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A useful addition to your toolkit
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Cursitor Doom
Mar 5, 2017, 9:50:55 AM3/5/17
to
https://www.sparkfun.com/products/11005
Replace the existing connector with a BNC, add a bit of series resistance
and you have a *very* cheap current probe for your scope.
Replace the existing connector with a BNC, add a bit of series resistance
and you have a *very* cheap current probe for your scope.
John Larkin
Mar 5, 2017, 10:44:24 AM3/5/17
to
indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
aren't terribly interesting.
My real problem with current measurement is DC, on PC boards. We want
to know how much current, say, an FPGA is using. Sometimes I include
current shunts in a layout, but sometimes I don't.
One can use existing switcher inductors as current shunts. I wish I
had a PCB trace current probe, but that's probably not posssible. You
can measure millivolt and microvolt drops across traces and vias.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
Cursitor Doom
Mar 5, 2017, 11:20:53 AM3/5/17
to
On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote:
> I have a clamp-on ammeter that pretty much does that, although it just
> indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
> aren't terribly interesting.
Indeed they're not. But your meter is presumably *only* designed for use
> I have a clamp-on ammeter that pretty much does that, although it just
> indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
> aren't terribly interesting.
at 60Hz, I would imagine. Hook it up to a 100Hz signal and you'll see
nothing at all in all probability. ;-)
> One can use existing switcher inductors as current shunts. I wish I had
> a PCB trace current probe, but that's probably not posssible. You can
> measure millivolt and microvolt drops across traces and vias.
I can justify to splash out on as a mere hobbyist.
John Larkin
Mar 5, 2017, 12:28:51 PM3/5/17
to
makes 25 millivolts, and lots of cheapish DVMs will resolve that well
enough. You probably need a bench DVM with microvolt resolution to
measure, say, 1 amp running through a via, but you could build a
little microvolt meter or amp pretty easily. PCB trace and via
resistances need to be calibrated, which is only a minor nuisance.
Here are some pcb-trace shunts, down near the connector:
https://dl.dropboxusercontent.com/u/53724080/PCBs/TEM2_Power_Board.JPG
One of the great mysteries of electronics is "where is the current
going?" Sometimes a thermal imager helps figure that out. A little
magnetometer would be fun, not hard to do these days.
MJC
Mar 5, 2017, 3:56:51 PM3/5/17
to
In article <fuhobcdhvlfcm9ik7...@4ax.com>,
jjla...@highlandtechnology.com says...
puzzle for all clamp meters... Surely they are no good clamped on a
normal bi-directional power cable in which the current is both coming
and going: the magnetic fields will near-perfectly cancel out. Surely
you have to split the cable to measure current?
Mike.
jjla...@highlandtechnology.com says...
>
> One of the great mysteries of electronics is "where is the current
> going?" Sometimes a thermal imager helps figure that out. A little
> magnetometer would be fun, not hard to do these days.
Reading the blurb on the cited current transformer reminded me of a
> One of the great mysteries of electronics is "where is the current
> going?" Sometimes a thermal imager helps figure that out. A little
> magnetometer would be fun, not hard to do these days.
puzzle for all clamp meters... Surely they are no good clamped on a
normal bi-directional power cable in which the current is both coming
and going: the magnetic fields will near-perfectly cancel out. Surely
you have to split the cable to measure current?
Mike.
Foxs Mercantile
Mar 5, 2017, 4:07:51 PM3/5/17
to
They do make special current probes specifically for doing traces
on a PC board. without cutting traces or requiring a loop of wire.
<http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com
on a PC board. without cutting traces or requiring a loop of wire.
<http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com
John Larkin
Mar 5, 2017, 4:37:42 PM3/5/17
to
On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile <jda...@att.net>
wrote:
>They do make special current probes specifically for doing traces
>on a PC board. without cutting traces or requiring a loop of wire.
><http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
Looks expensive, and I'd guess not very accurate.
wrote:
>They do make special current probes specifically for doing traces
>on a PC board. without cutting traces or requiring a loop of wire.
><http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
Foxs Mercantile
Mar 5, 2017, 6:41:39 PM3/5/17
to
On 3/5/2017 3:37 PM, John Larkin wrote:
> Looks expensive, and I'd guess not very accurate.
<http://www.aimtti.us/product-category/current-probes/aim-i-prober-520>
> Looks expensive, and I'd guess not very accurate.
It is expensive. At $795 for the basic probe.
Data sheet:
<http://resources.aimtti.com/datasheets/prec-iprober520-5p.pdf>
Instruction manual:
<http://resources.aimtti.com/manuals/I-prober_Instruction_Manual-Iss5.pdf>
Winfield Hill
Mar 5, 2017, 7:35:48 PM3/5/17
to
Foxs Mercantile wrote...
give us adequate help in debugging our switching
power supply designs. But the calibrating scheme
for trace current measurements looks iffy. But
maybe along with other measurements, power in,
voltage and power out, etc., it could do the job.
It is fast enough to look at inductor currents.
--
Thanks,
- Win
>
> John Larkin wrote:
>> Looks expensive, and I'd guess not very accurate.
>
><http://www.aimtti.us/product-category/current-probes/aim-i-prober-520>
>It is expensive. At $795 for the basic probe.
>Data sheet:
><http://resources.aimtti.com/datasheets/prec-iprober520-5p.pdf>
>Instruction manual:
><http://resources.aimtti.com/manuals/I-prober_Instruction_Manual-Iss5.pdf>
The expense we can handle, if, for example, it'll
> John Larkin wrote:
>> Looks expensive, and I'd guess not very accurate.
>
><http://www.aimtti.us/product-category/current-probes/aim-i-prober-520>
>It is expensive. At $795 for the basic probe.
>Data sheet:
><http://resources.aimtti.com/datasheets/prec-iprober520-5p.pdf>
>Instruction manual:
><http://resources.aimtti.com/manuals/I-prober_Instruction_Manual-Iss5.pdf>
give us adequate help in debugging our switching
power supply designs. But the calibrating scheme
for trace current measurements looks iffy. But
maybe along with other measurements, power in,
voltage and power out, etc., it could do the job.
It is fast enough to look at inductor currents.
--
Thanks,
- Win
k...@notreal.com
Mar 5, 2017, 7:41:51 PM3/5/17
to
On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin
<jjla...@highlandtechnology.com> wrote:
>On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
><cu...@notformail.com> wrote:
>
>>https://www.sparkfun.com/products/11005
>>
>>Replace the existing connector with a BNC, add a bit of series resistance
>>and you have a *very* cheap current probe for your scope.
>
>I have a clamp-on ammeter that pretty much does that, although it just
>indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
>aren't terribly interesting.
>
>My real problem with current measurement is DC, on PC boards. We want
>to know how much current, say, an FPGA is using. Sometimes I include
>current shunts in a layout, but sometimes I don't.
I generally use a ferrite (pi filter) on the supplies to uCs and DSPs
>On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
><cu...@notformail.com> wrote:
>
>>https://www.sparkfun.com/products/11005
>>
>>Replace the existing connector with a BNC, add a bit of series resistance
>>and you have a *very* cheap current probe for your scope.
>
>I have a clamp-on ammeter that pretty much does that, although it just
>indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
>aren't terribly interesting.
>
>My real problem with current measurement is DC, on PC boards. We want
>to know how much current, say, an FPGA is using. Sometimes I include
>current shunts in a layout, but sometimes I don't.
for EMI, then substitute a shunt to measure the power during test.
>
>One can use existing switcher inductors as current shunts. I wish I
>had a PCB trace current probe, but that's probably not posssible. You
>can measure millivolt and microvolt drops across traces and vias.
The old HP current probe was a great debugging tool.
>One can use existing switcher inductors as current shunts. I wish I
>had a PCB trace current probe, but that's probably not posssible. You
>can measure millivolt and microvolt drops across traces and vias.
Phil Allison
Mar 5, 2017, 8:15:38 PM3/5/17
to
John Larkin wrote:
>
>
> I have a clamp-on ammeter that pretty much does that, although it just
> indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
> aren't terribly interesting.
>
** Mains current waveforms are VERY interesting, but not if all you can see is 60Hz. A Hall effect transducer is needed to do the job properly.
>
>
> I have a clamp-on ammeter that pretty much does that, although it just
> indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
> aren't terribly interesting.
>
The one is use is by LEM and has response to 100kHz, allows me to see currents as low as 1mA and up to 100A peak.
.... Phil
JM
Mar 5, 2017, 9:43:29 PM3/5/17
to
On 05/03/2017 15:44, John Larkin wrote:
> I have a clamp-on ammeter that pretty much does that, although it just
> indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
> aren't terribly interesting.
Tell that to a condition monitoring engineer!
> I have a clamp-on ammeter that pretty much does that, although it just
> indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
> aren't terribly interesting.
John Larkin
Mar 5, 2017, 11:02:23 PM3/5/17
to
On Sun, 05 Mar 2017 19:56:44 +0000, JM <dontreply...@gmail.com>
wrote:
I don't design AC power supplies any more. I can buy an entire nice
PFC switcher for less than I could buy a 60 Hz power transformer.
Since the supplies all come with UL/CE/VDE/etc stickers, I don't care
about their input current waveforms.
wrote:
PFC switcher for less than I could buy a 60 Hz power transformer.
Since the supplies all come with UL/CE/VDE/etc stickers, I don't care
about their input current waveforms.
rickman
Mar 6, 2017, 12:58:30 AM3/6/17
to
On 3/5/2017 4:37 PM, John Larkin wrote:
> On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile <jda...@att.net>
> wrote:
>
>> They do make special current probes specifically for doing traces
>> on a PC board. without cutting traces or requiring a loop of wire.
>> <http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
>
> Looks expensive, and I'd guess not very accurate.
Seems to me it would be a *great* tool for finding where the currents
> On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile <jda...@att.net>
> wrote:
>
>> They do make special current probes specifically for doing traces
>> on a PC board. without cutting traces or requiring a loop of wire.
>> <http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
>
> Looks expensive, and I'd guess not very accurate.
are going. I thought that would be a good thing?
--
Rick C
Foxs Mercantile
Mar 6, 2017, 1:57:06 AM3/6/17
to
On 3/5/2017 11:58 PM, rickman wrote:
>
> Seems to me it would be a *great* tool for finding where the
> currents are going. I thought that would be a good thing?
It is. But some people have difficulty accepting anything more
>
> Seems to me it would be a *great* tool for finding where the
> currents are going. I thought that would be a good thing?
complicated than a light bulb, or more expensive than a pack of
cigarettes.
rickman
Mar 6, 2017, 2:04:24 AM3/6/17
to
On 3/6/2017 1:56 AM, Foxs Mercantile wrote:
> On 3/5/2017 11:58 PM, rickman wrote:
>>
>> Seems to me it would be a *great* tool for finding where the
>> currents are going. I thought that would be a good thing?
>
> It is. But some people have difficulty accepting anything more
> complicated than a light bulb, or more expensive than a pack of
> cigarettes.
You mean like thermal cameras?
> On 3/5/2017 11:58 PM, rickman wrote:
>>
>> Seems to me it would be a *great* tool for finding where the
>> currents are going. I thought that would be a good thing?
>
> It is. But some people have difficulty accepting anything more
> complicated than a light bulb, or more expensive than a pack of
> cigarettes.
--
Rick C
piglet
Mar 6, 2017, 6:01:17 AM3/6/17
to
On 06/03/2017 00:41, k...@notreal.com wrote:
> The old HP current probe was a great debugging tool.
>
+1 I'd love an HP-547A
> The old HP current probe was a great debugging tool.
>
piglet
Cursitor Doom
Mar 6, 2017, 6:30:41 AM3/6/17
to
On Mon, 06 Mar 2017 00:56:56 -0600, Foxs Mercantile wrote:
> It is. But some people have difficulty accepting anything more
> complicated than a light bulb, or more expensive than a pack of
> cigarettes.
For the *real* cheapskates out there, there's this alternative:
> It is. But some people have difficulty accepting anything more
> complicated than a light bulb, or more expensive than a pack of
> cigarettes.
http://www.ebay.com/itm/100A-SCT-013-000-Non-invasive-AC-current-sensor-
Split-Core-Transformer-YH-/201842524936?
hash=item2efec08308:g:vm8AAOSwCGVX3BYF
Claims to be able to handle up to 100A!
John Larkin
Mar 6, 2017, 11:43:28 AM3/6/17
to
On Mon, 6 Mar 2017 00:56:56 -0600, Foxs Mercantile <jda...@att.net>
wrote:
>On 3/5/2017 11:58 PM, rickman wrote:
>>
>> Seems to me it would be a *great* tool for finding where the
>> currents are going. I thought that would be a good thing?
>
>It is. But some people have difficulty accepting anything more
>complicated than a light bulb, or more expensive than a pack of
>cigarettes.
It's not hard to figure where current is going: just measure voltage
drops. What's sometimes difficult is quantifying it.
Just now we're laying out a 10-layer board with two ground planes and
three power planes. There are 22 power supplies. Most of the power
distribution will be interestingly-shaped interleaved pours, not
traces, on various layers.
That magnetic gadget would be hopelessly confused. Multiple currents
and various return paths would make it useless.
My favorite tool for tracing unusual current flows is my Flir E45
thermal imager. It cost $12,000.
We just demoed a cool new thermal imager, mounted on a nice little
stand, with its own display and also USB interfaced for pics or
movies. They're going to let us keep it.
wrote:
>On 3/5/2017 11:58 PM, rickman wrote:
>>
>> Seems to me it would be a *great* tool for finding where the
>> currents are going. I thought that would be a good thing?
>
>It is. But some people have difficulty accepting anything more
>complicated than a light bulb, or more expensive than a pack of
>cigarettes.
drops. What's sometimes difficult is quantifying it.
Just now we're laying out a 10-layer board with two ground planes and
three power planes. There are 22 power supplies. Most of the power
distribution will be interestingly-shaped interleaved pours, not
traces, on various layers.
That magnetic gadget would be hopelessly confused. Multiple currents
and various return paths would make it useless.
My favorite tool for tracing unusual current flows is my Flir E45
thermal imager. It cost $12,000.
We just demoed a cool new thermal imager, mounted on a nice little
stand, with its own display and also USB interfaced for pics or
movies. They're going to let us keep it.
Michael A. Terrell
Mar 6, 2017, 8:56:12 PM3/6/17
to
Cursitor Doom wrote:
> On Mon, 06 Mar 2017 00:56:56 -0600, Foxs Mercantile wrote:
>
>> It is. But some people have difficulty accepting anything more
>> complicated than a light bulb, or more expensive than a pack of
>> cigarettes.
>
> For the *real* cheapskates out there, there's this alternative:
>
> http://www.ebay.com/itm/201842524936
> On Mon, 06 Mar 2017 00:56:56 -0600, Foxs Mercantile wrote:
>
>> It is. But some people have difficulty accepting anything more
>> complicated than a light bulb, or more expensive than a pack of
>> cigarettes.
>
> For the *real* cheapskates out there, there's this alternative:
>
>
> Claims to be able to handle up to 100A!
Let's see you use it to find a stray 100 mA DC on a crowded circuit
> Claims to be able to handle up to 100A!
board. :(
--
Never piss off an Engineer!
They don't get mad.
They don't get even.
They go for over unity! ;-)
Winfield Hill
Mar 6, 2017, 9:06:38 PM3/6/17
to
John Larkin wrote...
>
> We just demoed a cool new thermal imager ...
Names, please. And results, later.
--
Thanks,
- Win
>
> We just demoed a cool new thermal imager ...
Names, please. And results, later.
--
Thanks,
- Win
tom
Mar 6, 2017, 10:05:09 PM3/6/17
to
"Winfield Hill" <hi...@rowland.harvard.edu> wrote in message
news:o9l4j...@drn.newsguy.com...
John Larkin
Mar 6, 2017, 11:56:06 PM3/6/17
to
On 6 Mar 2017 18:06:30 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:
>John Larkin wrote...
>>
>> We just demoed a cool new thermal imager ...
>
> Names, please. And results, later.
I'm not sure I can name names yet. It's still in development.
We've become sort of a beta tester for these people. They send us
units and get our feedback, and we can keep them. Or maybe they just
like coming to San Francisco.
wrote:
>John Larkin wrote...
>>
>> We just demoed a cool new thermal imager ...
>
> Names, please. And results, later.
We've become sort of a beta tester for these people. They send us
units and get our feedback, and we can keep them. Or maybe they just
like coming to San Francisco.
gregz
Mar 7, 2017, 4:14:24 AM3/7/17
to
on boards.
Greg
Jeff Liebermann
Mar 7, 2017, 1:04:20 PM3/7/17
to
On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz <ze...@comcast.net>
wrote:
>I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
>on boards.
>Greg
Yes, but have you seen the prices?
<http://www.tek.com/current-probe>
The cheapest model that does DC is $1,600.
I rolled my own. I took an old Honeywell SS495A Hall effect sensor,
built a suitable amplifier, hot melt glued it to a piece of plastic,
and calibrated it by shoving DC through various PCB traces. It's
ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near
magnetic fields from xformers, inductors, steel mounting brackets,
wall warts, etc. However, it's cheap and easy. I don't use it for
troubleshooting very often.
The original suggestion sounds much like an RF current probe.
<http://www.lowfer.us/k0lr/currprob/currprob.htm>
<https://interferencetechnology.com/the-hf-current-probe-theory-and-application/>
However, these cannot be used to measure current though a PCB trace.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
wrote:
>I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
>on boards.
>Greg
<http://www.tek.com/current-probe>
The cheapest model that does DC is $1,600.
I rolled my own. I took an old Honeywell SS495A Hall effect sensor,
built a suitable amplifier, hot melt glued it to a piece of plastic,
and calibrated it by shoving DC through various PCB traces. It's
ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near
magnetic fields from xformers, inductors, steel mounting brackets,
wall warts, etc. However, it's cheap and easy. I don't use it for
troubleshooting very often.
The original suggestion sounds much like an RF current probe.
<http://www.lowfer.us/k0lr/currprob/currprob.htm>
<https://interferencetechnology.com/the-hf-current-probe-theory-and-application/>
However, these cannot be used to measure current though a PCB trace.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Cursitor Doom
Mar 7, 2017, 1:19:09 PM3/7/17
to
On Mon, 06 Mar 2017 20:56:02 -0500, Michael A. Terrell wrote:
> Let's see you use it to find a stray 100 mA DC on a crowded circuit
> board. :(
Oh come along now. You know it's not intended for that sort of usage!
> Let's see you use it to find a stray 100 mA DC on a crowded circuit
> board. :(
Cursitor Doom
Mar 7, 2017, 1:21:14 PM3/7/17
to
On Mon, 06 Mar 2017 20:56:00 -0800, John Larkin wrote:
> Or maybe they just like
> coming to San Francisco.
Unlikely. ;->
> Or maybe they just like
> coming to San Francisco.
gregz
Mar 8, 2017, 4:08:59 AM3/8/17
to
Jeff Liebermann <je...@cruzio.com> wrote:
> On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz <ze...@comcast.net>
> wrote:
>
>> I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
>> on boards.
>> Greg
>
> Yes, but have you seen the prices?
> <http://www.tek.com/current-probe>
> The cheapest model that does DC is $1,600.
>
> I rolled my own. I took an old Honeywell SS495A Hall effect sensor,
> built a suitable amplifier, hot melt glued it to a piece of plastic,
> and calibrated it by shoving DC through various PCB traces. It's
> ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near
> magnetic fields from xformers, inductors, steel mounting brackets,
> wall warts, etc. However, it's cheap and easy. I don't use it for
> troubleshooting very often.
>
> The original suggestion sounds much like an RF current probe.
> <http://www.lowfer.us/k0lr/currprob/currprob.htm>
> <https://interferencetechnology.com/the-hf-current-probe-theory-and-application/>
> However, these cannot be used to measure current though a PCB trace.
>
>
I was using a NASA owned probe. Thought about trying to make one.
> On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz <ze...@comcast.net>
> wrote:
>
>> I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
>> on boards.
>> Greg
>
> Yes, but have you seen the prices?
> <http://www.tek.com/current-probe>
> The cheapest model that does DC is $1,600.
>
> I rolled my own. I took an old Honeywell SS495A Hall effect sensor,
> built a suitable amplifier, hot melt glued it to a piece of plastic,
> and calibrated it by shoving DC through various PCB traces. It's
> ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near
> magnetic fields from xformers, inductors, steel mounting brackets,
> wall warts, etc. However, it's cheap and easy. I don't use it for
> troubleshooting very often.
>
> The original suggestion sounds much like an RF current probe.
> <http://www.lowfer.us/k0lr/currprob/currprob.htm>
> <https://interferencetechnology.com/the-hf-current-probe-theory-and-application/>
> However, these cannot be used to measure current though a PCB trace.
>
>
Greg
Winfield Hill
Mar 8, 2017, 8:44:57 AM3/8/17
to
Cursitor Doom wrote...
on my messed-up switching power-supply designs.
Qualitative results will be fine.
--
Thanks,
- Win
>
> Michael A. Terrell wrote:
>
>> Let's see you use it to find a stray 100 mA DC
>> on a crowded circuit board. :(
>
> Oh come along now. You know it's not intended for
> that sort of usage!
I ordered one from Newark, and plan to use it
> Michael A. Terrell wrote:
>
>> Let's see you use it to find a stray 100 mA DC
>> on a crowded circuit board. :(
>
> Oh come along now. You know it's not intended for
> that sort of usage!
on my messed-up switching power-supply designs.
Qualitative results will be fine.
--
Thanks,
- Win
Cursitor Doom
Mar 8, 2017, 9:55:35 AM3/8/17
to
On Wed, 08 Mar 2017 05:44:39 -0800, Winfield Hill wrote:
> I ordered one from Newark, and plan to use it on my messed-up switching
> power-supply designs.
> Qualitative results will be fine.
Mine arrived today. I plan to monitor fuel injection impulses with it
> I ordered one from Newark, and plan to use it on my messed-up switching
> power-supply designs.
> Qualitative results will be fine.
firstly just to see what kind of di/dt responses it's capable of. I'm not
quite as confident as you are, though!
Winfield Hill
Mar 8, 2017, 10:18:59 AM3/8/17
to
Cursitor Doom wrote...
I do a lot of fast HV pulsing circuitry, and don't
expect it'll be helpful for that kind of work. But
the 5MHz bandwidth should be fine for looking at
inductor current ramps, cap charge-discharge, etc.
--
Thanks,
- Win
expect it'll be helpful for that kind of work. But
the 5MHz bandwidth should be fine for looking at
inductor current ramps, cap charge-discharge, etc.
--
Thanks,
- Win
Jasen Betts
Mar 8, 2017, 7:02:11 PM3/8/17
to
(after removing it from the drum) to probe AC currents. It should be good
to a few megahertz. a core from an ethernet transformer with a gap
added could be another option. a spool-shaped inductor would
probably work too.
--
This email has not been checked by half-arsed antivirus software
John Larkin
Mar 8, 2017, 7:05:57 PM3/8/17
to
--
John Larkin Highland Technology, Inc
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
jurb...@gmail.com
Mar 9, 2017, 1:58:10 AM3/9/17
to
https://www.youtube.com/watch?v=bch1_Ep5M1s
Sorry I did not get the studio version, but this one looks interesting.
But I hate to say it, you will never catch me dead anywhere in California. Maybe fifty years ago but not today, even if I could afford the rents there.
Robert Baer
Mar 10, 2017, 1:43:30 AM3/10/17
to
John Larkin wrote:
> On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
> <cu...@notformail.com> wrote:
>
>> https://www.sparkfun.com/products/11005
>>
>> Replace the existing connector with a BNC, add a bit of series
>> resistance and you have a *very* cheap current probe for your
>> scope.
>
> On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
> <cu...@notformail.com> wrote:
>
>> https://www.sparkfun.com/products/11005
>>
>> Replace the existing connector with a BNC, add a bit of series
>> resistance and you have a *very* cheap current probe for your
>> scope.
>
> I have a clamp-on ammeter that pretty much does that, although it
> just indicates amps, and doesn't allow waveform snooping. 60 Hz
> waveforms aren't terribly interesting.
>
> just indicates amps, and doesn't allow waveform snooping. 60 Hz
> waveforms aren't terribly interesting.
>
> My real problem with current measurement is DC, on PC boards. We
> want to know how much current, say, an FPGA is using. Sometimes I
> include current shunts in a layout, but sometimes I don't.
>
> want to know how much current, say, an FPGA is using. Sometimes I
> include current shunts in a layout, but sometimes I don't.
>
> One can use existing switcher inductors as current shunts. I wish I
> had a PCB trace current probe, but that's probably not posssible.
> You can measure millivolt and microvolt drops across traces and
> vias.
>
>
>
>
You just described that PCB trace current probe; just use known trace
> had a PCB trace current probe, but that's probably not posssible.
> You can measure millivolt and microvolt drops across traces and
> vias.
>
>
>
>
length - with known width you get approximate current.
John Larkin
Mar 10, 2017, 1:04:16 PM3/10/17
to
resistors.
Cursitor Doom
Mar 11, 2017, 5:45:36 AM3/11/17
to
On Wed, 08 Mar 2017 22:58:08 -0800, jurb6006 wrote:
> Sorry I did not get the studio version, but this one looks interesting.
Certainly did!
> Sorry I did not get the studio version, but this one looks interesting.
> But I hate to say it, you will never catch me dead anywhere in
> California. Maybe fifty years ago but not today, even if I could afford
> the rents there.
of the Alta Mont free concert and that awful business involving Charlie
Manson and his 'Family' - and never recovered. :(
Tom Del Rosso
Mar 11, 2017, 4:22:19 PM3/11/17
to
John Larkin wrote:
> On Sun, 5 Mar 2017 16:18:50 -0000 (UTC), Cursitor Doom
> <cu...@notformail.com> wrote:
>> use at 60Hz, I would imagine. Hook it up to a 100Hz signal and
>> you'll see nothing at all in all probability. ;-)
>> what I can justify to splash out on as a mere hobbyist.
>
>
> A 1" long, 20 mil wide 1oz trace will be about 25 milliohms. 1 amp
> makes 25 millivolts, and lots of cheapish DVMs will resolve that well
> enough. You probably need a bench DVM with microvolt resolution to
> measure, say, 1 amp running through a via, but you could build a
> little microvolt meter or amp pretty easily. PCB trace and via
> resistances need to be calibrated, which is only a minor nuisance.
>
> Here are some pcb-trace shunts, down near the connector:
>
> https://dl.dropboxusercontent.com/u/53724080/PCBs/TEM2_Power_Board.JPG
>
> One of the great mysteries of electronics is "where is the current
> going?" Sometimes a thermal imager helps figure that out. A little
> magnetometer would be fun, not hard to do these days.
I once asked if a discarded head from an old, old hard disk could do
that.
There used to be a four-pin probe for PCB current measurement, in the
late 80s, but I can't find it. They're probably on ebay but I don't
know what name to search for.
---
This email has been checked for viruses by AVG.
http://www.avg.com
> On Sun, 5 Mar 2017 16:18:50 -0000 (UTC), Cursitor Doom
> <cu...@notformail.com> wrote:
>
>> On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote:
>>
>>> I have a clamp-on ammeter that pretty much does that, although it
>>> just indicates amps, and doesn't allow waveform snooping. 60 Hz
>>> waveforms aren't terribly interesting.
>>
>> Indeed they're not. But your meter is presumably *only* designed for
>> On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote:
>>
>>> I have a clamp-on ammeter that pretty much does that, although it
>>> just indicates amps, and doesn't allow waveform snooping. 60 Hz
>>> waveforms aren't terribly interesting.
>>
>> use at 60Hz, I would imagine. Hook it up to a 100Hz signal and
>> you'll see nothing at all in all probability. ;-)
>>
>>> One can use existing switcher inductors as current shunts. I wish I
>>> had a PCB trace current probe, but that's probably not posssible.
>>> You can measure millivolt and microvolt drops across traces and
>>> vias.
>>
>> Do they even exist? That would be amazing but no doubt *way* beyond
>>> One can use existing switcher inductors as current shunts. I wish I
>>> had a PCB trace current probe, but that's probably not posssible.
>>> You can measure millivolt and microvolt drops across traces and
>>> vias.
>>
>> what I can justify to splash out on as a mere hobbyist.
>
>
> A 1" long, 20 mil wide 1oz trace will be about 25 milliohms. 1 amp
> makes 25 millivolts, and lots of cheapish DVMs will resolve that well
> enough. You probably need a bench DVM with microvolt resolution to
> measure, say, 1 amp running through a via, but you could build a
> little microvolt meter or amp pretty easily. PCB trace and via
> resistances need to be calibrated, which is only a minor nuisance.
>
> Here are some pcb-trace shunts, down near the connector:
>
> https://dl.dropboxusercontent.com/u/53724080/PCBs/TEM2_Power_Board.JPG
>
> One of the great mysteries of electronics is "where is the current
> going?" Sometimes a thermal imager helps figure that out. A little
> magnetometer would be fun, not hard to do these days.
I once asked if a discarded head from an old, old hard disk could do
that.
There used to be a four-pin probe for PCB current measurement, in the
late 80s, but I can't find it. They're probably on ebay but I don't
know what name to search for.
---
This email has been checked for viruses by AVG.
http://www.avg.com
Tom Del Rosso
Mar 11, 2017, 4:32:01 PM3/11/17
to
John Larkin wrote:
> On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile <jda...@att.net>
> wrote:
>
>> They do make special current probes specifically for doing traces
>> on a PC board. without cutting traces or requiring a loop of wire.
>> <http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
>
> Looks expensive, and I'd guess not very accurate.
There's one on ebay now for $750.
> wrote:
>
>> They do make special current probes specifically for doing traces
>> on a PC board. without cutting traces or requiring a loop of wire.
>> <http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf>
>
> Looks expensive, and I'd guess not very accurate.
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