to me and I've been
needing something like it.

Do you get probes with it so you can test components on a populated board?

Thanks for the find.

John S

[Mike]

John S <sop...@invalid.org> wrote:

> You talked me into it, Mike. The specs look super to me and I've
> been needing something like it.

> Do you get probes with it so you can test components on a
> populated board?

> Thanks for the find.

> John S

Which one are you getting - TH2821A or TH2822C?

The SMD probe I mentioned earlier is for the TH2821A. It is
available on eBay:

LCR METER-SMD/CLIP, TWEEZERS, TH26029 FOR TONGHUI,
Price: US $36.00
Item : 350502463639

It won't work on the TH2822, but they should have something that
does work.

For populated boards, of course you have to watch for other
components in parallel. But the measuring voltage seems to be too
low to turn on silicon junctions, so it should work OK in most
situations.

I was afraid of accidentally testing a charged electrolytic, which
is how I destroyed my last capacitance meter. So I tried adding a
fast silicon diode in parallel with a large electrolytic.

As far as I can tell, it has little or no effect on the reading. But
it makes the instrument go nuts when there is no electrolytic
capacitor to measure. I will make a little test fixture that adds
two fast 3A diodes back-to-back in parallel with the test probes to
try to avoid making the same mistake in the future.

I find sometimes the reading on the TH2821A fluctuates a bit. You
have to find the correct test frequency for the component you are
trying to measure.

I would really like the ability to average the readings, which is
provided in the TH2822C. But the price is way more than I am willing
to pay.

Once it gets to that level, I seriously start thinking of making my
own unit. With the components available to us these days, it should
be possible to beat the performance of almost anything on the
market.

For example, there are two vector network analyzers available on the
web that you can build yourself. Both are in the Yahoo forums, and
they seem to be very good instruments. But already there is a much
better version of the DDS than the one they are using. That should
improve the performance substantially.

There is also a spectrum analyzer you can build yourself. But I
happen to have a 8566 so that is not too interesting at the moment.

The only problem is if the 8566 dies and needs some unobtanium part.

That already happened to a HP 8505 network analyzer that I bought
new, and was discontinued the week after I paid cash for it. It ran
for a number of years, then it died. It would have cost too much to
get it repaired, so I just put it in a dumpster and promised myself
I would never buy another expensive instrument. Either get it on
eBay for pennies, or build it myself.

Ultimately I would rather have my own stuff. It will take much less
room on the bench, have usb interface for control, and be much
easier to repair or upgrade as time goes on.

Regards,

Mike

[P E Schoen]

About four years ago I purchased a similar unit, the MCP BR2822 LCR
http://www.mcpsh.com/BR2821%20BR2822.html
I paid $250 for it and except for some problems with the battery, it seemed
OK. But I have not used it much. I think I got it from these guys:
http://www.multimeterwarehouse.com/BR2822.htm,
who now want $349 for it. Amazon has it for $300.
http://www.amazon.com/MCP-BR2822-Professional-10KHz-Digital/product-reviews/B000TYUZM0

I also bought a $50 LCR that I use for everyday purposes:
http://www.amazon.com/Sinometer-MS8222H-Digital-Multimeter-Meter/dp/B000MFIDC0.
It's OK, but sometimes I have to fiddle with the switch and/or the leads to
get continuity.

I'm waiting for delivery on:
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=190450842291&ssPageName=ADME:L:OU:US:1123
and
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=190452347958&ssPageName=ADME:L:OU:US:1123

I'm considering the following unit:
http://www.ebay.com/itm/320780815383?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
or maybe this:
http://www.ebay.com/itm/330633195250?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Paul

[Mike]

"P E Schoen" <pa...@pstech-inc.com> wrote:

> About four years ago I purchased a similar unit, the MCP BR2822 LCR
> http://www.mcpsh.com/BR2821%20BR2822.html
> I paid $250 for it and except for some problems with the battery, it
> seemed OK. But I have not used it much. I think I got it from these
> guys: http://www.multimeterwarehouse.com/BR2822.htm,
> who now want $349 for it. Amazon has it for $300.
> http://www.amazon.com/MCP-BR2822-Professional-10KHz-Digital/product-rev
> iews/B000TYUZM0

That looks identical to the TH2821A!

> I also bought a $50 LCR that I use for everyday purposes:
> http://www.amazon.com/Sinometer-MS8222H-Digital-Multimeter-Meter/dp/B00
> 0MFIDC0. It's OK, but sometimes I have to fiddle with the switch
> and/or the leads to get continuity.

Yes, I have a bunch of dmms. Some measure capacitance, but none measure
ESR. You need that to weed out the bad electrolytics in eBay boat
anchors.

> I'm waiting for delivery on:
> http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=190450842291&ssP
> ageName=ADME:L:OU:US:1123 and
> http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=190452347958&ssP
> ageName=ADME:L:OU:US:1123
>
> I'm considering the following unit:
> http://www.ebay.com/itm/320780815383?ssPageName=STRK:MEWAX:IT&_trksid=p
> 3984.m1423.l2649 or maybe this:
> http://www.ebay.com/itm/330633195250?ssPageName=STRK:MEWAX:IT&_trksid=p
> 3984.m1423.l2649
>
> Paul

For the function generator, I've pretty much decided to go ahead and make
my own using a DDS. You can get microhertz resolution, 0 to 250MHz sine
waves, and USB interface. I think you can get frequency sweep and other
functions, and add your own limiter for square waves. Put two in the same
box for intermodulation testing and mixer development. Add external
filters for high purity sine waves for harmonic distortion. Run it off a
GPS-stabilized reference for the ultimate in frequency stability.

The main thing is you can't predict what you may want to do, so having
the flexibiity to modify your own generator is much better than getting a
commercial unit that may not have the fundamental accuracy and stability
you need. You might be reluctant to modify a commercial unit, or maybe
you don't even get the schematics. But if it's your own, that is no
problem.

Thanks,

Mike

[John S]

On 11/2/2011 10:21 PM, Mike wrote:
> John S<sop...@invalid.org> wrote:
>
> > You talked me into it, Mike. The specs look super to me and I've
> > been needing something like it.
>
> > Do you get probes with it so you can test components on a
> > populated board?
>
> > Thanks for the find.
>
> > John S
>
> Which one are you getting - TH2821A or TH2822C?

TH2821A

> The SMD probe I mentioned earlier is for the TH2821A. It is
> available on eBay:
>
> LCR METER-SMD/CLIP, TWEEZERS, TH26029 FOR TONGHUI,
> Price: US $36.00
> Item : 350502463639

Thanks. I'll look into it.

John S

[John S]

On 11/2/2011 10:21 PM, Mike wrote:

> John S<sop...@invalid.org> wrote:
>
> > You talked me into it, Mike. The specs look super to me and I've
> > been needing something like it.
>
> > Do you get probes with it so you can test components on a
> > populated board?
>
> > Thanks for the find.
>
> > John S
>
> Which one are you getting - TH2821A or TH2822C?
>
> The SMD probe I mentioned earlier is for the TH2821A. It is
> available on eBay:
>
> LCR METER-SMD/CLIP, TWEEZERS, TH26029 FOR TONGHUI,
> Price: US $36.00
> Item : 350502463639
>

BTW, these are also available for those large, TH electrolytics already
on the board:

Item 320702317637

Cheers,
John S

[Mike]

John S <sop...@invalid.org> wrote:

> BTW, these are also available for those large, TH electrolytics already
> on the board:
>
> Item 320702317637
>
> Cheers,
> John S

Good News - those came with the TH2821A.

I have been trying to figure out how they make them into Kelvin contacts.
The contact pads are two sided pcb. I think they may use one side for the
exciting signal and the other side for the sense. It appears they do the
same with the clips, since there are separate leads going to each side.

I put a thin dab of vaseline on the contacts. That provides a bit of
lubrication to minimize wear. It also removes the surface oxides and grime
and allows a true metal-to-metal contact. This reduces the contact
resistance by a factor of ten and stabilizes it. Old radio engineer's trick
from the 1930's

Thanks,

Mike

[Mike]

There are numerous eBay vendors that still offer the TH2821A. The prices
vary quite a bit, but it looks like dealexcel-com has the best offer at the
moment. They want US $185.65, but the shipping is now free. That's where I
got my unit, but the shipping was extra.

If you are interested in getting one, I'd go with them. They already know
about the problem with the 220VAC adapter not working in the US, and they
shipped a replacement that goes from 100VAC to 220VAC so it should work
anywhere.

They send the Kelvin clips with the unit, so you don't have to buy them
separately. They also handle the smd probe, so you can combine the entire
order in one package.

Thanks,

Mike

[ehsjr]

Mike wrote:

<snip>

>
>
> That looks identical to the TH2821A!
>
>
>>I also bought a $50 LCR that I use for everyday purposes:
>>http://www.amazon.com/Sinometer-MS8222H-Digital-Multimeter-Meter/dp/B00
>>0MFIDC0. It's OK, but sometimes I have to fiddle with the switch
>>and/or the leads to get continuity.
>
>
> Yes, I have a bunch of dmms. Some measure capacitance, but none measure
> ESR. You need that to weed out the bad electrolytics in eBay boat
> anchors.
>
>

You can build a go/no go ESR "meter" that'll find the bad 'lytics
for next to nothing. Worth doing, unless you (psychologically)
_must_ have a "real" esr meter.

Ed

[Mike]

> You talked me into it, Mike. The specs look super to me and I've
> been needing something like it.

> Do you get probes with it so you can test components on a
> populated board?

> Thanks for the find.

> John S

Sorry, John. I completely missed your question for some reason. Just
to confirm, the TH26027 Kelvin test cable probe comes with the
TH2821A. It is listed as an accessory on page 4 of the Operator's
Manual:

"http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821A.pdf"

and also listed in the datasheet:

"http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821data%
20sheet.pdf"

I checked the continuity from the two-sided contact pad to the test
clip. The connections are all individual and separate from each
other, so it is a true Kelvin connection all the way to the
component.

Pretty good for a $185US instrument!

Just make sure you get the Universal 100-220VAC adapter.

Thanks,

Mike

[John S]

On 11/3/2011 3:20 PM, Mike wrote:
>> You talked me into it, Mike. The specs look super to me and I've
>> been needing something like it.
>
>> Do you get probes with it so you can test components on a
>> populated board?
>
>> Thanks for the find.
>
>> John S
>
> Sorry, John. I completely missed your question for some reason. Just
> to confirm, the TH26027 Kelvin test cable probe comes with the
> TH2821A. It is listed as an accessory on page 4 of the Operator's
> Manual:

Well, I already bought another set. But, that's okay.

> "http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821A.pdf"
>
> and also listed in the datasheet:
>
> "http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821data%
> 20sheet.pdf"
>
> I checked the continuity from the two-sided contact pad to the test
> clip. The connections are all individual and separate from each
> other, so it is a true Kelvin connection all the way to the
> component.
>
> Pretty good for a $185US instrument!
>
> Just make sure you get the Universal 100-220VAC adapter.
>
> Thanks,
>
> Mike

Maybe I'll send him an email to remind him.

Thanks for the clue.

John S

[Mike]

John S <sop...@invalid.org> wrote:
>
> Well, I already bought another set. But, that's okay.

You talked me into it. I can think of several projects where this would
come in handy. You can never tell when these things will disappear, so I
got a set also.

Thanks for the pointer!

Mike

[D from BC]

I suspect Mike and John are bots.

I will now test.

Hey Mike!
You pathetic blob of useless DNA that didn't get aborted fast enough
with a Black and Decker router.
You're a parasitic garbage making mindless consumer robot that will die
unhappy in your own filth.
You're a fat ugly unwanted unsuccessful unloved uninteresting cockless
guy who lives in a basement with his psychotic crack addicted mother.

[John S]

I had a tiny amount of respect for you until you pulled this crap out of
your ass.

[D from BC]

I do wonder which was more offensive. Being accused of being a bot or my
test insults.

[John S]

I hope you die wondering. Soon.

[Martin Riddle]

"John S" <sop...@invalid.org> wrote in message
news:j94i26$5h9$3...@dont-email.me...

I think it is a Bot, probably Japanese origin from the English and
grammar it uses.

Cheers

[Michael A. Terrell]

It's even worse than that. He's a Canadian troll.


--
You can't have a sense of humor, if you have no sense.

[josephkk]

On Thu, 03 Nov 2011 19:00:10 -0700, D from BC <myreal...@comic.com>
wrote:

D you are a brain dead twit.

?-((

[D from BC]

I use the term 'Bot' cause I'm don't know a word for when someone makes
a fake usenet discussion for the purpose of advertising.
It's a form of spam. Fake discussion spam?
It's a method of dodging user name filtering or I think it's called
ploinking.
Regular spam gets quickly added to filters.
I suspect Mike is John S's puppet.
I could be wrong.

[D from BC]

Not the response I'm expecting.
I'm waiting to be surprised that Mike is real and not an invention of
John S.

[John S]

You are. And, josephkk is right; you are a brain dead twit. And what the
hell business is it of yours?

[D from BC]

I'm just waiting for fake Mike (not user mike) to post an opinion too.

[josephkk]

On Mon, 07 Nov 2011 16:26:23 -0800, D from BC <myreal...@comic.com>

Well here it is. Mike is not a sock puppet of John S. It is obvious to
me as John S in not the kind to ever have or use a sock puppet. Sorry you
could not figure that out.

?-)

[John S]

He is quite stupid. He has not even looked at the message headers. If
that doesn't give him a clue, nothing will.

>:-(

[Michael A. Terrell]

josephkk wrote:
>
> On Mon, 07 Nov 2011 16:26:23 -0800, D from BC ?myreal...@comic.com?
> wrote:
>
> ?On 11/6/2011 2:07 PM, josephkk wrote:
> ?? On Thu, 03 Nov 2011 19:00:10 -0700, D from BC?myreal...@comic.com?
> ?? wrote:
> ??
> ??? I suspect Mike and John are bots.
> ???
> ??? I will now test.
> ???
> ??? Hey Mike!
> ??? You pathetic blob of useless DNA that didn't get aborted fast enough
> ??? with a Black and Decker router.
> ??? You're a parasitic garbage making mindless consumer robot that will die
> ??? unhappy in your own filth.
> ??? You're a fat ugly unwanted unsuccessful unloved uninteresting cockless
> ??? guy who lives in a basement with his psychotic crack addicted mother.
> ??
> ?? D you are a brain dead twit.
> ??
> ?? ?-((
> ?
> ?Not the response I'm expecting.
> ?I'm waiting to be surprised that Mike is real and not an invention of
> ?John S.

>
> Well here it is. Mike is not a sock puppet of John S. It is obvious to
> me as John S in not the kind to ever have or use a sock puppet. Sorry you
> could not figure that out.

He's not even smart enough to know there are a lot of Mikes on this
group. It's no wonder so many have kill filed him after one of his
numerous hissy fits.

[John S]

On 10/31/2011 9:58 PM, Mike wrote:
> Here's something that may interest some folks here. I just got my new
> Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed.

> Regards,
>
> Mike

Hey, Mike -

How long did it take to get your meter?

John S

[Mike]

John S <sop...@invalid.org> wrote:

> Hey, Mike -
>
> How long did it take to get your meter?

> John S

I ordered it on Thu, 8 Sep 2011, it was shipped within a day or so, and it
arrived on Mon, 3 Oct 2011.

That is about normal for shipments from China to Ontario, Canada. You will
probably see faster delivery in the US. I forget which delivery service
they used. Maybe it was DHL.

I really like the dissipation factor on electrolytics. You don't have to
measure the ESR, then go to a lookup table to figure out if that is the
proper value for the capacitance.

I just look at the dissipation factor, and if it's greater than about 0.2
for an older cap, toss it. This is a big time saver.

Mike

[John S]

Great info on delivery AND dissipation. Many thanks.

Cheers,
John S

[Mike]

John S <sop...@invalid.org> wrote:

> Great info on delivery AND dissipation. Many thanks.
>
> Cheers,
> John S

I really think the numbers it gives are quite believable. I just measured
some film capacitors, and the larger ones gave dissipation factors around
0.001 to 0.0005, which corresponds to a Q of 1,000 t0 2,000.

A very small 1.5 nF gave D=0.0002, for a Q of 5,000. That seems a bit high,
but still in the realm of possibility when you consider that is the least
significant digit.

I'm very happy with it so far. Works great, and it autoscales and gives the
reading very fast. This instrument will not slow you down, unless you
forget to discharge a large cap before connecting it to the meter.

Mike

[John S]

On 11/8/2011 4:51 PM, Mike wrote:
> John S<sop...@invalid.org> wrote:
>
>> Great info on delivery AND dissipation. Many thanks.
>>
>> Cheers,
>> John S
>
> I really think the numbers it gives are quite believable. I just measured
> some film capacitors, and the larger ones gave dissipation factors around
> 0.001 to 0.0005, which corresponds to a Q of 1,000 t0 2,000.
>
> A very small 1.5 nF gave D=0.0002, for a Q of 5,000. That seems a bit high,
> but still in the realm of possibility when you consider that is the least
> significant digit.

It depends on the dielectric material. NP0 (C0G) has the lowest D of the
ceramics based on my limited experience. If the one you measured is not
NP0 (C0G) then, yes, the Q reading may be high.

> I'm very happy with it so far. Works great, and it autoscales and gives the
> reading very fast. This instrument will not slow you down, unless you
> forget to discharge a large cap before connecting it to the meter.
>
> Mike

As I said, the specs look great. I'm anxious to get my hands on it. The
instruments I have now put out too much voltage to measure components
in-circuit, so I'm hoping this will help.

Thanks for the additional info.

Cheers,
John

[Mike]

John S <sop...@invalid.org> wrote:

> As I said, the specs look great. I'm anxious to get my hands on it.
> The instruments I have now put out too much voltage to measure
> components in-circuit, so I'm hoping this will help.

> Thanks for the additional info.

> Cheers,
> John

It doesn't seem to mind having a diode across an electrolytic, but I
haven't tried that with lower values like 1 nF.

Let me know what you think of it when you get yours. It would be
interesting to compare notes. But it sure beats the pants off the Capacitor
Wizard, at$229.95:

http://midwestdevices.com/

or $189.95:

http://www.howardelectronics.com/ieinc/cwinfo.html

Mike

[John S]

On 11/8/2011 6:03 PM, Mike wrote:
> John S<sop...@invalid.org> wrote:
>
>> As I said, the specs look great. I'm anxious to get my hands on it.
>> The instruments I have now put out too much voltage to measure
>> components in-circuit, so I'm hoping this will help.
>
>> Thanks for the additional info.
>
>> Cheers,
>> John
>
> It doesn't seem to mind having a diode across an electrolytic, but I
> haven't tried that with lower values like 1 nF.
>
> Let me know what you think of it when you get yours. It would be
> interesting to compare notes. But it sure beats the pants off the Capacitor
> Wizard, at$229.95:

I will.

Errr... The Wizard only tests ESR, yes? I don't think a comparison is
possible under the circumstances.

> http://midwestdevices.com/
>
> or $189.95:
>
> http://www.howardelectronics.com/ieinc/cwinfo.html
>
> Mike

If the TH2821A performs to the specs, then the money is minor and the
Wizard looses miserably.

John S

[k...@att.bizzzzzzzzzzzz]

On Tue, 08 Nov 2011 22:29:40 GMT, Mike <sp...@me.not> wrote:

>
>John S <sop...@invalid.org> wrote:
>
>> Hey, Mike -
>>
>> How long did it take to get your meter?
>
>> John S
>
>I ordered it on Thu, 8 Sep 2011, it was shipped within a day or so, and it
>arrived on Mon, 3 Oct 2011.
>
>That is about normal for shipments from China to Ontario, Canada. You will
>probably see faster delivery in the US. I forget which delivery service
>they used. Maybe it was DHL.

Slow boat. ;-) I had a laptop (Lenovo) shipped from China on a Monday (China
time) and it was delivered on that Wednesday, noonish, to my home in Alabama.
It came UPS.

[P E Schoen]

krw wrote in message news:ciljb7p5u16k66jut...@4ax.com...

> Slow boat. ;-) I had a laptop (Lenovo) shipped from China on a Monday
> (China time) and it was delivered on that Wednesday, noonish, to my
> home in Alabama.
> It came UPS.

Just yesterday I received a DSP shortwave radio I ordered from (I think) the
same supplier.
http://www.ebay.com/itm/190452362072?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
I ordered it 10/25, so that was less than 2 weeks. It came via USPS.
Supposedly air mail.

It's a pretty nice radio, but all the labels and instructions are in
Chinese. I asked for a translation, but I figured out how most of the
functions work. Not bad for $24 total including shipping.

I'm still waiting on some other items. And I found that they play games with
pricing and shipping. For instance, I've seen something for about $20, with
free shipping. And then I found the same item for $0.99, with $19 shipping.

I use www.pcbcart.com for my PC boards, and they usually arrive about a week
after ordering.

Thanks (to Mike, I guess) for the alert to these bargains. I might order
some other things. Their USB 200x microscopes sound interesting.

Paul

[Mike]

I am in Canada, the land of polar bears and dog sleds. It snows here.

I just ordered the top853 USB universal programmer mentioned by Nico
Coesel, http://www.ebay.com/itm/160378432470

I just received the following email from them:

We shipped YOUR item from our office today.

1)If you are in United States, we ship your order via USPS First
Class mail Internationl. The estimated the delivery time is about
7~10 days.

2)If you are outside of United States, we ship your order via
standard air mail.

The delivery shipping time is about 20~35 days according to your
countries.

I lived in the States for 30 years before returning to Canada. I sure
miss the fast postal service you have down there. A letter across town
usually went overnight. Here, it takes 5 business days. That means you
have to add two more days for the weekend:)

Mike

[Mike]

John S <sop...@invalid.org> wrote:

> Errr... The Wizard only tests ESR, yes? I don't think a comparison is
> possible under the circumstances.

<G> Yes, the comparison is a bit unfair, especially when the Wizard costs
more depending on where you buy it.

> If the TH2821A performs to the specs, then the money is minor and the
> Wizard looses miserably.

The TH2821A is an incredible value for the price. Apparently it is no
longer being produced by Tonghui, and the TH2822 is much more expensive. So
perhaps they are dropping the price to clear out the remaining inventory.

According to an email I just received on the top853 USB universal
programmer, apparently they ship via USPS to the States. So you might get
yours a lot sooner, maybe 2 weeks instead of a month.

> John S

Mike

[k...@att.bizzzzzzzzzzzz]

On Wed, 09 Nov 2011 16:42:52 GMT, Mike <sp...@me.not> wrote:

>"k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> wrote:
>
>> On Tue, 08 Nov 2011 22:29:40 GMT, Mike <sp...@me.not> wrote:
>>
>>>
>>>John S <sop...@invalid.org> wrote:
>>>
>>>> Hey, Mike -
>>>>
>>>> How long did it take to get your meter?
>>>
>>>> John S
>>>
>>>I ordered it on Thu, 8 Sep 2011, it was shipped within a day or so,
>>>and it arrived on Mon, 3 Oct 2011.
>>>
>>>That is about normal for shipments from China to Ontario, Canada. You
>>>will probably see faster delivery in the US. I forget which delivery
>>>service they used. Maybe it was DHL.
>>
>> Slow boat. ;-) I had a laptop (Lenovo) shipped from China on a
>> Monday (China time) and it was delivered on that Wednesday, noonish,
>> to my home in Alabama. It came UPS.
>
>I am in Canada, the land of polar bears and dog sleds. It snows here.

It snows here, too. Twice last year, in fact. Scares the crap outta the
natives. ;-)

>I just ordered the top853 USB universal programmer mentioned by Nico
>Coesel, http://www.ebay.com/itm/160378432470

Neat.

>I just received the following email from them:
>
> We shipped YOUR item from our office today.
>
> 1)If you are in United States, we ship your order via USPS First
> Class mail Internationl. The estimated the delivery time is about
> 7~10 days.

It is amazing. DealXtreme ships to the US via airmail for a couple of
dollars. It doesn't take anywhere near a week.

> 2)If you are outside of United States, we ship your order via
> standard air mail.
>
> The delivery shipping time is about 20~35 days according to your
> countries.
>
>I lived in the States for 30 years before returning to Canada. I sure
>miss the fast postal service you have down there. A letter across town
>usually went overnight. Here, it takes 5 business days. That means you
>have to add two more days for the weekend:)

Next day within the state. If they had anyone who knew how to run a business
maybe they wouldn't be going under.

[John S]

On 11/8/2011 4:29 PM, Mike wrote:

> John S<sop...@invalid.org> wrote:
>
>> Hey, Mike -
>>
>> How long did it take to get your meter?
>
>> John S
>
> I ordered it on Thu, 8 Sep 2011, it was shipped within a day or so, and it
> arrived on Mon, 3 Oct 2011.
>
> That is about normal for shipments from China to Ontario, Canada. You will
> probably see faster delivery in the US. I forget which delivery service
> they used. Maybe it was DHL.
>
> I really like the dissipation factor on electrolytics. You don't have to
> measure the ESR, then go to a lookup table to figure out if that is the
> proper value for the capacitance.

I was not aware that there was a lookup table for this. Even if I don't
need it, I'd like to see it. Where can I find it?

> I just look at the dissipation factor, and if it's greater than about 0.2
> for an older cap, toss it. This is a big time saver.
>
> Mike

How did you determine a D of 0.2 is the limit? Tell me more about D and
ESR, please.

John S

[John S]

On 11/9/2011 10:42 AM, Mike wrote:
> "k...@att.bizzzzzzzzzzzz"<k...@att.bizzzzzzzzzzzz> wrote:
>
>> On Tue, 08 Nov 2011 22:29:40 GMT, Mike<sp...@me.not> wrote:
>>
>>>
>>> John S<sop...@invalid.org> wrote:
>>>
>>>> Hey, Mike -
>>>>
>>>> How long did it take to get your meter?
>>>
>>>> John S
>>>
>>> I ordered it on Thu, 8 Sep 2011, it was shipped within a day or so,
>>> and it arrived on Mon, 3 Oct 2011.
>>>
>>> That is about normal for shipments from China to Ontario, Canada. You
>>> will probably see faster delivery in the US. I forget which delivery
>>> service they used. Maybe it was DHL.
>>
>> Slow boat. ;-) I had a laptop (Lenovo) shipped from China on a
>> Monday (China time) and it was delivered on that Wednesday, noonish,
>> to my home in Alabama. It came UPS.
>
> I am in Canada, the land of polar bears and dog sleds. It snows here.

You have my sympathies (unless you like that climate). I live near
Dallas, Texas where the weather can go from 110F in the summer to
(rarely) 10F in the winter. We are having a historical drought right
now. At the moment it is 68F and sunny. I've entertained the idea of
moving to Belize.

> I lived in the States for 30 years before returning to Canada. I sure
> miss the fast postal service you have down there. A letter across town
> usually went overnight. Here, it takes 5 business days. That means you
> have to add two more days for the weekend:)
>
> Mike

That is the major reason I have rejected the idea of moving to Belize. I
am in the habit of getting the things I want from Mouser or Digikey or
whatever in a couple of days. That wouldn't happen down there.

John S

[Mike]

John S <sop...@invalid.org> wrote:

> I was not aware that there was a lookup table for this. Even if I
> don't need it, I'd like to see it. Where can I find it?

>> I just look at the dissipation factor, and if it's greater than
>> about 0.2 for an older cap, toss it. This is a big time saver.

>> Mike

> How did you determine a D of 0.2 is the limit? Tell me more about
> D and ESR, please.

> John S

Hi John,

most of the ESR meters print a table on the front panel that shows
the expected ESR for different values of caps. There are some
examples on this page:

http://members.ozemail.com.au/~bobpar/esrmeter.htm

The Capacitor Wizard doesn't have a table. Instead, it has some
vague instructions by Doug Jones, the designer of the Capacitor
Wizard. Here is a section from one of the pdf files:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Well, finding those open caps and good caps was easy. Now lets look
at other bad caps that require a little more experience with the
Capacitor Wizard and some knowledge about capacitor TYPES and USES.

You probably found caps from 1 to 30 ohms ESR in your bad box. How
do you tell the good caps from the bad??

Whether the ESR of a particular capacitor is correct or too high can
always be determined by comparing the suspicious capacitor to a
known good one of the same value, voltage rating, and type.

Unfortunately one doesn't always have another capacitor to compare
against. Experience is the best teacher here, however there are some
general guidelines:

The higher the rated working voltage, the higher the normal ESR.

Capacitors used in Power Switching applications need to have really
LOW ESR - less than 1/2 ohm Nonpolar Caps are normally less than 1/2
ohm The next logical question about ESR is "How HIGH is TOO HIGH"?

Thats a judgement call that can only be based on experience or
comparison to a known good cap (or access to the engineering data
from the capacitor or equipment manufacturer - ha ha!). Over 10 ohms
is certainly too high for most applications. Over 3 ohms is too high
for Horiz/Vert switching applications. Over 1/2 ohm is too high for
power switching applications. By comparison you will gain experience
and know when to be suspicious. These are my opinions. Here are some
actual repair situations:

Example: 47uf @50vdc measures 25 ohms ESR in circuit - BAD CAP The
suspect capacitor is a 47uf @50vdc in a switching power supply for a
VCR. The Capacitor Wizard has measured 25 ohms ESR in circuit. That
is higher than 15 ohms and much to high for any quality cap. A new
capacitor measured 5 ohms ESR. The new capacitor fixed the VCR. In
my opinion the new capacitor was not of the highest quality (5 ohms
is too high) however it did fix the VCR. The use of these low
quality inexpensive import capacitors is probably the reason we see
so much capacitor failure in con- sumer electronic equipment! A
higher quality cap with a lower ESR of the same kind costs more
money but will measure less than 1 ohm and be more reliable.

Conclusion: This is a higher voltage capacitor and can be expected
to normally measure higher than 1/2 ohm. In my judgment any "switch
mode" capacitor that measures more than 3 ohms ESR is suspect no
matter what the voltage rating.

However you may obviously get by with the 5 ohms ESR in that
particular circuit. For comparison, the bad part was checked "out of
circuit" on a well known competitors $2000 Cap analyzer and it
determined that the cap was GOOD - even though the ESR measured 25
ohms! That manufacturer made a huge mistake by trying to calculate
good and bad ESR from entered and measured data. It can't be done
reliably. That is why we don't simply have a good/bad indication on
our meter scale. Any cap over 3 ohms is suspect. This is my
Experience.

Example: 1000uf @6vdc measures 1.5 ohms in circuit - BAD CAP This is
a little brown 1000uf 6vdc cap used in lots of VCR switching power
supplies. The Capacitor Wizard measured 1.5 ohms in circuit. Because
the capacitors operating voltage is so low (6vdc) and its used in a
switching power supply, I would expect a normal ESR reading of less
than 1/2 ohm. Comparison to a known good cap confirmed it should
measure less than 1/2 ohm. Replacing this cap cured the trouble.

This particular cap goes bad often as I have many in my box of bad
caps gathered from local repair compa- nies. If you work on VCRs, I
bet you have some too.

Summery: (mrm: sp)

Measuring ESR is a very good indicator of capacitor failure. For
switch mode circuits it is the ONLY reliable capacitor test, IN or
OUT of circuit!. Open caps and caps with really high ESR (over 10
ohms) are easy to find in circuit and need to be replaced.

Marginal caps that measure between 1 and 10 ohms ESR require some
experience with the Capacitor Wizard and/or comparison to a known
good cap of the same voltage, value, and type. Caps above an
operating voltage of 35vdc have a normally higher ESR (around 1 to 3
ohms) than caps of a lower voltage (less than 1/2 ohm ESR).

I know of no perfect formula or rule that can always tell normal ESR
from marginal ESR other than comparison to a known good part. The
obvious solution is to obtain the capacitor manufacturers data
manuals on the EXACT capacitor measured but that is not normally
practical. As a technician myself I always follow this rule: "If in
doubt, replace". You will eliminate a lot of recalls and cure many
weird and undefinable intermittent problems if you follow this rule.

Doug Jones, Designer of the Capacitor Wizard

http://midwestdevices.com/_pdfs/FirstTime.pdf

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To find a typical dissipation factor for the Tonghui, I went through
several boxes of old electrolytic caps. Regardless of the capacitor
value, there seemed to be a clear dividing line between good and bad
caps. I settled on D = 0.2 as it seemed to be a reasonable number
for most applications, such a bypass and coupling caps.

However, if the application was critical, such as a capacitance
multiplier for low level dc supply, I'd look for capacitors with the
lowest D value I could find, and put some in parallel.

The interesting thing, and this has me a bit confused, is the
dissipation factor does not seem to be affected much by the test
frequency.

I would expect the ESR to remain fairly constant with frequency, but
the capacitive reactance of course will change. So the impedance of
the capacitor will change with frequency, and I would expect the
dissipation factor to change also.

I haven't had time to sort this out yet, and I need to get some more
experience with this instrument and find out how it is making the
measurement. For example, take a known good capacitor and add some
series resistance and see what happens to the readings. But here are
some wikipedia references to start with:

Equivalent series resistance

http://en.wikipedia.org/wiki/Equivalent_series_resistance

Dissipation factor

http://en.wikipedia.org/wiki/Dissipation_factor

Mike

[Mike]

John S <sop...@invalid.org> wrote:

> On 11/9/2011 10:42 AM, Mike wrote:

>> I am in Canada, the land of polar bears and dog sleds. It snows here.

> You have my sympathies (unless you like that climate). I live near
> Dallas, Texas where the weather can go from 110F in the summer to
> (rarely) 10F in the winter. We are having a historical drought right
> now. At the moment it is 68F and sunny. I've entertained the idea of
> moving to Belize.

Winter is not so bad. You get used to digging your car out of snowbanks
and scraping ice from the windshield. There were two things I didn't like
much about the states. One was the smog in most cities. That started to
make me sick. Now I can't even go near Toronto when it is bad.

The other was teenagers with 9 mm and .45 firing them in alleways at
night. I got a scanner and started listening to the police trying to
catch them. I guess they had scanners also, since I never heard of anyone
getting caught.

The nights are very quiet here in Midland, Ontario. The police
transmissions are encrypted, so it's a waste of time trying to listen. I
used to be able to tell the difference between a 9 mm and a .45, but I
haven't heard one for such a long time that I probably forgot what they
sound like.

>> I lived in the States for 30 years before returning to Canada. I sure
>> miss the fast postal service you have down there. A letter across town
>> usually went overnight. Here, it takes 5 business days. That means you
>> have to add two more days for the weekend:)
>>
>> Mike
>
> That is the major reason I have rejected the idea of moving to Belize.
> I am in the habit of getting the things I want from Mouser or Digikey
> or whatever in a couple of days. That wouldn't happen down there.
>
> John S

I'd move to Bangkok in an instant. Except right now they are having
problems with flooding. But you can get just about any electronic
component in minutes, at very cheap prices. And the girls are soooo
nice:)

Mike

[John S]

On 11/11/2011 4:05 PM, Mike wrote:
> John S<sop...@invalid.org> wrote:
>

> Winter is not so bad. You get used to digging your car out of snowbanks
> and scraping ice from the windshield. There were two things I didn't like
> much about the states. One was the smog in most cities. That started to
> make me sick. Now I can't even go near Toronto when it is bad.

Yeah. I'm on the north side of Dallas and I can smell the fumes when I
go outside.

> The other was teenagers with 9 mm and .45 firing them in alleways at
> night. I got a scanner and started listening to the police trying to
> catch them. I guess they had scanners also, since I never heard of anyone
> getting caught.

Don't have that around here yet, thankfully.

> The nights are very quiet here in Midland, Ontario.

Usually quiet here, too, except for the annoying loud bass thumping from
cars driving by.

>> That is the major reason I have rejected the idea of moving to Belize.
>> I am in the habit of getting the things I want from Mouser or Digikey
>> or whatever in a couple of days. That wouldn't happen down there.
>>
>> John S
>
> I'd move to Bangkok in an instant. Except right now they are having
> problems with flooding. But you can get just about any electronic
> component in minutes, at very cheap prices. And the girls are soooo
> nice:)
>
> Mike

I have friends who are pushing me to retire to the Philippines. They say
I can have one or more live-in maids, a beachfront house, etc for less
than my monthly costs now. It is persuasive.

[Spehro Pefhany]

On Fri, 11 Nov 2011 16:43:08 -0600, the renowned John S
<sop...@invalid.org> wrote:

>
>I have friends who are pushing me to retire to the Philippines. They say
>I can have one or more live-in maids, a beachfront house, etc for less
>than my monthly costs now. It is persuasive.

Foreigners are not allowed to own land in the Philippines, let alone
beachfront property, which is probably just as well. Long term leases
(eg. 50 years) are possible.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[John S]

On 11/11/2011 4:53 PM, Spehro Pefhany wrote:
> On Fri, 11 Nov 2011 16:43:08 -0600, the renowned John S
> <sop...@invalid.org> wrote:
>
>>
>> I have friends who are pushing me to retire to the Philippines. They say
>> I can have one or more live-in maids, a beachfront house, etc for less
>> than my monthly costs now. It is persuasive.
>
> Foreigners are not allowed to own land in the Philippines, let alone
> beachfront property, which is probably just as well. Long term leases
> (eg. 50 years) are possible.
>
>
> Best regards,
> Spehro Pefhany

I'm 70. I don't need to own anything anywhere. I'm renting life (and
beer) as it is.

[John S]

On 10/31/2011 9:58 PM, Mike wrote:
> Here's something that may interest some folks here. I just got my new
> Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed.

Hey, Mike -

Mine came in yesterday. Since the wall wart is 220V, it is useless to me
so I cut the chord and used a lab power supply to charge it. This got
interesting.

With the meter off, the current was only about 5mA. I turned the meter
on and the current went to about 140mA. After a period of time which I
did not measure, the current dropped back to about 50mA and the battery
symbol indicated full charge.

This makes me wonder if fast charge takes place only when the meter is
on and it just trickle charges with the meter off. Have you noticed a
long charging time with the meter off?

Cheers,
John S

[Jon Kirwan]

On Sat, 19 Nov 2011 13:13:58 -0600, John S
<sop...@invalid.org> wrote:

>On 10/31/2011 9:58 PM, Mike wrote:
>> Here's something that may interest some folks here. I just got my new
>> Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed.
>

>Mine came in yesterday. Since the wall wart is 220V, it is useless to me
>so I cut the chord and used a lab power supply to charge it. This got
>interesting.

Ordered mine _after_ you and got mine a week ago, partly
because I asked them to rush it and they responded by saying
they'd heard me and would work quickly. I mentioned that I
was US 60Hz 120V, failing to find anything on the topic on
the web page, and received email saying that they'd look into
it and figure something out.

When it arrived, they had included another wall-wart (about
six times heavier and much larger than the one that comes in
the package) without a cord but instead an interesting power
socket that the "regular" 220V wall wart could plug into. No
charge. Just had to ask.

Manual is in chinese, had to download an English version.

>With the meter off, the current was only about 5mA. I turned the meter
>on and the current went to about 140mA. After a period of time which I
>did not measure, the current dropped back to about 50mA and the battery
>symbol indicated full charge.
>
>This makes me wonder if fast charge takes place only when the meter is
>on and it just trickle charges with the meter off. Have you noticed a
>long charging time with the meter off?

I noticed a long charge time when off, but a significantly
shorter charge time when on. I hadn't measured the current,
though, probably because I didn't need to hack my power
supply into bits before using it.

System came up in 'delta' mode, whihc caused me confusion
despite seeing the symbol there telling me what probably was
going on. I knew what was probably causing the odd readings
but until I got the English version manual, I wasn't entirely
sure what else to correctly do to fix it. While playing with
that before reading the manual, I did uncover how to
auto-calibrate it in 'short' and 'open' mode, though.

So far, it's been very nice and I've been impressed with what
was included at the price -- including the extra, weighty 110
to 220 wall wart. But I've yet to put it to serious use. I
have used it to help quickly figure out the core material
types of some randomly collected toroids I have in a drawer,
using some windings and calcs. Time will tell, but happy for
now.

Jon

[John S]

Thanks for your input, Jon.

I'm pretty sure it will charge faster (based on my amperage readings)
when power is applied.

I've been subjecting it to tests as well as I can muster. I have a
Boonton 71K capacitance meter that I used as a "standard". I have a
.01uF, 1% cap Wima cap that I bought because it was the lowest D I could
find. The Boonton agrees with the 2821A as best as my eyes will make out
considering that the Boonton has an analog meter.

I have a Xicon 18 ohm, 25 watt resistor I measured. In inductance mode,
it showed 2.95uH and a Q of .0105 at 10kHz. That calculates to give a
series R of about 17.65 ohms. So I then measured the resistance with the
2821 (in the resistance mode) to be 17.73 ohms. Well, then I fired up my
HP3456A and measured the resistance at 17.75 ohms.

I am impressed. So far, it has been correct for every test I can give it
considering my limited standards situation. Oh, wait! I have some .1%
resistors I checked with it. I didn't record the readings, but they were
well withing the .1%.

I don't know how they do it.

John S

[Mike]

Jon & John,

Sorry for the delay. Have been quite ill.

It looks like they sent Jon a 110V to 220V step up transformer. That
would explain the weight. After complaining about not being able to run
on 110V, they sent me a small, lightweight 110V switching power supply
that looked similar to the original 220V unit. I'm surprised they did not
send you both the same transformer instead of the 220V version.

I did the initial charging with the instrument turned off. After about 4
hours, it indicated full charge. But I had been playing with it trying to
figure out how it worked until I finally decided there was an internal
battery that needed charging. So it got at least a partial charge while I
was fooling around.

I found the instrument may do strange things until it is fully charged.
This makes sense if you consider the uP may not be getting the correct
voltage during the initial charging cycle. After it was fully charged, it
stopped doing silly things and started giving good results.

Thanks to John for the calibration info. I was also quite impressed with
the performance. It is quite outstanding, especially for the price. I
think we will get many years of useful work from these units. But I have
to caution everyone to make absolutely certain any capacitor is fully
discharged before measuring it. I lost a good LCR meter by accidentally
losing track of which capacitors were discharged and which were still
fully charged. It made a dull thud and stopped working.

So we can't depend on ourself to protect the unit. There has to be
dedicated protection circuity.

I'm thinking of making a small adapter with a discharge resistor and a
power bridge rectifier across the input terminals. I found the instrument
did not respond to having a single diode across the capacitor, so a
bridge should have no effect. I'll add a SPDT switch so the dump resistor
is normally in the circuit, and have the bridge rectifier across the
terminals to the instrument as insurance.

Thanks,

Mike

[John S]

> Jon& John,

Good to hear from you, Mike. I hope you are recovering rapidly from your
illness.

One thing I learned that you may or may not know is, when measuring
capacitors, you can switch to the R mode and read the capacitor's ESR
directly rather than having to calculate it from D. I was truly pleased
to discover that.

When I received my meter, I cut the cord off of the 220V wall wart and
used the cord and a lab power supply to charge the meter while watching
the current. Very interesting. Unless I did something wrong, I found
that the meter will not charge at more than a few mA when in the "off"
condition. So, I turned it on and watched the charging current until it
took a drop and the bars on the display indicated "full".

The vendor did send me a 120V supply. I have not used it yet, and I
think I will charge the meter next time just as I did last time (with a
lab supply) and make more measurements until I am comfortable that I
have a good feel for the meter's charging characteristics.

Cheers,
John S

[Mike]

==

John S <Sop...@invalid.org> wrote:

> Good to hear from you, Mike. I hope you are recovering rapidly
> from your illness.

Thanks very much. It will be a continual struggle but I'm starting
to get a handle on things.

> One thing I learned that you may or may not know is, when
> measuring capacitors, you can switch to the R mode and read the
> capacitor's ESR directly rather than having to calculate it from
> D. I was truly pleased to discover that.

Yes, I discovered that also. I thought it was just a quirk, but it
did seem to work reliably on capacitors. BTW, I did find the ESR
does decrease rapidly with frequency at low frequencies. It starts
to remain constant around 10KHz and above. So the Q does appear to
remain the same with different test frequencies below 1KHz. You can
see the effect by looking at any electrolytic datasheet.

> When I received my meter, I cut the cord off of the 220V wall wart
> and used the cord and a lab power supply to charge the meter while
> watching the current. Very interesting. Unless I did something
> wrong, I found that the meter will not charge at more than a few
> mA when in the "off" condition. So, I turned it on and watched the
> charging current until it took a drop and the bars on the display
> indicated "full".

The charging arrangment seems strange. It looks like they wanted to
simplify things by leaving it in trickle charge when it is turned
off, then they simply put the charger, the battery, and the
instrument in parallel when you turn it on.

I don't even know what kind of battery is inside. I don't think a
NiCd will trickle charge at 5mA, and most of the more exotic
batteries require special charging circuits to prevent destruction.
Maybe I'll take mine apart this weekend and have a look.

> The vendor did send me a 120V supply. I have not used it yet, and
> I think I will charge the meter next time just as I did last time
> (with a lab supply) and make more measurements until I am
> comfortable that I have a good feel for the meter's charging
> characteristics.

First step is to find out what kind of battery is inside. OK, you
talked me into doing it now.

Pfaff! First thing I do is drop a screw on the floor. Took five
minutes to find it!

The battery is a 200mA/hr 8.4V NiMh. Here's the datasheet:

http://www.rapidonline.com/pdf/18-4168.pdf

It looks like it wants 20mA for 14~16h. I don't think 140mA is going
to do it much good:)

But I'm surprised that you only measure 5mA with it turned off. What
voltage are you delivering to the unit?

> Cheers,
> John S

Thanks,

Mike

[John S]

Thanks for the great information!

> It looks like it wants 20mA for 14~16h. I don't think 140mA is going
> to do it much good:)

A bit scary, huh.

> But I'm surprised that you only measure 5mA with it turned off. What
> voltage are you delivering to the unit?

I set the lab supply to 12V.

Here is the data I took:

Time Meter mA Notes

19:21 Off 3.55 Battery indicator at 1 bar
19:32 On 143 Battery indicator at 1 bar
19:40 On 136 Battery alternating between 1 bar and 2 bars
19:44 On 135 Battery at 2 bars
20:27 On 138 Battery alternating between 2 bars and 3 bars
20:19 On 140 Battery at 3 bars
21:02 On 27 Battery at 3 bars
21:06 On 33 Battery at 3 bars
21:10 On 38 Battery at 3 bars
21:15 On 41 Battery at 3 bars
21:20 On 42 Battery at 3 bars

[John S]

On 1/10/2012 3:37 AM, Mike wrote:

>

> It looks like it wants 20mA for 14~16h. I don't think 140mA is going
> to do it much good:)

BTW, Mike, one of the recommended batteries in the back of the manual is
a GP20R8H. Take a look at those specs.

John S

[Mike]

John S <Sop...@invalid.org> wrote:

>> It looks like it wants 20mA for 14~16h. I don't think 140mA is
>> going to do it much good:)

> A bit scary, huh.

>> But I'm surprised that you only measure 5mA with it turned off.

>> What voltage are you delivering to the unit?

> I set the lab supply to 12V.

> Here is the data I took:

> Time Meter mA Notes

> 19:21 Off 3.55 Battery indicator at 1 bar
> 19:32 On 143 Battery indicator at 1 bar
> 19:40 On 136 Battery alternating between 1 bar and 2 bars
> 19:44 On 135 Battery at 2 bars
> 20:27 On 138 Battery alternating between 2 bars and 3
bars
> 20:19 On 140 Battery at 3 bars
> 21:02 On 27 Battery at 3 bars
> 21:06 On 33 Battery at 3 bars
> 21:10 On 38 Battery at 3 bars
> 21:15 On 41 Battery at 3 bars
> 21:20 On 42 Battery at 3 bars

Thansk for the excellent data!

Obviously the battery isn't charging very heavily with the unit
turned off. Maybe that is just a trickle charge to keep the battery
topped up.

With the unit turned on, it looks like they are really charging the
battery at 140mA. It is amazing how the current snaps off at 21:02

I wonder if the 40mA drain with the unit turned on is the normal
power drain for the instrument. Actually that's not too bad
considering what's inside.

I guess the other thing is NiMh has a pretty severe self-discharge
curve. It looks like the unit would have to remain plugged in on
standy to keep the battery trickle-charged. Otherwise it would have
to go through the complete 140mA charge cycle every time we turn it
on. And while it is charging, it may be be usable due to the funny
readings.

It turns out some of this information is available in the manual at

"http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation%
20Manual.pdf"

Section 3.3 on page 30 talks about battery recharge. They state it
takes 2~3 hrs to charge, and this gives 5~6 hrs of use. They also
state twice that it may not operate correctly while charging, which
I already found out by trying to fiddle with the unit when it first
arrived.

If the battery has 200mAh, and it lasts 5 hrs, that's about 40mA,
which is what you measured in the table above. So it is beginning to
make some sense.

So, it has a battery, which is nice. But the battery turns out to be
a hassle if we are not using the unit constantly, which is a bit of
a pain.

Since we cannot predict when we are going to need the unit, it looks
like it will have to stay on trickle charge all the time. That's not
much of a problem. It doesn't take much power, but probably the
biggest hassle will be finding a spare plug.

Further update on the Q of electrolytics. I found some curves on
ESR vs Frequency in Fig. 1 - 11 of Impedance, ESR vs. Frequency
Characteristics. This is on page 7 of

http://www.nmr.mgh.harvard.edu/~reese/electrolytics/tec1.pdf

What this says is the ESR curve decreases as the frequency
increases, and doesn't start to flatten until we reach about 10KHz.

Below that, the ESR increases as we lower the frequency. Since the
capacitive reactance is also decreasing, the Dissipation Factor, or
Q, will tend to remain constant. And that's what the Tonghui is
showing.

I never knew that.

Also, did you notice there is a black strip along the top of the
unit? That looks like it might be part of an IR data port. I didn't
take the unit completely apart since there was somethng snagging it.

But next time I go in, I will try to see if there is anything
mounted in that area that might be of interest.

Thanks,

Mike

[Mike]

OK, I'm looking at http://www.gpina.com/pdf/GP20R8H_DS.pdf

It shows the same 20 mA for 16 hrs as recommended for this battery. It
also shows the fast charge cycle, which requires a charge control
circuit. They give the following parameters:

Fast Charge : 100 mA to 200 mA (0.5 to 1C)
charge termination control recommended
control parameters:
-dV : 0 - 35mV
DT/dt ** : 0.8 o C/min (0.5 to 0.9C)
: 0.8 - 1 o C/min (1C)
TCO ** : 45 - 50 o C

So it looks like they really do intend to do a fast charge. Also, there
was no temperature sensor anywhere near the battery when I took it
apart, so maybe they are relying on the delta V hump at full charge. I'm
not sure how they keep track of things when the user (me) keeps turning
the unit on and off, but they do seem to be able to charge the battery
since the charge indicator appears to work well.

So it seems they do have things under control. That's good. Gives more
confidence that it will continue working as the battery ages.

Thanks for the headsup.

Mike

[John S]

On 1/10/2012 5:04 PM, Mike wrote:
> Thansk for the excellent data!

My pleasure. I wasn't trying very hard. I'll do better next time.

> Obviously the battery isn't charging very heavily with the unit
> turned off. Maybe that is just a trickle charge to keep the battery
> topped up.
>
> With the unit turned on, it looks like they are really charging the
> battery at 140mA. It is amazing how the current snaps off at 21:02

Well, the snap-off occurred somewhere between 20:19 and 21:02. I'll try
to nail it down a bit better next time.

> I wonder if the 40mA drain with the unit turned on is the normal
> power drain for the instrument. Actually that's not too bad
> considering what's inside.

I believe you are correct. It was my suspicion as well.

> I guess the other thing is NiMh has a pretty severe self-discharge
> curve. It looks like the unit would have to remain plugged in on
> standy to keep the battery trickle-charged. Otherwise it would have
> to go through the complete 140mA charge cycle every time we turn it
> on. And while it is charging, it may be be usable due to the funny
> readings.

Actually, I took that data on 11/20/2011. I have not charged it since
then and it still shows two battery bars remaining. I have used it only
occasionally, maybe an hour total, since then. I'm pleased that it is
holding up so well.

> It turns out some of this information is available in the manual at
>
> "http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation%
> 20Manual.pdf"

Yes. I got that manual when you provided the link to me weeks ago.
Thanks again. As I mentioned in another post, take a look at the
recommended GP20R8H specs as mentioned on page 31. It makes me breathe
easier.

> Section 3.3 on page 30 talks about battery recharge. They state it
> takes 2~3 hrs to charge, and this gives 5~6 hrs of use. They also
> state twice that it may not operate correctly while charging, which
> I already found out by trying to fiddle with the unit when it first
> arrived.
>
> If the battery has 200mAh, and it lasts 5 hrs, that's about 40mA,
> which is what you measured in the table above. So it is beginning to
> make some sense.
>
> So, it has a battery, which is nice. But the battery turns out to be
> a hassle if we are not using the unit constantly, which is a bit of
> a pain.
>
> Since we cannot predict when we are going to need the unit, it looks
> like it will have to stay on trickle charge all the time. That's not
> much of a problem. It doesn't take much power, but probably the
> biggest hassle will be finding a spare plug.

I've not had a problem with battery self-discharge, as I mentioned
above. I do not leave mine charging all the time, but it might not be a
bad thing.

> Further update on the Q of electrolytics. I found some curves on
> ESR vs Frequency in Fig. 1 - 11 of Impedance, ESR vs. Frequency
> Characteristics. This is on page 7 of
>
> http://www.nmr.mgh.harvard.edu/~reese/electrolytics/tec1.pdf
>
> What this says is the ESR curve decreases as the frequency
> increases, and doesn't start to flatten until we reach about 10KHz.

Yes. I discovered the same thing with the meter and in a CDE paper:

www.cde.com/catalogs/AEappGUIDE.pdf

Thanks for your link. I've saved the file.

> Below that, the ESR increases as we lower the frequency. Since the
> capacitive reactance is also decreasing, the Dissipation Factor, or
> Q, will tend to remain constant. And that's what the Tonghui is
> showing.
>
> I never knew that.

Neither did I. It gives me a good feeling that the meter is telling me
the things I want to know.

> Also, did you notice there is a black strip along the top of the
> unit? That looks like it might be part of an IR data port. I didn't
> take the unit completely apart since there was somethng snagging it.

Yes, I did. I'm sure it is a data port. I saw something in the manual
about reserved function concerning that. For example, see the last
bullet on page 5 of the manual.

> But next time I go in, I will try to see if there is anything
> mounted in that area that might be of interest.
>
> Thanks,
>
> Mike

I'm certain you'll find IR emitter and detector.

It's possible that the contributors on this group don't care about our
detailed discussions. I will give you a temporary email address whereby
you can reach me and we can then privately exchange more permanent
addresses, if you like.

tonghui dot meter dot is_nice at xoxy dot net

Cheers,
John S

[John S]

I agree. And, you're welcome. Nice to have someone to compare notes with.

John S

[Mike]

John S <Sop...@invalid.org> wrote:

> On 1/10/2012 5:04 PM, Mike wrote:

>> Thansk for the excellent data!

> My pleasure. I wasn't trying very hard. I'll do better next time.

You really did fantastic! That's what opened this whole subject.

[...]

>> Otherwise it would have to go through the complete 140mA charge
>> cycle every time we turn it on. And while it is charging, it may
>> be be usable due to the funny readings.

> Actually, I took that data on 11/20/2011. I have not charged it
> since then and it still shows two battery bars remaining. I have
> used it only occasionally, maybe an hour total, since then. I'm
> pleased that it is holding up so well.

I think my original problem started when I tried to operate the unit
with a completely dead battery. That may have dropped the voltage to
the uP enough to give the erratic results I was getting.

Now I'm thinking as long as there is some charge remaining in the
battery, it should work fine while it is charging.

So I think it probably can sit on the shelf for long periods when it
is not needed, and still be ready for use when it is required for a
new project.

Apparently NiMh shares some of the same features as regular NiCd,
and it doesn't particularly care what state of charge it is in. The
fast charge cycle that your measurements show probably charges the
cell at 100mA, with the other 40mA going to the electronics.

That amount of charge is well within the recommended limits for the
battery, so I think the designers have done a good job to give a
long life to the battery, and it should not be a concern. New ones
are available for $5.00 if you shop around, and some sales might
even drop that to $1.50. So I'm not worried about the battery life
or replacement cost any more. I think we should just use the unit
when it is needed, and leave it on the shelf the rest of the time.

[...]

> It's possible that the contributors on this group don't care about
> our detailed discussions. I will give you a temporary email
> address whereby you can reach me and we can then privately
> exchange more permanent addresses, if you like.

> tonghui dot meter dot is_nice at xoxy dot net

Thanks, John. That would be a special privilege. But recall that Jon
Kirwan has a unit, and P E Schoen has the MCP BR2822 which appears
to be identical:

http://www.multimeterwarehouse.com/BR2822f.htm

So there are some who might be interested in the discussions, and
maybe others who might be interested in getting one also. But if we
disappear, no one else will be able to find out more about it.

What I would like to do is find out more about how this thing works
and why it is so accurate. Is it because of good snr, good
circuitry, quality a/d's, software, components, or some other
factor. What can we learn from this instrument that can help in
other projects?

But there are times when the readings fluctuate for no apparent
reason. I'd also like to find out why it does that and what can be
done to overcome the problem. The new model has averaging, so that
would help. But it probably slows down the measurement, and it also
costs much more. Is there any way we can get the same effect without
the added cost?

And I certainly would not mind modifying my instrument if if would
improve the performance. For me, that is a given.

Someone may come across a piece of information or some data that
helps unravel these mysteries, and post it here. But if we go
private, this is unlikely to happen.

We are not taking up much room, and we are not bothering anyone, so
my vote is to stay here and not worry.

[John S]

Sounds good to me.

> [...]
>
> > It's possible that the contributors on this group don't care about
> > our detailed discussions. I will give you a temporary email
> > address whereby you can reach me and we can then privately
> > exchange more permanent addresses, if you like.
>
>

> Thanks, John. That would be a special privilege. But recall that Jon
> Kirwan has a unit, and P E Schoen has the MCP BR2822 which appears
> to be identical:
>
> http://www.multimeterwarehouse.com/BR2822f.htm
>
> So there are some who might be interested in the discussions, and
> maybe others who might be interested in getting one also. But if we
> disappear, no one else will be able to find out more about it.
>
> What I would like to do is find out more about how this thing works
> and why it is so accurate. Is it because of good snr, good
> circuitry, quality a/d's, software, components, or some other
> factor. What can we learn from this instrument that can help in
> other projects?
>
> But there are times when the readings fluctuate for no apparent
> reason. I'd also like to find out why it does that and what can be
> done to overcome the problem. The new model has averaging, so that
> would help. But it probably slows down the measurement, and it also
> costs much more. Is there any way we can get the same effect without
> the added cost?

It fluctuates around zero quite a bit when I check the resistance of an
8200pF, c0g MLCC capacitor. However, I think it is because the
resistance is so low. The cap showed a D of .0000 to .0001 so it was
pushing the limits. The capacitance reading is steady.

> And I certainly would not mind modifying my instrument if if would
> improve the performance. For me, that is a given.
>
> Someone may come across a piece of information or some data that
> helps unravel these mysteries, and post it here. But if we go
> private, this is unlikely to happen.
>
> We are not taking up much room, and we are not bothering anyone, so
> my vote is to stay here and not worry.
>
>

> Thanks,
>
> Mike

You make some good, valid points. I agree.

John S

[josephkk]

On Tue, 10 Jan 2012 23:04:48 GMT, Mike <sp...@me.not> wrote:

>
> Obviously the battery isn't charging very heavily with the unit
> turned off. Maybe that is just a trickle charge to keep the battery
> topped up.
>
> With the unit turned on, it looks like they are really charging the
> battery at 140mA. It is amazing how the current snaps off at 21:02
>
> I wonder if the 40mA drain with the unit turned on is the normal
> power drain for the instrument. Actually that's not too bad
> considering what's inside.
>
> I guess the other thing is NiMh has a pretty severe self-discharge
> curve. It looks like the unit would have to remain plugged in on
> standy to keep the battery trickle-charged. Otherwise it would have
> to go through the complete 140mA charge cycle every time we turn it
> on. And while it is charging, it may be be usable due to the funny
> readings.
>
> It turns out some of this information is available in the manual at
>
> "http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation%
>20Manual.pdf"
>
> Section 3.3 on page 30 talks about battery recharge. They state it
> takes 2~3 hrs to charge, and this gives 5~6 hrs of use. They also
> state twice that it may not operate correctly while charging, which
> I already found out by trying to fiddle with the unit when it first
> arrived.

I tried the link and the resulting pdf has a problem and Adobe won't
render it. I there another English manual for it?

?-)

[josephkk]

On Thu, 12 Jan 2012 06:25:18 GMT, Mike <sp...@me.not> wrote:

>
> What I would like to do is find out more about how this thing works
> and why it is so accurate. Is it because of good snr, good
> circuitry, quality a/d's, software, components, or some other
> factor. What can we learn from this instrument that can help in
> other projects?
>
> But there are times when the readings fluctuate for no apparent
> reason. I'd also like to find out why it does that and what can be
> done to overcome the problem. The new model has averaging, so that
> would help. But it probably slows down the measurement, and it also
> costs much more. Is there any way we can get the same effect without
> the added cost?
>
> And I certainly would not mind modifying my instrument if if would
> improve the performance. For me, that is a given.
>
> Someone may come across a piece of information or some data that
> helps unravel these mysteries, and post it here. But if we go
> private, this is unlikely to happen.
>
> We are not taking up much room, and we are not bothering anyone, so
> my vote is to stay here and not worry.
>
> > Cheers,
> > John S
>
> Thanks,
>
> Mike

I'll buy some of that. These have just about the properties i am looking
for. So i am real interested.

?-)

[Mike]

josephkk <joseph_...@sbcglobal.net> wrote:

> I tried the link and the resulting pdf has a problem and Adobe won't
> render it. I there another English manual for it?
>
> ?-)

Hi Joseph,

I just tried the link and it worked fine. Maybe there was a glitch in the
download.

Here are three links that I just checked and they all work fine:

"http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation%
20Manual.pdf" (original link)

"http://www.4shared.com/office/HSPQhiv7/TH2821A_Operation_Manual.html"
(must wait 20 seconds)

"http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821A.pdf"
(secured - cannot copy text)

Mike

[Mike]

josephkk <joseph_...@sbcglobal.net> wrote:

> I'll buy some of that. These have just about the properties i am
looking
> for. So i am real interested.
>
> ?-)

If you want to find bad electrolytics, I don't think you can find a
better bargain. It gives the dissipation of the capacitor, so you don't
have to fool with lookup tables like you do with a conventional ESR meter
to see if the cap is good or bad. Besides giving an easy way to check
electrolytics, it also gives the capacitance value to four digits. No ESR
meter does that. It also measures inductors and resistors, which no ESR
meter can do. It has settable upper and lower limits for bin sorting. And
it's less expensive than most ESR meters that I could find.

I just checked eBay. On Jan 14, 2012, the lowest price was $159.99 with
$25.00 shipping. Another is available at C $187.99 and C $12.00 shipping,
so you have to check both carefully for the best deal.

I'd also get the TH26029 SMD Test Tweezer Probe for $29.99.

The newer model has averaging, but it is closer to $500. I don't think
it's worth considering. Once you start getting into those numbers, might
as well consider going to a more expensive bench model with greater
accuracy and frequency range.

If you order one, make certain to get a 120VAC adapter instead of the
220VAC one that normally comes with it. Get them to confirm that they
received your request and will comply.

Hope this helps.

Mike

[Mike]

Mike <sp...@me.not> wrote:

> If you want to find bad electrolytics, I don't think you can find
> a better bargain. It gives the dissipation of the capacitor, so
> you don't have to fool with lookup tables like you do with a
> conventional ESR meter to see if the cap is good or bad. Besides
> giving an easy way to check electrolytics, it also gives the
> capacitance value to four digits.

Update : it actually displays 4 digits plus a decimal on large
electrolytics. But the two least significant digits dance around a
lot.

I switched to a 10uF 250VAC +/-5% film capacitor, and it read
10.045uF with the last digit fluctuating between 4 and 6. So I
conclude electrolytics are not very stable. But the readings are
quite consistent on a quality part.

I've been monitoring the battery self-discharge. It is terrible. It
loses a significant fraction of the charge in a week. Leaving it
plugged in has no effect. It does not trickle charge while it is
turned off.

One solution might be to simply leave it plugged in a turned on. It
says "Auto Power Off" under the display, so that might not work. But
it seems to stay turned on when it is measuring something, like a
large electrolytic.

I found it really is necessary to turn it off when moving from one
AC plug to another, otherwise it may give strange results. In fact,
it might be a good idea to post the operating notes found on page 5
of the manual:

Notes on Use

1. This meter is only for indoor use.

2. Turn off the TH2821A while switching the power supply between
battery and DC adapter or replacing the battery.

3. Although internal circuit protection is provided, DC voltage or
current may damage TH2821A. Before you measure a capacitor, be sure
the capacitor is fully discharged.

4. Charging may disturb measurement result sometimes.

5. Nickel Metal Hydride rechargeable battery can be used for the
power supply. TH2821A will not work normally when battery voltage is
less than 6V.

6. The 12V AC to DC adaptor is recommended to be used for TH2821A
power supply.

7. Perform Open and Short corrections for accurate measurement
especially when test fixture is changed.

8. The functions locked with password are not accessible by users.

My biggest problems have been from ignoring rules #2 and #4. I used
to freak out when it didn't do what I thought it should be doing,
but after following the notes, it works fine. And I will add
protection against charged caps, as stated in rule #3. I found that
human error can quickly wipe out a good instrument when you are
working with caps charged to high voltage.

Now I'm wondering if a plain 9V NiCd can be used in place of the
NiMH battery. They are supposed to be interchangeable, but the NiCd
may have a capacity of 120mAh, where the NiMh has 200mAh. So it may
last 3 hours on NiCd, and 5 hours on NiMh. The difference is not
significant for me.

But the NiCd has a much lower discharge rate, so you wouldn't be
running into the issue of leaving it on the shelf for a month, then
trying to use it when the battery is completely discharged. I'm
tempted to get a 9V NiCd and see how it works. If it solves the
self-discharge problem, that's the way to go.

So now I'm happy with the stability of the meter readings on a
quality capacitor, and I won't worry about fluctuation on
electrolytics.

But I'm very unhappy with the self-discharge of NiMh. That may be
solved by switching to a plain NiCd, so it is more likely to have
plenty of charge remaining when I want to use it for some quick
measurements. Afterwards, I can just leave it plugged in and turned
on to bring the battery back up.

I think that covers the issues up to now on this instrument. It is
still by far the best bargain for LCR measurements I have found
anywhere.

Mike

[John S]

On 1/14/2012 3:49 PM, Mike wrote:
> Mike<sp...@me.not> wrote:
>
> > If you want to find bad electrolytics, I don't think you can find
> > a better bargain. It gives the dissipation of the capacitor, so
> > you don't have to fool with lookup tables like you do with a
> > conventional ESR meter to see if the cap is good or bad. Besides
> > giving an easy way to check electrolytics, it also gives the
> > capacitance value to four digits.
>
> Update : it actually displays 4 digits plus a decimal on large
> electrolytics. But the two least significant digits dance around a
> lot.

Try different frequency settings if you have not already

> I switched to a 10uF 250VAC +/-5% film capacitor, and it read
> 10.045uF with the last digit fluctuating between 4 and 6. So I
> conclude electrolytics are not very stable. But the readings are
> quite consistent on a quality part.

Are you kidding? Fluctuations of several millifarads out of 10 uF is a
dream come true for me.

I just charged mine from a lab supply and found it to respond as before,
that is, about 3.7 mA in an OFF condition and about 145 mA in an ON
condition. It was at about 1 bar of the battery indicator on the display
when I started. About an hour later the current dropped to 45 mA as
before and the display indicated 3 bars.

I do not seem to have a problem with self-discharge. I'm wondering
what's going on. Maybe I should open mine to see if the battery is like
yours. Maybe you should contact them with your situation and ask for
assistance.

Also, I've learned not to trust inductance measurements of a 60 Hz
transformer even at 100 Hz. Maybe because it is seeing lots of leakage
inductance or iron loss or something.

I agree that it is a great bargain. We just need to learn about its
limitations. However, your battery problem bugs me. Do you suppose it is
not turning off with the power button?

John

[Mike]

John S <Sop...@invalid.org> wrote:

> On 1/14/2012 3:49 PM, Mike wrote:

>> Mike<sp...@me.not> wrote:

>> Update : it actually displays 4 digits plus a decimal on large
>> electrolytics. But the two least significant digits dance around
>> a lot.

> Try different frequency settings if you have not already

Yes, that seems to have little effect on the electrolytics.

>> I switched to a 10uF 250VAC +/-5% film capacitor, and it read
>> 10.045uF with the last digit fluctuating between 4 and 6. So I
>> conclude electrolytics are not very stable. But the readings are
>> quite consistent on a quality part.

> Are you kidding? Fluctuations of several millifarads out of 10 uF
> is a dream come true for me.

I think you meant fluctuations of several nF. Yes, it has drifted up
to 10.048uF, and is bouncing around between 10.047uF and 10.049uF.

But it spends most of its time on 10.048uF.

I tried to take a picture to show you,but ironically the LiIon
battery in my camera is dead so I have to wait to charge it back up.

I'll post pictures of the display and the capacitor tomorrow. I
expect the reading will change a little, but that's jut normal
drift. Not to worry.

[...]

> I just charged mine from a lab supply and found it to respond as
> before, that is, about 3.7 mA in an OFF condition and about 145 mA
> in an ON condition. It was at about 1 bar of the battery indicator
> on the display when I started. About an hour later the current
> dropped to 45 mA as before and the display indicated 3 bars.

> I do not seem to have a problem with self-discharge. I'm wondering
> what's going on. Maybe I should open mine to see if the battery is
> like yours. Maybe you should contact them with your situation and
> ask for assistance.

I charged mine fully then plugged in but left it turned off for
about a week. When I moved it to a different outlet and turned it
on, the battery indicator showed only one bar.

Either the battery status indicator is not accurate, or the NiMh has
a serious self-discharge. I think it's the NiMh.

> Also, I've learned not to trust inductance measurements of a 60 Hz
> transformer even at 100 Hz. Maybe because it is seeing lots of
> leakage inductance or iron loss or something.

I didn't find any problems on the inductors. I'll check more later.

> I agree that it is a great bargain. We just need to learn about
> its limitations. However, your battery problem bugs me. Do you
> suppose it is not turning off with the power button?

Could be. The operating notes specifically mention turning the unit
off while moving to a different outlet. I did that. The battery did
not last long.

But all the references I can find say the same thing. NiMh has a
high self-discharge. I'll try a NiCd - that should work a lot
better.

I have a bunch of NiCds that I got on sale at RS some time ago. They
sat in my battery box for years without any care or attention. I
discovered a battery charger at a dollar store. I measured the
batteries and they all had some charge remaining even though I never
charged them when I bought them. I charged them and they all came up
with no problems.

So I'm leaning to switch to a 9V NiCd and stop this hassle with NiMh
self-discharge.

> John

Mike

[josephkk]

Thanks, the third one did it for me. I guess i will finally have to
reconsider dealing with ePrey.

?-)

[Mike]

josephkk <joseph_...@sbcglobal.net> wrote:

> Thanks, the third one did it for me. I guess i will finally have to
> reconsider dealing with ePrey.
>
> ?-)

That's great, Joseph. I had a lot of problems with eBay when I first
started using them, but that was many years ago. Since then, it has
turned into a very smooth operation and I've had zero problems. I've only
lost one shipment, and the vendor quickly sent another unit.

One thing I stronly recommend is to split your operating system into
separate installations. One for normal browsing, and a second
installation that is strictly for financial transactions.

I use Ubuntu 10.04 LTS as the host, and VirtualBox as the VM. I have
separate installations of WinXP that provide the services needed for
browsing, banking, software development, etc. I do pcb layout and routing
in Ubuntu so a windows crash will not interrupt an autoroute in progress.

The XP installations are stripped to the bare minimum that is needed for
the required services. That means all unnecessary functions and services
are stripped or disabled. I turn off Auto Update, Restore, Firewall (not
needed), and I don't bother with antivirus programs. Everything else is
turned off and any unnecessary files are deleted.

This allows making a very small installation that is easy to back up to a
spare hard disk. I use a 10GB dynamic hard disk in VBox. The banking file
is only 830MB, and the other installations may be 2GB or so. These copy
very fast to the backup drive, so it is convenient to keep the backups
current. I can increase the size if needed, and shrink it later when the
requirements change.

Then if a virus strikes, or I get a bad software installation that wrecks
the registry, I don't have to reinstall XP and all my files, then try to
get all the original settings back. That takes a very long time and I
never get tham all.

I just copy the backup over the bad file and I am back on the air in a
matter of seconds. The other advantage is I can copy the installation to
a different computer and get a byte-identical installation on the other
computer. XP doesn't know that it is a completely different motherboard
and hard drive, so it doesn't care.

I use the System File Checker from Win98 to check for missing or
corrupted files, and to see if any new ones have suddenly appeared. This
only works with the Win98 version - the XP version does not allow you to
specify the file extensions and folders you want to monitor. It also
eliminates Win7 since that has folders that will not allow Win98 to
enter.

I use the various rootkit detectors to look for keyloggers and other
malware. But the combination of Win98 SFC and Rootkit Revealer pretty
much covers any trojan or virus that can attack the system, so there is
no need to waste time on Symantec or other resource hogs.

The banking installation is the only place where the passwords and logon
information to Paypal and the banks is kept. This information is stored
in Stickey Password manager and is heavily encrypted. So it is not
available to viruses or trojans that may scan the hard disk looking for
text strings. But there is little chance they could be on the banking
computer since it never goes anywhere else except to the financial sites.

If one of the other installations got infected, there is no way the
malware could detect if there is another installation, and none of the
keystrokes on the banking computer can be detected on the other
installations, so a software keylogger will fail.

The banking computer has no access to email, so a phishing attack on the
another computer will fail.

Most of the well-written malware that is aimed at stealing your banking
logon information will shut down as soon as they detect they are running
in a virtual computer. Virtual installations are used in honeypots to try
to find the command servers and lead back to the authors. To protect
themselves, they simply shut down and no longer present any danger. So
using a virtual installation gives added protection against the most
dangerous malware.

Finally, there are two things you can do to vastly increase your
protection against online theft. First, open another account at your
bank. When you do this, it will have the same profile as your current
accounts, and will have the same access rights on a ATM or online. But
have the bank add a block to the account, so the only way you can
transfer money in or out is by visiting the bank in person and having a
manager override the block.

Now you can put most of your money in the account except for what is
needed for miscellaneous purchases. This will keep the majority of your
funds out of the hands of criminals who would otherwise send it to Russia
with love.

The second trick is to change all the answers to the security questions
that the bank asks when you set up your online account, such as "What is
your favorite color", or "What city were you born in."

Instead of answering these questions with the correct information, give
completely nonsense answers such as "!My.Dog.Hass.3.Flees$"

Note the misspelling and punctuation between words. This prevents any
phrase search from finding the string.

This is simple enough that you do not have to write it down, so it will
not be detected by malware that scans the hard disk looking for text
strings.

Use the same answer for all the questions.

Most banks store the browser string from your computer and ask one of the
security questions if they detect a change.

Now, if a criminal somehow manages to get your logon information, they
will probably be logging on from a different computer and will trigger
the security question. But they will not be able to answer it and the
attack will fail.

There are many other attacks that can get through all these protections,
so you always have to be vigilant and keep monitoring your accounts for
unwanted transactions.

But these methods will give a vastly improved security over what you now
have.

Mike

[Mike]

Mike <sp...@me.not> wrote:

> John S <Sop...@invalid.org> wrote:

[...]

>>> I switched to a 10uF 250VAC +/-5% film capacitor, and it read
>>> 10.045uF with the last digit fluctuating between 4 and 6. So I
>>> conclude electrolytics are not very stable. But the readings are
>>> quite consistent on a quality part.

>> Are you kidding? Fluctuations of several millifarads out of 10 uF
>> is a dream come true for me.

> I think you meant fluctuations of several nF. Yes, it has drifted
> up to 10.048uF, and is bouncing around between 10.047uF and
> 10.049uF.

> But it spends most of its time on 10.048uF.

> I tried to take a picture to show you,but ironically the LiIon
> battery in my camera is dead so I have to wait to charge it back
> up.

> I'll post pictures of the display and the capacitor tomorrow. I
> expect the reading will change a little, but that's jut normal
> drift. Not to worry.

OK, here's the original reading on Saturday, Jan 14 2002 at 19:11.
It went up to 10.049uF when I took the picture:

http://static.panoramio.com/photos/original/65001189.jpg

Two days later, on Jan 16 2002, at 06:13, it measured 10.045uF with
the last digit flickering from 4 to 6. Here it is at 5:

http://static.panoramio.com/photos/original/65001190.jpg

I tried to get a picture showing the reading at 10.046uF, but the
best I could do is showing it switching from 6 back to 5:

http://static.panoramio.com/photos/original/65001194.jpg

Another attempt to get it to show 6, but it doesn't stay long
enough. It switches back to 5 as soon as I press the shutter:

http://static.panoramio.com/photos/original/65001199.jpg

Occasionally, it may hit 10.044uF, but I'd have to take a movie to
show it. That would eat up a huge amount of disk space.

So I'm quite happy with the stability on a quality component. Here's
a picture of the capacitor:

http://static.panoramio.com/photos/original/65001201.jpg

I got very similar results on a 25 ohm, 2,000 watt resistor. The
reading was quite stable, with the last digit flickering +/- 1.

I should note that a dmm that can measure a resistor to 5 decimal
places costs a lot more than the Tonghui.

I think it's a fine instrument and can give an honest 5-digits of
resolution. If you see a lot of variation in the readings, I'd check
for a poor connection or try a better component.

Mike

[Mike]

Mike <sp...@me.not> wrote:

[...]

> I got very similar results on a 25 ohm, 2,000 watt resistor. The
> reading was quite stable, with the last digit flickering +/- 1.

I now see the value of an internal battery. It was a whole lot easier to
take the Tonghui to the resistor than try to move the resistor to the shelf
where the Tonghui was plugged in to the AC adapter.

I can envision lots of situations where the portability would be very
convenient, such as working on transmitters, troubleshooting a problem at a
customer's site, making measurements on a plane or a boat, and so on. The
Tonghui gives the 5 digits of resolution that you normally see on a bench
instrument, but you can hold it in your hand and take it with you.

I'm beginning to like this instrument better the more I use it.

Mike

[josephkk]

On Sun, 15 Jan 2012 19:03:20 GMT, Mike <sp...@me.not> wrote:

>josephkk <joseph_...@sbcglobal.net> wrote:
>
>> Thanks, the third one did it for me. I guess i will finally have to
>> reconsider dealing with ePrey.
>>
>> ?-)
>
>That's great, Joseph. I had a lot of problems with eBay when I first
>started using them, but that was many years ago. Since then, it has
>turned into a very smooth operation and I've had zero problems. I've only
>lost one shipment, and the vendor quickly sent another unit.

I hardly ever get phishing email saying it is from ebay or paypal any
more, i used to get several per day. Nowdays they all say they are from
my ISP.

>
>One thing I stronly recommend is to split your operating system into
>separate installations. One for normal browsing, and a second
>installation that is strictly for financial transactions.
>
>I use Ubuntu 10.04 LTS as the host, and VirtualBox as the VM. I have
>separate installations of WinXP that provide the services needed for
>browsing, banking, software development, etc. I do pcb layout and routing
>in Ubuntu so a windows crash will not interrupt an autoroute in progress.

I like this one, i have been wanting to move my financials to a VM. BTW
what PCB software are you using?

>
>The XP installations are stripped to the bare minimum that is needed for
>the required services. That means all unnecessary functions and services
>are stripped or disabled. I turn off Auto Update, Restore, Firewall (not
>needed), and I don't bother with antivirus programs. Everything else is
>turned off and any unnecessary files are deleted.

I turn off auto update on everything that i can, and a VM is way easy to
restore. Have you been able to tell VBox where to put its virtual
machines (like to a specific volume)?

>
>This allows making a very small installation that is easy to back up to a
>spare hard disk. I use a 10GB dynamic hard disk in VBox. The banking file
>is only 830MB, and the other installations may be 2GB or so. These copy
>very fast to the backup drive, so it is convenient to keep the backups
>current. I can increase the size if needed, and shrink it later when the
>requirements change.
>
>Then if a virus strikes, or I get a bad software installation that wrecks
>the registry, I don't have to reinstall XP and all my files, then try to
>get all the original settings back. That takes a very long time and I
>never get tham all.
>
>I just copy the backup over the bad file and I am back on the air in a
>matter of seconds. The other advantage is I can copy the installation to
>a different computer and get a byte-identical installation on the other
>computer. XP doesn't know that it is a completely different motherboard
>and hard drive, so it doesn't care.

I have this one figured out already.

>
>I use the System File Checker from Win98 to check for missing or
>corrupted files, and to see if any new ones have suddenly appeared. This
>only works with the Win98 version - the XP version does not allow you to
>specify the file extensions and folders you want to monitor. It also
>eliminates Win7 since that has folders that will not allow Win98 to
>enter.
>
>I use the various rootkit detectors to look for keyloggers and other
>malware. But the combination of Win98 SFC and Rootkit Revealer pretty
>much covers any trojan or virus that can attack the system, so there is
>no need to waste time on Symantec or other resource hogs.

The use of W98 SFC on XP is a new twist for me.

>
>The banking installation is the only place where the passwords and logon
>information to Paypal and the banks is kept. This information is stored
>in Stickey Password manager and is heavily encrypted. So it is not
>available to viruses or trojans that may scan the hard disk looking for
>text strings. But there is little chance they could be on the banking
>computer since it never goes anywhere else except to the financial sites.

Cool. Not quite there yet. Still learning to get VMs to do just what i
want.

>
>If one of the other installations got infected, there is no way the
>malware could detect if there is another installation, and none of the
>keystrokes on the banking computer can be detected on the other
>installations, so a software keylogger will fail.
>
>The banking computer has no access to email, so a phishing attack on the
>another computer will fail.

Yep.

>
>Most of the well-written malware that is aimed at stealing your banking
>logon information will shut down as soon as they detect they are running
>in a virtual computer. Virtual installations are used in honeypots to try
>to find the command servers and lead back to the authors. To protect
>themselves, they simply shut down and no longer present any danger. So
>using a virtual installation gives added protection against the most
>dangerous malware.
>
>Finally, there are two things you can do to vastly increase your
>protection against online theft. First, open another account at your
>bank. When you do this, it will have the same profile as your current
>accounts, and will have the same access rights on a ATM or online. But
>have the bank add a block to the account, so the only way you can
>transfer money in or out is by visiting the bank in person and having a
>manager override the block.
>
>Now you can put most of your money in the account except for what is
>needed for miscellaneous purchases. This will keep the majority of your
>funds out of the hands of criminals who would otherwise send it to Russia
>with love.

I understand the technique, now i have to reorganize things to make it
work for me.

>
>The second trick is to change all the answers to the security questions
>that the bank asks when you set up your online account, such as "What is
>your favorite color", or "What city were you born in."
>
>Instead of answering these questions with the correct information, give
>completely nonsense answers such as "!My.Dog.Hass.3.Flees$"
>
>Note the misspelling and punctuation between words. This prevents any
>phrase search from finding the string.
>
>This is simple enough that you do not have to write it down, so it will
>not be detected by malware that scans the hard disk looking for text
>strings.

I do a junior grade of this already.

>
>Use the same answer for all the questions.
>
>Most banks store the browser string from your computer and ask one of the
>security questions if they detect a change.
>
>Now, if a criminal somehow manages to get your logon information, they
>will probably be logging on from a different computer and will trigger
>the security question. But they will not be able to answer it and the
>attack will fail.
>
>There are many other attacks that can get through all these protections,
>so you always have to be vigilant and keep monitoring your accounts for
>unwanted transactions.
>
>But these methods will give a vastly improved security over what you now
>have.

Except as noted, i do much of this already.
>
>Mike

[John S]

On 1/16/2012 4:59 AM, Mike wrote:

> I think it's a fine instrument and can give an honest 5-digits of
> resolution. If you see a lot of variation in the readings, I'd check
> for a poor connection or try a better component.
>
> Mike

Agreed.

I found one cause of flickering. Getting within a couple of inches of my
monitor does it. The display was still readable but flickering in the
last two or three digits. If I move the meter a foot or so away, it
stops flickering.

The manual mentions something about using it in a relatively quiet
environment.

John S

[Mike]

josephkk <joseph_...@sbcglobal.net> wrote:

> On Sun, 15 Jan 2012 19:03:20 GMT, Mike <sp...@me.not> wrote:

>> josephkk <joseph_...@sbcglobal.net> wrote:

[...]

> I hardly ever get phishing email saying it is from ebay or paypal

> any more, I used to get several per day. Nowdays they all say they
> are from my ISP.

All you need is one that downloads a keylogger. That can come from
anywhere.

One thing is to use Gishpuppy for disposable emails. It works great
in Firefox, and you can have an unlimited number of email addresses.

>> One thing I strongly recommend is to split your operating system

>> into separate installations. One for normal browsing, and a
>> second installation that is strictly for financial transactions.

>> I use Ubuntu 10.04 LTS as the host, and VirtualBox as the VM. I
>> have separate installations of WinXP that provide the services
>> needed for browsing, banking, software development, etc. I do pcb
>> layout and routing in Ubuntu so a windows crash will not
>> interrupt an autoroute in progress.

> I like this one, I have been wanting to move my financials to a

> VM. BTW what PCB software are you using?

I was using PCAD but it has outlived its usefulness. However, it had
macros, which means you can do wonderful things with your own code.

For example, I could overlay a previous layout on the current pcb
and show exactly where the design had changed. I also made my own
parts selection menu that held my complete inventory, plus automatic
links to datasheets and any other useful information.

I'm looking at Eagle since I understand it also has macros. I'm
hoping to re-use most of the code and simply convert the commands to
the new syntax.

>> The XP installations are stripped to the bare minimum that is
>> needed for the required services. That means all unnecessary
>> functions and services are stripped or disabled. I turn off Auto
>> Update, Restore, Firewall (not needed), and I don't bother with
>> antivirus programs. Everything else is turned off and any
>> unnecessary files are deleted.

> I turn off auto update on everything that I can, and a VM is way

> easy to restore. Have you been able to tell VBox where to put its
> virtual machines (like to a specific volume)?

Do you mean to run the vm on a flash drive? No, I'm not good enough
to figure out how to do that, but my experience with Ubuntu says it
should be possible to do pretty much anything you want. All you have
to do is find someone who has done it and posted the procedure.

One thing I forgot to mention is to turn off the Windows cache. This
simply wastes disk space and has no benefit.

Another thing I should mention is when you are generating the vm,
don't use the latest release of VirtualBox. It will put the vdi file
in its own folder and separated from the other vms, which makes it
difficult to back up.

Instead, use version 3.2.12 to install the vm. This will put all
your vdi files in a single directory where it is easy to pick which
ones you need to back up and do them all at the same time.

However, version 3.2.12 takes forever to boot the vm, so you want to
go to a later version which fixes the slow bootup.

However, don't use the latest release to run the vm. This has
another annoying bug.

VBox added support for Windows Aero starting in version 4.1. Here's
the release note:

"July 19, 2011. Oracle today released VirtualBox 4.1, a new major
release. Introducing VM clones, increased capability for very large
hosts, and Windows Aero support."

This causes the probe in LTspice to align the tail to the wire
instead of the pointer. The problem is described in the LTspice
forum

http://tech.groups.yahoo.com/group/LTspice/message/53351

I found that all the version 4.1.XX releases do the same thing. But
if you go back to version 4.0.12, it fixes the problem. This is the
last version that does not have Aero support, and was released 4
days before. Here's the release note:

"July 15, 2011. Oracle today released VirtualBox 4.0.12, a
maintenance release of VirtualBox 4.0. It improves stability and
fixes regressions."

https://www.virtualbox.org/wiki/News

Also remember to update the Guest Additions when you run 4.0.12.

[...]

>> I use the System File Checker from Win98 to check for missing or
>> corrupted files, and to see if any new ones have suddenly
>> appeared. This only works with the Win98 version - the XP version
>> does not allow you to specify the file extensions and folders you
>> want to monitor. It also eliminates Win7 since that has folders
>> that will not allow Win98 to enter.

>> I use the various rootkit detectors to look for keyloggers and
>> other malware. But the combination of Win98 SFC and Rootkit
>> Revealer pretty much covers any trojan or virus that can attack
>> the system, so there is no need to waste time on Symantec or
>> other resource hogs.

> The use of W98 SFC on XP is a new twist for me.

It is available online. If you can't find it, I will dig up the url.

It is a marvellous little program that can detect a single bit
change in any file. So you can see if a virus has changed any of the
Windows system files or downloaded other files that you don't know
about.

The malware can change the operating system to make the changes
transparent. But if it does this, Rootkit Revealer will show the
infection.

So you get them coming and going. If they don't mask themself, Win98
SFC will catch them. If they do mask themself, Rootkit Revealer will
find them.

>> The banking installation is the only place where the passwords
>> and logon information to Paypal and the banks is kept. This
>> information is stored in Stickey Password manager and is heavily
>> encrypted. So it is not available to viruses or trojans that may
>> scan the hard disk looking for text strings. But there is little
>> chance they could be on the banking computer since it never goes
>> anywhere else except to the financial sites.

> Cool. Not quite there yet. Still learning to get VMs to do just

> what I want.

If you figure out any useful tricks, please post!!!

[...]

>> There are many other attacks that can get through all these
>> protections, so you always have to be vigilant and keep
>> monitoring your accounts for unwanted transactions.

>> But these methods will give a vastly improved security over what
>> you now have.

> Except as noted, I do much of this already.

>>Mike

I think these methods will block most malware attacks. It used to
worry me a great deal that I would lose everything in my bank
account and credit cards, since there is almost no way to avoid
doing financial transactions online.

But now that I have blocked the bank accounts and split the vms, I
can do all my banking and Paypal transactions and I am now free of
the worries that some rootkit or trojan can get to the account.

I also use many other methods, such as Proxomitron to filter
IFRAMES, Drop My Rights to prevent Firefox from installing files in
critical system folders, QuickJava for quick enable and disable of
Java, Javascript, Flash, Silverlight, Images, Stylesheets and Proxy
from the Statusbar, and so on.

I used to use Certificate Patrol to check for changes in the SSL
certificate which would indicate a malware had changed the dns to
point to a copy of the banking site. But it turns out that banks may
change their certificate often enough that it just became a pain to
try to keep track.

Finally, the Win98 SFC method won't work on Win7, so I am committed
to XP for the forseeable future. But I have no interest in Win7. The
basic install requires 6GB since they have included every possible
variation of every DLL they have ever released, and put it all in
the WINSXS folder. So there is no way to get rid of the unwanted
junk that you will probably never use, and the vdi now takes a very
long time to back up. Typical Microsoft crap.

I'm happy with XP. It works fine, and I don't need the fancy
resource hogging features in Win7 and later releases.

Thanks,

Mike

[Mike]

That's very interesting! Thanks. That means to be careful of switching
power supplies and SCR dimmers.

Are you using a CRT or LCD monitor?

Mike

[John S]

LCD.

Hmm... I just repeated the experiment and I don't see much change. I'll
have to be more careful about my observations in the future.

Sorry!

John S

[Mike]

John S <Sop...@invalid.org> wrote:

> On 1/16/2012 12:03 PM, Mike wrote:

[...]

>> That's very interesting! Thanks. That means to be careful of switching
>> power supplies and SCR dimmers.
>>
>> Are you using a CRT or LCD monitor?
>>
>> Mike
>
> LCD.
>
> Hmm... I just repeated the experiment and I don't see much change. I'll
> have to be more careful about my observations in the future.
>
> Sorry!
>
> John S

Don't be sorry. You saw the readings fluctuate. That's exactly the kind
of thing we are looking for. Some erratic performance, or a funny glitch,
or strange behavior. I did the same thing when I first got the unit and
tried to figure out how to get it to work with a dead battery. My
observations and conclusions were way off the mark.

Now I wonder if perhaps the Kelvin clips weren't making good contact, and
moving the unit away from the monitor broke through the oxides and
allowed better contact?

5 digits is 10 to 100 ppm. Things have to be pretty stable to get
reliable readings at that level.

I think maybe we are used to 3 1/2 or 4 digit dmms. So we are not
sensitive to making measurements with a 5 digit resolution, especially on
components that have been sitting in a junkbox for several years.

So far all the quirks have turned out to be violations of the operating
notes, poor quality electrolytics, or perhaps poor contact on the
connections. But we need to find these things and list them so we can get
the best performance from the unit.

So don't be afraid to post any anomalies that occur. I think it was Bob
Pease who made sure his support personnel understood the need to question
any strange behavior in the circuits. Good advice.

Thanks,

Mike

[John S]

All excellent points. But, I need to verify my observations before posting.

If you have a 60Hz transformer around and you have some time, please
make some measurements on its primary. I'm finding that a couple I have
are showing in the half-henry range, yet current/voltage measurements on
the line are showing about 10 times higher. I'm wondering how to track
down the discrepancy.

Thanks,
John S

[Mike]

John S <Sop...@invalid.org> wrote:

> All excellent points. But, I need to verify my observations before
> posting.

I'd still be interested in any quirks you find. These may occur only
rarely, and be so fleeting that it's hard to figure out what is
happening. But if we can collect enough observations, maybe we can pin it
down to something that is easy to prevent.

> If you have a 60Hz transformer around and you have some time, please
> make some measurements on its primary. I'm finding that a couple I
> have are showing in the half-henry range, yet current/voltage
> measurements on the line are showing about 10 times higher. I'm
> wondering how to track down the discrepancy.

I'm not sure what you mean. Is the unloaded current much higher when you
apply 120VAC than the inductance measurement says it should be?

I wonder if there's an issue with waveform distortion or some other
problem with the current meter. Most handhelds do not measure true rms,
so if the transformer is saturating or there is distortion in the line
waveform, they may not give a correct reading.

But I am interested in following up. I just bought two handheld current
clampmeters on eBay, and I made a simple junction box with a small
resistor in the neutral lead so I can look at the current waveform. So
let me know more about the problem and I'll be happy to take a look.

> Thanks,
> John S

Mike

[John S]

On 1/16/2012 1:45 PM, Mike wrote:
> John S<Sop...@invalid.org> wrote:
>
>> All excellent points. But, I need to verify my observations before
>> posting.
>
> I'd still be interested in any quirks you find. These may occur only
> rarely, and be so fleeting that it's hard to figure out what is
> happening. But if we can collect enough observations, maybe we can pin it
> down to something that is easy to prevent.

Repeating some of my recent tests:

I have a 380pF variable cap. When I measured it this time, I got
fluctuations of 1pF on the 100Hz and 120Hz ranges, .2pF excursions on
the 1kHz range, and no change at all on the 10kHz range.

Then I turned on the fluorescent desk lamp about a foot above the
measurement area. I got at least 4pF excursions at 100Hz, 4pF excursions
at 120Hz, 1pF excursions at 1kHz and .2pF excursions at 10kHz.

It appears that the proper frequency range is called for to begin with.
Not a big surprise, I guess, considering how hard it must be to measure
300pF at 100Hz. Not bad, huh?

>> If you have a 60Hz transformer around and you have some time, please
>> make some measurements on its primary. I'm finding that a couple I
>> have are showing in the half-henry range, yet current/voltage
>> measurements on the line are showing about 10 times higher. I'm
>> wondering how to track down the discrepancy.
>
> I'm not sure what you mean. Is the unloaded current much higher when you
> apply 120VAC than the inductance measurement says it should be?

No. If I measure the primary inductance on the Tonghui (at 100Hz), I get
about 535mH and Q of 10. That would calculate out to about 600ma of
unloaded (magnetizing) current at 124VAC, 60 Hz. If I then apply 124AC
at 60Hz to the primary and measure the current, I get .078mA. This
calculates out to about 4H. I'd like to learn why there is so much
discrepancy.

> I wonder if there's an issue with waveform distortion or some other
> problem with the current meter. Most handhelds do not measure true rms,
> so if the transformer is saturating or there is distortion in the line
> waveform, they may not give a correct reading.

I just verified the current at .078mA using an HP 3456A which promises
true RMS. Actually, transformers don't saturate on RMS, but do so on
volt-seconds (forgive me for this slight backslide into pedantry).
However, the V-T to RMS ratio would have to be extraordinary to make a
difference.

> But I am interested in following up. I just bought two handheld current
> clampmeters on eBay, and I made a simple junction box with a small
> resistor in the neutral lead so I can look at the current waveform. So
> let me know more about the problem and I'll be happy to take a look.
>
>> Thanks,
>> John S
>
> Mike

Any info on this I can get would be very much appreciated. I don't like
measurements on things that don't agree, at least by this much.

No hurry. Your job and personal life come first.

Cheers,
John S

[John S]

On 1/16/2012 3:21 PM, John S wrote:

> at 60Hz to the primary and measure the current, I get .078mA.

Aargh! Make that .078A or 78mA. Sorry!

[Mike]

John S <Sop...@invalid.org> wrote:

[...]

> Repeating some of my recent tests:

> I have a 380pF variable cap. When I measured it this time, I got

> fluctuations of 1pF on the 100Hz and 120Hz ranges, 0.2pF

> excursions on the 1kHz range, and no change at all on the 10kHz
> range.

> Then I turned on the fluorescent desk lamp about a foot above the
> measurement area. I got at least 4pF excursions at 100Hz, 4pF

> excursions at 120Hz, 1pF excursions at 1kHz and 0.2pF excursions

> at 10kHz.

> It appears that the proper frequency range is called for to begin
> with. Not a big surprise, I guess, considering how hard it must be
> to measure 300pF at 100Hz. Not bad, huh?

Actually that's pretty good.

I have an office flourescent with two large tubes mounted in the
ceiling about 3 ft above the shelf the Tonghui is on. It doesn't
seem to have affected the readings on the 10uF cap, but I'll run a
test to make sure.

I'll also try to find a variable cap in your range and see if I can
duplicate your results. I also have a smaller desk flourescent lamp
that I can move much closer.

The leads to the Kelvin clips are shielded, but it would be nice to
know if there's any leakage.

I'm quite interested in this topic - any sensitivity to noise could
have undesired results. Thanks for the headsup.

[...]

> No. If I measure the primary inductance on the Tonghui (at 100Hz),
> I get about 535mH and Q of 10. That would calculate out to about
> 600ma of unloaded (magnetizing) current at 124VAC, 60 Hz. If I
> then apply 124AC at 60Hz to the primary and measure the current, I

> get 0.078mA.

> This calculates out to about 4H. I'd like to learn why there is so
> much discrepancy.

OK, I was thinking the discrepancy went the other direction. That is
a curious effect. I have lots of loose transformers. I'll check a
couple and see if I get similar results.

> I just verified the current at 0.078mA using an HP 3456A which

> promises true RMS. Actually, transformers don't saturate on RMS,
> but do so on volt-seconds (forgive me for this slight backslide
> into pedantry).

> However, the V-T to RMS ratio would have to be extraordinary to
> make a difference.

> Any info on this I can get would be very much appreciated. I don't
> like measurements on things that don't agree, at least by this
> much.

> No hurry. Your job and personal life come first.

Aren't you thoughtful!

It's interesting and well worth pursuing. I'll try some checks when
I'm waiting for some other process to finish.

> Cheers,
> John S

Thanks, John. Very good info.

Mike

[John S]

On 1/16/2012 4:16 PM, Mike wrote:
> John S<Sop...@invalid.org> wrote:

> > It appears that the proper frequency range is called for to begin
> > with. Not a big surprise, I guess, considering how hard it must be
> > to measure 300pF at 100Hz. Not bad, huh?
>
> Actually that's pretty good.

Indeed! No complaints from this end.

> [...]
>
> > No. If I measure the primary inductance on the Tonghui (at 100Hz),
> > I get about 535mH and Q of 10. That would calculate out to about
> > 600ma of unloaded (magnetizing) current at 124VAC, 60 Hz. If I
> > then apply 124AC at 60Hz to the primary and measure the current, I
> > get 0.078mA.
>
> > This calculates out to about 4H. I'd like to learn why there is so
> > much discrepancy.

I've done a couple of investigations since yesterday to try to get to
the bottom of this.

First, I checked my Tonghui data against an old HP4260A Universal
Bridge, bought on eek-Bay and long out of calibration. I can produce the
data if you wish, but the crux of it is that they agree with each other.

Well, I tell myself, the transformer must be producing unexpected data.

First, I checked the Tonghui for output voltage when the transformer was
attached. The lower frequency settings (exclude the 10kHz setting)
produced 98 to 141mV RMS.

I then connected the transformer to an HP audio oscillator set for 60Hz
and an HP3400A RMS meter. The results were not only surprising to me,
but they were good support for the believability of the data produced by
the Tonghui.

E(source) V(L) XL(calc) L(calc)
5 3 450 1.2H
3 1.5 350 .92H
.1 .038 247 .66H

Wow! The inductance goes down as the excitation voltage decreases?

Remember, the Tonghui measured .52H even on the 1kHz setting. That's
plenty good for me.

What this tells me is that I cannot trust *any* RLC meter to give me the
inductance of a 60Hz piece of magnetics at low excitation voltage.

I have a lot more to learn about magnetics. But, the Tonghui is not at
fault and I need more education.

Cheers,
John S

[Mike]

John S <Sop...@invalid.org> wrote:

[...]

> I've done a couple of investigations since yesterday to try to get
> to the bottom of this.

> First, I checked my Tonghui data against an old HP4260A Universal
> Bridge, bought on eek-Bay and long out of calibration. I can
> produce the data if you wish, but the crux of it is that they
> agree with each other.

That's very good news. Thanks for the info.

> Well, I tell myself, the transformer must be producing unexpected
> data.

That was my feeling also. I was concerned there might be a bit of
residual magnetism left after running on 120VAC. I thought that
might bias the transformer partway up the BH curve and give spurious
results.

My plan was to measure with the Tonghui, measure on 120VAC, then
back to the Tonghui again. But too busy at the moment to start it.

> First, I checked the Tonghui for output voltage when the
> transformer was attached. The lower frequency settings (exclude
> the 10kHz setting) produced 98 to 141mV RMS.

Is that measuring the output of the Tonghui across the primary of
the transformer?

> I then connected the transformer to an HP audio oscillator set for
> 60Hz and an HP3400A RMS meter. The results were not only
> surprising to me, but they were good support for the believability
> of the data produced by the Tonghui.

> E(source) V(L) XL(calc) L(calc)
> 5 3 450 1.2H

> 3 1.5 350 0.92H
> 0.1 0.038 247 0.66H

> Wow! The inductance goes down as the excitation voltage decreases?

What is V(L) - the voltage across the primary? Is that using the
ouput impedance of the sig gen in series with the primary? What is
the output impedance of the sig gen, and the resistance of the
primary?

In the old days, we used transformers to couple the output of 50B5's
and 6L6's to speakers. These transformers used laminations very
similar to power transformers. In fact, if you were in a pinch, you
could use a power transformer as the output transformer.

We also used transformers at the input to audio amplifiers to break
common-mode hum problems, such as PA systems and intercoms.

So the transformers had to be pretty linear wrt amplitude, else we
would see plenty of articles in Electronics World about reducing
low-level distortions.

OTOH, today's power transformers may use different steel, which may
have nonlinear characteristics or some residual magnetism.

Recall the power transformer in a microwave oven is running pretty
close to saturation to minimize the amount of iron needed to reduce
cost and weight.

> Remember, the Tonghui measured 0.52H even on the 1kHz setting.

> That's plenty good for me.

> What this tells me is that I cannot trust *any* RLC meter to give
> me the inductance of a 60Hz piece of magnetics at low excitation
> voltage.

This is becoming a very interesting subject. Thanks for bringing it
up and for the good data.

> I have a lot more to learn about magnetics. But, the Tonghui is
> not at fault and I need more education.

I have studiously avoided learning anything about magnetics for over
60 years. But it looks like my golden days of ignorance are about to
come to an end. I had already come to the conclusion it was time to
start learning about magnetics since I need to do some work on pwm
power supplies for a new product. It looks like you have accelerated
the process:)

> Cheers,
> John S

Thanks John. Very interesting info.

Mike

[John S]

On 1/17/2012 3:54 PM, Mike wrote:
> John S<Sop...@invalid.org> wrote:
>
> [...]
>
> > I've done a couple of investigations since yesterday to try to get
> > to the bottom of this.
>
> > First, I checked my Tonghui data against an old HP4260A Universal
> > Bridge, bought on eek-Bay and long out of calibration. I can
> > produce the data if you wish, but the crux of it is that they
> > agree with each other.
>
> That's very good news. Thanks for the info.
>
> > Well, I tell myself, the transformer must be producing unexpected
> > data.
>
> That was my feeling also. I was concerned there might be a bit of
> residual magnetism left after running on 120VAC. I thought that
> might bias the transformer partway up the BH curve and give spurious
> results.
>
> My plan was to measure with the Tonghui, measure on 120VAC, then
> back to the Tonghui again. But too busy at the moment to start it.
>
> > First, I checked the Tonghui for output voltage when the
> > transformer was attached. The lower frequency settings (exclude
> > the 10kHz setting) produced 98 to 141mV RMS.
>
> Is that measuring the output of the Tonghui across the primary of
> the transformer?

Yes.

> > I then connected the transformer to an HP audio oscillator set for
> > 60Hz and an HP3400A RMS meter. The results were not only
> > surprising to me, but they were good support for the believability
> > of the data produced by the Tonghui.
>
> > E(source) V(L) XL(calc) L(calc)
> > 5 3 450 1.2H
> > 3 1.5 350 0.92H
> > 0.1 0.038 247 0.66H
>
> > Wow! The inductance goes down as the excitation voltage decreases?
>
> What is V(L) - the voltage across the primary? Is that using the
> ouput impedance of the sig gen in series with the primary? What is
> the output impedance of the sig gen, and the resistance of the
> primary?

Yes to your first question. Output resistance: 600 ohms. DC primary
resistance: 11.5 ohms.

> In the old days, we used transformers to couple the output of 50B5's
> and 6L6's to speakers. These transformers used laminations very
> similar to power transformers. In fact, if you were in a pinch, you
> could use a power transformer as the output transformer.

Usually, audio used thinner laminations than 60Hz transformers. The lams
could be had much less than .014 inches.

> We also used transformers at the input to audio amplifiers to break
> common-mode hum problems, such as PA systems and intercoms.
>
> So the transformers had to be pretty linear wrt amplitude, else we
> would see plenty of articles in Electronics World about reducing
> low-level distortions.
>
> OTOH, today's power transformers may use different steel, which may
> have nonlinear characteristics or some residual magnetism.
>
> Recall the power transformer in a microwave oven is running pretty
> close to saturation to minimize the amount of iron needed to reduce
> cost and weight.

Yes. I think the lams run about .014 thick.

> > Remember, the Tonghui measured 0.52H even on the 1kHz setting.
>
> > That's plenty good for me.
>
> > What this tells me is that I cannot trust *any* RLC meter to give
> > me the inductance of a 60Hz piece of magnetics at low excitation
> > voltage.
>
> This is becoming a very interesting subject. Thanks for bringing it
> up and for the good data.
>
> > I have a lot more to learn about magnetics. But, the Tonghui is
> > not at fault and I need more education.
>
> I have studiously avoided learning anything about magnetics for over
> 60 years. But it looks like my golden days of ignorance are about to
> come to an end. I had already come to the conclusion it was time to
> start learning about magnetics since I need to do some work on pwm
> power supplies for a new product. It looks like you have accelerated
> the process:)
>
> > Cheers,
> > John S
>
> Thanks John. Very interesting info.
>
> Mike

You're welcome. I think this is now outside the Tonghui subject into the
subject of magnetics. The lesson, though, is don't trust LCR meters with
their low excitation to give valid results on large magnetics.

Cheers,
John S

[Mike]

John S <Sop...@invalid.org> wrote:

> On 1/17/2012 3:54 PM, Mike wrote:

>> John S<Sop...@invalid.org> wrote:

>>> First, I checked the Tonghui for output voltage when the
>>> transformer was attached. The lower frequency settings (exclude
>>> the 10kHz setting) produced 98 to 141mV RMS.

>> Is that measuring the output of the Tonghui across the primary of
>> the transformer?

> Yes.

That's good info. Too low to turn on bipolar junctions.

>>> I then connected the transformer to an HP audio oscillator set
>>> for 60Hz and an HP3400A RMS meter. The results were not only
>>> surprising to me, but they were good support for the
>>> believability of the data produced by the Tonghui.

>>> E(source) V(L) XL(calc) L(calc)
>>> 5 3 450 1.2H
>>> 3 1.5 350 0.92H 0.1 0.038
>>> 247 0.66H

>>> Wow! The inductance goes down as the excitation voltage
>>> decreases?

>> What is V(L) - the voltage across the primary? Is that using the
>> ouput impedance of the sig gen in series with the primary? What
>> is the output impedance of the sig gen, and the resistance of the
>> primary?

> Yes to your first question. Output resistance: 600 ohms. DC
> primary resistance: 11.5 ohms.

Thanks. Primary resistance is not going to have much effect. But
what is the last line showing 247 volts and 0.66H? Is that from the
previous 220VAC measurement? If so where do you live that you have
220VAC in a wall socket?

[...]

>> Thanks John. Very interesting info.

>> Mike

> You're welcome. I think this is now outside the Tonghui subject
> into the subject of magnetics. The lesson, though, is don't trust
> LCR meters with their low excitation to give valid results on
> large magnetics.

It looks like you have opened a Pandora's box issue. We need to
learn more why a low-level measurement doesn't work on laminated
cores. What is the mechanism that is causing the discrepancies? Are
there any web links that discuss this in greater detail? Does the
same thing happen on toroids?

This is a very important subject for the Tonghui. If you want to gap
a core, you need to know the inductance you should get after gapping
to confirm it is correct. If the Tonghui can't measure it, I think
we're in trouble.

[John S]

On 1/17/2012 4:50 PM, Mike wrote:
> John S<Sop...@invalid.org> wrote:
>
> > On 1/17/2012 3:54 PM, Mike wrote:
>
> >> John S<Sop...@invalid.org> wrote:
>
> >>> First, I checked the Tonghui for output voltage when the
> >>> transformer was attached. The lower frequency settings (exclude
> >>> the 10kHz setting) produced 98 to 141mV RMS.
>
> >> Is that measuring the output of the Tonghui across the primary of
> >> the transformer?
>
> > Yes.
>
> That's good info. Too low to turn on bipolar junctions.

The 10kHz setting produced 217mV while attached to the primary. Still
low enough.

Unloaded output from the Tonghui:

Hz Vrms
100 288mV
120 287mV
1k 274mV
10k 133mV

Some loading is to be expected. But, still low enough even at no load. Good!

> >>> I then connected the transformer to an HP audio oscillator set
> >>> for 60Hz and an HP3400A RMS meter. The results were not only
> >>> surprising to me, but they were good support for the
> >>> believability of the data produced by the Tonghui.
>
> >>> E(source) V(L) XL(calc) L(calc)
> >>> 5 3 450 1.2H
> >>> 3 1.5 350 0.92H 0.1 0.038
> >>> 247 0.66H
>

> But
> what is the last line showing 247 volts and 0.66H?

I think it is due to line wrap with all the >'s building up: Original was...

E(source) V(L) XL(calc) L(calc)
5 3 450 1.2H

3 1.5 350 .92H
.1 .038 247 .66H

>

> [...]
>
> >> Thanks John. Very interesting info.
>
> >> Mike
>
> > You're welcome. I think this is now outside the Tonghui subject
> > into the subject of magnetics. The lesson, though, is don't trust
> > LCR meters with their low excitation to give valid results on
> > large magnetics.
>
> It looks like you have opened a Pandora's box issue. We need to
> learn more why a low-level measurement doesn't work on laminated
> cores. What is the mechanism that is causing the discrepancies? Are
> there any web links that discuss this in greater detail? Does the
> same thing happen on toroids?

All good questions. I have my suspicions, but I'll do some research
before I present them.

> This is a very important subject for the Tonghui. If you want to gap
> a core, you need to know the inductance you should get after gapping
> to confirm it is correct. If the Tonghui can't measure it, I think
> we're in trouble.

Well, yes, but not just the Tonghui. This seems to apply to any RLC
instrument that uses low excitation. At least, so it seems for now (Two
in a row). I wouldn't shun further experiments and data.

Thank you,
John S

[amdx]

It's all in the "Slope of the BH curve".
At low currents the slope of the BH curve is more vertical and turns
horizontal at higher current.
See the link,

http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx

Click it, it opens to a pdf, then it is large enough to see the slope of
the initial ramp up, ( the line that starts at 0,0) which is what I
think is similar to the slope at the low currents.
Mikek

[amdx]

>> E(source) V(L) XL(calc) L(calc)
>> 5 3 450 1.2H
>> 3 1.5 350 .92H
>> .1 .038 247 .66H
>>
>> Wow! The inductance goes down as the excitation voltage decreases?
>>
>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>> plenty good for me.
>>
>> What this tells me is that I cannot trust *any* RLC meter to give me the
>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>
>> I have a lot more to learn about magnetics. But, the Tonghui is not at
>> fault and I need more education.
>>
>> Cheers,
>> John S
>
> It's all in the "Slope of the BH curve".
> At low currents the slope of the BH curve is more vertical and turns
> horizontal at higher current.
> See the link,
>
> http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
>
> Click it, it opens to a pdf, then it is large enough to see the slope of
> the initial ramp up, ( the line that starts at 0,0) which is what I
> think is similar to the slope at the low currents.
> Mikek
>
>

Hey, I got the vertical/ horiz reversed in the last post.

Found a couple of better curves.

Oh, this one is good, at least for my explanation.

http://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.html

The graph, note the air line is horizontal (an aircore would have less
inductance)
See the iron line is more vertical, iron will have more inductance than air.
Now if you have low currents the slope is more like air having lower
inductance.



http://kiran111.hubpages.com/hub/CRGO-core-Laminations-Of-Electrical-Transformer

http://vtuphysics.blogspot.com/2008/07/unit-4.html
Mikek

[josephkk]

On Tue, 17 Jan 2012 22:50:42 GMT, Mike <sp...@me.not> wrote:

>
> > You're welcome. I think this is now outside the Tonghui subject
> > into the subject of magnetics. The lesson, though, is don't trust
> > LCR meters with their low excitation to give valid results on
> > large magnetics.

I have seen it before and seen an explanation that seemed reasonable at
the time. I was a LOT better with magnetics back then (25-30 years ago),
but still no great shakes. I think is may be related to effective air gap
due to the laminations meeting up less than perfectly; not that i remember
any such information.

Maybe someone here who does know something about magnetics can help us out
here.

>
> It looks like you have opened a Pandora's box issue. We need to
> learn more why a low-level measurement doesn't work on laminated
> cores. What is the mechanism that is causing the discrepancies? Are
> there any web links that discuss this in greater detail? Does the
> same thing happen on toroids?

Magnetic material is also part of the mess, maybe more important than core
shape. Certainly laminated and tape wound cores may be the most
problematic.

[josephkk]

On Tue, 17 Jan 2012 17:50:47 -0600, amdx <am...@knologynotthis.net> wrote:

>
>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>> plenty good for me.
>>
>> What this tells me is that I cannot trust *any* RLC meter to give me the
>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>
>> I have a lot more to learn about magnetics. But, the Tonghui is not at
>> fault and I need more education.
>>
>> Cheers,
>> John S
>
> It's all in the "Slope of the BH curve".
>At low currents the slope of the BH curve is more vertical and turns
>horizontal at higher current.
> See the link,
>
>http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
>
>Click it, it opens to a pdf, then it is large enough to see the slope of
>the initial ramp up, ( the line that starts at 0,0) which is what I
>think is similar to the slope at the low currents.
> Mikek
>

In the hysteresis curves please not that there is a small low slope part
just coming off 0,0. That is part of where it is coming from.

?-)

[Tim Williams]

"josephkk" <joseph_...@sbcglobal.net> wrote in message
news:ruech7leag4uj6kv3...@4ax.com...
> > <low level inductance>

>
> Maybe someone here who does know something about magnetics can help us
> out here.

Quite simply, magnetic domains are "sticky". Down at low levels, buried
in the hysteresis loop of the material, small-signal loops are flatter
because few domains are responding.

I'm sure this effect has a strong tempco, since higher temperatures free
more domains (much like dithering a balance to get it to the equilibrium
position despite bearing friction). It's present in all metallic
materials I know of, though you'll have a hard time measuring it in
super-high permeability materials due to the extremely small hysteresis
loop, and in powdered materials, since they have a lot of gap in the
matrix already.

Still, powdered materials yield a fair amount of change:
http://www.micrometals.com/materials_index.html
Mix 26 is the familiar yellow/white toroid used in just about every power
supply, quite cheap and lossy, but high permeability (mu = 75).

I'm trying to remember if I've seen an analogous curve for ferrites. If I
have, I don't remember which manufacturer had the curve...

The tempco is more easily observed in ferrites than metals, since the
curie temperature is lower (which is like a magnetic "melting point"; it
loses all order and ceases to be ferro/ferrimagnetic at that temperature).
Permeability almost always rises on approaching the curie point (which, I
suppose, is like water becoming less viscous as it approaches the boiling
point), which means more domains are being more easily moved; meanwhile,
saturation flux goes down, which means fewer and fewer are staying in
their polarized positions. At curie, Bsat suddenly drops to air-cored
levels.

> > This is a very important subject for the Tonghui. If you want to gap
> > a core, you need to know the inductance you should get after gapping
> > to confirm it is correct. If the Tonghui can't measure it, I think
> > we're in trouble.

Well, a gapped core doesn't depend on the core very much, so you're okay
on that one. I'd worry more about the expansion tempco of whatever the
core spacing material is!

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

[amdx]

Sorry, can you rephrase that, I don't understand what you wanted to say.
Mikek

[John S]

Thanks for the links, Mikek, and for your comments, josephkk.

I spent all morning researching the question. The best answer I could
find was here:

http://www.magmet.com/lamination/pdf/Superperm49.pdf

Note that the AC permeability (page 1) increases with increasing flux
density. A crude estimate of the B involved with my measurements gives
about 60 gauss (.1V @ 100Hz) for the Tonghui and about 600 gauss when
the HP audio oscillator was set for 5V.

The AC permeability would therefore go from about 6000 to about 30,000
for about a 5 to 1 increase in inductance. My actual measurements were
about 2 to 1, but, as I said, this is a very crude estimate.

This doesn't answer *why* the permeability changes, but does point out
that the inductance of cored inductors will change with B. So, I think
we can expect usually lower inductance readings from the Tonghui,
especially for the power magnetics cases.

Here is another shot showing powdered iron core changes of inductance
with flux density:

http://www.micrometals.com/material/AC60HzDsgntxt.html

Cheers,
John S

[josephkk]

Tim Williams explained it soo much better. At very low flux levels there
is a lower proportion of domains responding (per Ampere Turn) to the
impressed flux, thus lower effective Mu(r) and lower inductance.

?-)

[Phil Hobbs]

Sort of like a magnetic version of crossover distortion.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[amdx]

That's very good. I have ask a couple of times about this phenomena
and could not generate any interest.
My line of questioning had to do with transformers at the RF input of
a radio. The signal can be as low as 1 uV.(less than a picowatt) I'm
sure when you look at the spec's for *Mu(r) it was measured at much
higher power levels. So the transformers used at these low levels should
have many more turns than the spec's would lead you to believe.
Yet, I have not seen any references to support this.

*Mu(r) I'm assuming this symbol is for initial permeability, I have
not seen it put this way.
Ok, I Googled Mu and got μ.
Ya, I had to copy and paste the symbol.
Thanks, Mikek