Observations on a UPS - follow up to a previous post
Doc
getting an 875 VA 525 Watt "Geek Squad" model from Best Buy - yeah,
yeah, everyone says Geek Squad stuff is overhyped junk, but at $69 on
sale, the price seemed right.
It seems to handle my 2 computers fine - a PIV 2.4 gig and a PIII 933
mhz sharing a monitor. With both machines and the monitor on, the
onboard readout shows them well below the unit's max capacity, drawing
about .250 - .260 kw (which I assume translates to 250 - 260 watts) ,
with an estimated run time of 9 minutes with both computers. More than
enough to get me through short hit outages with both machines running.
Interesting to note how much of a difference the monitor makes.
Without the monitor - a 17" MAG CRT, the draw for both computers
drops under 200 watts and the estimate run time for the 2 computers
goes from 9 mins to 15mins. Over 20 mins with just one computer
running but no monitor.
Since this thing has a built-in watt usage meter, any reason I
couldn't hook it up to say a refrigerator or TV to check how much
wattage they're using?
Soundhaspriority
"Doc" <docsa...@yahoo.com> wrote in message
news:1186963627....@k79g2000hse.googlegroups.com...
powerful surges when turned off that can blow semiconductor components. The
TV is fine.
Bob Morein
Dresher, PA
(215) 646-4894
William Sommerwerck
> drops under 200 watts and the estimate run time for the 2 computers
> goes from 9 mins to 15mins. Over 20 mins with just one computer
> running but no monitor.
My experience -- at least where I live -- is that the power is off for a
fraction of a second, or hours. There's rarely anything in-between.
Than main advantage of an SPS -- again, in my area -- is protection against
the tenth-of-a-second glitches that have little or no effect on anything
else, but cause the computer to drop out. I've had as many as five or six in
a day -- imagine having to restart the computer each time, not knowing if
another might occur and slap you down again!
If you constantly save your work, a hard shutdown won't usually hurt you.
But it's always nice to have enough time -- during an extended power
outage -- to shut down the machine "rationally".
Arno Wagner
> Recently I asked about suggestions regarding a UPS. I ended up
> getting an 875 VA 525 Watt "Geek Squad" model from Best Buy - yeah,
> yeah, everyone says Geek Squad stuff is overhyped junk, but at $69 on
> sale, the price seemed right.
The price is all wrong. Nobody can build a decent product with
these specs for that price. You cannot even buy the components
needed in decent quality for that price.
> It seems to handle my 2 computers fine - a PIV 2.4 gig and a PIII 933
> mhz sharing a monitor. With both machines and the monitor on, the
> onboard readout shows them well below the unit's max capacity, drawing
> about .250 - .260 kw (which I assume translates to 250 - 260 watts) ,
> with an estimated run time of 9 minutes with both computers. More than
> enough to get me through short hit outages with both machines running.
And with the el-cheapo battery in there, that figure will be down to
<1 minute in no time. And you would be well advised to test the
claim. Software can be made to lie to you, you know.
> Interesting to note how much of a difference the monitor makes.
> Without the monitor - a 17" MAG CRT, the draw for both computers
> drops under 200 watts and the estimate run time for the 2 computers
> goes from 9 mins to 15mins. Over 20 mins with just one computer
> running but no monitor.
> Since this thing has a built-in watt usage meter, any reason I
> couldn't hook it up to say a refrigerator or TV to check how much
> wattage they're using?
A) the watt-meter is likely very crappy, given that a good AC
watt-meter costs more than this whole thing. They likely do a
current average and then some magic correction. Can be 50% off
or more even when used as intended. B) this device is
not intended to support motors.
Arno
Doc
> The price is all wrong. Nobody can build a decent product with
> these specs for that price.
Well, it was a sale price. I'm not sure that anything they sell there
is "top of the line".
> > It seems to handle my 2 computers fine - a PIV 2.4 gig and a PIII 933
> > mhz sharing a monitor. With both machines and the monitor on, the
> > onboard readout shows them well below the unit's max capacity, drawing
> > about .250 - .260 kw (which I assume translates to 250 - 260 watts) ,
> > with an estimated run time of 9 minutes with both computers. More than
> > enough to get me through short hit outages with both machines running.
>
> And with the el-cheapo battery in there, that figure will be down to
> <1 minute in no time. And you would be well advised to test the
> claim. Software can be made to lie to you, you know.
I'm going by the readout on the front of the gizmo, though it does
have software that gives many of the same readouts along with some
other tasks.
A test to find out how long it will actually run the computer sounds
like a good idea.
> > Since this thing has a built-in watt usage meter, any reason I
> > couldn't hook it up to say a refrigerator or TV to check how much
> > wattage they're using?
>
> A) the watt-meter is likely very crappy, given that a good AC
> watt-meter costs more than this whole thing.
Maybe, but a lot of people seem to swear by the Kill-A-Watt meter,
which can be had all day for around $25 online, eBay etc.
James Sweet
Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
are so popular, though I still prefer a good CRT as it looks slightly better
to my eyes.
Sure you can plug in other items, though motorized appliances will probably
not particularly like the modified sine wave those things put out.
Your best bet for that is to buy a Kill A Watt or similar device, they're
only about 25 bucks and will do so much more. You get accurate measurments
of watts, volts, amps, volt-amps, power factor, and accumulated kwa and you
can plug in anything you want.
James Sweet
>
> A test to find out how long it will actually run the computer sounds
> like a good idea.
>
>
That's a good way to kill the battery, these things tend to really punish
batteries, after a few complete cycles they're often pretty well toast. You
should be fine to try it for a bit, say 5 minutes without issues.
>
>
> Maybe, but a lot of people seem to swear by the Kill-A-Watt meter,
> which can be had all day for around $25 online, eBay etc.
>
>
EE friend of mine compared one to a $2500 power analyzer at work, found that
the Kill A Watt performance is pretty much inline with the specs printed for
it. It's not as good as the professional equipment, but it's really very
impressive for what it is and certainly adequate for consumer use. The
wonders of modern microelectronics, it's amazing what they can do with one
inexpensive chip and a handfull of passive components. I still remember when
a pocket calculator was $300, then a few years later $50 would buy one just
as effective, and not long after that they were under $20 and those are all
more capable than large machines costing many thousands just a few decades
earlier.
Arfa Daily
"James Sweet" <james...@hotmail.com> wrote in message
news:ehPvi.2400$jy5.785@trnddc07...
But be aware that in general, these cheap 'power' meters are expecting
'traditional' sine-draw loads. I have seen wildly inaccurate standby figures
being given for equipment, by eco-campaigners that have been let loose with
one. A lot of modern equipment that makes use of switch mode power supplies,
handles standby mode by brief bursts of full draw operation. This can
confuse a simple power calculating algorithm that's expecting continuous
draw. Also, the draw by many cheapo switchers is very asymmetric and
'dirty', and may also not produce a true reading.
I wouldn't connect a UPS to a fridge. These things are notorious for pulling
a short-term startup current of tens of amps, as they get the compressor
turning over. The UPS would probably fall over before being able to supply
this, and might, as someone else suggested, even sustain damage.
Arfa
Doc
wrote:
> My experience -- at least where I live -- is that the power is off for a
> fraction of a second, or hours. There's rarely anything in-between.
In general, I'd say that's my seat of the pants impression too, though
not always. I also notice they'll often come in clusters.
The transformer - if that's the correct term for it - big gray
basically cylindrical unit on top of a power pole - near my house blew
once. Powerful **BOOM** and a huge column of flame. Not sure what the
fuel for the flame was, do they have oil in them? Also a bit
disconcerting since anyone nearby surely would have been in jeopardy
from flaming debris.
Needless to say, power was out for a while on that one.
Doc
> > A test to find out how long it will actually run the computer sounds
> > like a good idea.
>
> That's a good way to kill the battery, these things tend to really punish
> batteries, after a few complete cycles they're often pretty well toast. You
> should be fine to try it for a bit, say 5 minutes without issues.
Seems I've heard an occasional complete drain-down and recharge will
extend the life of a rechargeable battery, that being constantly
partially discharged and recharged is what shortens their life. Not
so? Does it depend what kind of rechargeable it is?
Joseph Ashwood
It does depend on the battery. Early Lithium-Ion batteries benefitted from
the occassional full discharge, and Nickel-Metal Hydride batteries may
benefit from it. Lead-Acid batteries (like is in your car) have major issues
if they are completely drained, these are also the common battery in cheap,
well, just about everything. Newer Lithium-Ion batteries and Nickel-Metal
Hydride batteries have the controls in place so they don't benefit from a
complete drain. The Lithium-Polymer batteries that are beginning to appear
in some places do not benefit from complete drains, nor do they have
problems with overcharging, and now that they've gotten the self-ignition
problems eliminated look to replace just about everything but lead-acid.
So know your batteries, and you know the necessary behaviors, but really the
only problem ones are Lithium (non-rechargable) and Lead-Acid (damaged by
full drain).
Joe
Arno Wagner
Hmm. Interesting. I trust he did this right and tested non-ohmic
loads such as a PC PSU as well?
Arno
William Sommerwerck
> will extend the life of a rechargeable battery, that being constantly
> partially discharged and recharged is what shortens their life. Not
> so? Does it depend what kind of rechargeable it is?
You're thinking of nickel-cadmium batteries. The lead-acid batteries used in
these power supplies can be crippled or destroyed by a "full" discharge. Try
to avoid it.
Arno Wagner
> wrote:
>> My experience -- at least where I live -- is that the power is off for a
>> fraction of a second, or hours. There's rarely anything in-between.
> In general, I'd say that's my seat of the pants impression too, though
> not always. I also notice they'll often come in clusters.
> The transformer - if that's the correct term for it - big gray
> basically cylindrical unit on top of a power pole - near my house blew
> once.
Ugh. Putting them up for each individual hous is a very, very
historic way to do it.
> Powerful **BOOM** and a huge column of flame. Not sure what the
> fuel for the flame was, do they have oil in them?
Yes, for cooling. If it was an old transformer, you might have
giotten a nice load of Dioxins for free there...
> Also a bit
> disconcerting since anyone nearby surely would have been in jeopardy
> from flaming debris.
The right way to do this is to use bigger transformesr for 10-100 houese
and to bury 3-phase AC lines. A lot more expensive, but pays off
in the long run, since you have less problems. And all these ugly
poles and transformers will vanish.
> Needless to say, power was out for a while on that one.
I can believe that.
Arno
William Sommerwerck
> if they are completely drained, these are also the common battery
> in cheap, well, just about everything.
The _only_ consumer products I've owned that used lead-acid batteries were
an early Sony Discman, and two APC SPSs. They are not common in consumer
products. They provide relatively high capacity at a low cost (which is why
they're used in SPSs and UPSs), but they are too-easily damaged by a full
discarge. I accidentally ruined a $45 batter for the Sony D-T10.
William Sommerwerck
>> fraction of a second, or hours. There's rarely anything in-between.
> In general, I'd say that's my seat of the pants impression too,
> though not always. I also notice they'll often come in clusters.
Yes. The glitches are rarely isolated events.
Around my area, wind storms often cause sustained outages in areas where the
lines are above ground.
David
> But be aware that in general, these cheap 'power' meters
> are expecting
> 'traditional' sine-draw loads. I have seen wildly
> inaccurate standby figures being given for equipment, by
> eco-campaigners that have been let loose with one. A lot
> of modern equipment that makes use of switch mode power
> supplies, handles standby mode by brief bursts of full
> draw operation. This can confuse a simple power
> calculating algorithm that's expecting continuous draw.
> Also, the draw by many cheapo switchers is very asymmetric
> and 'dirty', and may also not produce a true reading.
>
> I wouldn't connect a UPS to a fridge. These things are
> notorious for pulling a short-term startup current of tens
> of amps, as they get the compressor turning over. The UPS
> would probably fall over before being able to supply this,
> and might, as someone else suggested, even sustain damage.
>
> Arfa
for voltage and current readings. The voltage reading for a
modified sine wave from a standard UPS displays the actual
RMS voltage. I do not know what crest factor it can handle
but displays power factors of considerably less than unity
for most consumer electronics with DC rectifiers off of the
line voltage. It is a very nice unit for the price.
David
Arfa Daily
"David" <som...@some-where.com> wrote in message
news:brYvi.13771$eY.1...@newssvr13.news.prodigy.net...
But that's my point. You can't have a 'true' sine-based RMS figure for power
consumers that draw a pulsed current. Just because it is a sine wave that's
*available*, it doesn't mean that the load will draw anything like a
sinusoidal current, from it. The only items that will are those that are
totally 'passive' in nature, such as light bulbs. Even power supplies that
are transformer based, are likely to draw current in pulses from the
available sinusoidal supply, and switch mode power supplies, on which most
modern consumer electronics are based, most certainly won't draw a
sinusoidal current from the supply.
Arfa
Scott Dorsey
It does not extend the life. Back in the seventies when NiCd packs had
memory effect, folks were recommending deep discharge. But today, you
are more likely to wreck a NiCd pack by reverse-charging a cell that way.
The cheap UPSes use gel-cells, which are gelled-electrolyte lead-acid
batteries. They are better at surviving deep discharge than NiCd packs,
but they still don't like it. Consequently, most equipment that uses
them will shut off when the battery voltage drops too low, to prevent
damage. Electronics are cheaper than batteries. Bigger UPS units use
liquid-electrolyte cells so you can check the battery condition with a
hydrometer periodically, and they also have a pulsed charging system that
prevents sulfates from building up on the plates. The Wal-Mart cheapies
probably do not.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
David
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:2KYvi.33164$vi3....@newsfe2-gui.ntli.net...
I know that the current draw on these things is anything but
sinusoidal. My point was that the "Kill-A-Watt" seems to
actually compute the RMS value for that complex current
waveform as well as non-sinusoidal voltage waveforms.
David
Michael A. Terrell
>
> But that's my point. You can't have a 'true' sine-based RMS figure for power
> consumers that draw a pulsed current. Just because it is a sine wave that's
> *available*, it doesn't mean that the load will draw anything like a
> sinusoidal current, from it. The only items that will are those that are
> totally 'passive' in nature, such as light bulbs. Even power supplies that
> are transformer based, are likely to draw current in pulses from the
> available sinusoidal supply, and switch mode power supplies, on which most
> modern consumer electronics are based, most certainly won't draw a
> sinusoidal current from the supply.
>
> Arfa
ICs to do the true RMS conversion are dirt cheap these days.
<http://www.analog.com/library/analogDialogue/archives/34-01/rmsarticle/index.html>
<http://www.analog.com/en/subCat/0,2879,773%255F866%255F0%255F%255F0%255F,00.html>
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
Arny Krueger
> I have a "Kill-A-Watt" and it appears to display true RMS
> for voltage and current readings. The voltage reading for
> a modified sine wave from a standard UPS displays the
> actual RMS voltage.
It is speced to deliver true RMS readings. It will also display power
factor.
> I do not know what crest factor it
> can handle
Can't find it in the manufacturer's detailed specs.
> but displays power factors of considerably
> less than unity for most consumer electronics with DC
> rectifiers off of the line voltage. It is a very nice
> unit for the price.
Agreed.
kony
Practically all consumer grade UPS use lead-acid batteries.
Other common items using lead-acid batteries are some of the
handheld halogen spotlight (flashlights), and automotive
portable power station "thing-a-majigs" like those that can
jump a car or have a flashlight/pump/inverter. A few
transportation devices have them also like a kid's motorized
big-wheels or skateboard or motorized bike, etc.
Any decently designed UPS will cut off power before the lead
acide battery is drained to a critical level, although it is
still much harder on the battery to drain to any significant
extent, a large % of total capacity instead of the UPS
turning off as soon as possible.
kony
wrote:
>In comp.sys.ibm.pc.hardware.misc Doc <docsa...@yahoo.com> wrote:
>> Recently I asked about suggestions regarding a UPS. I ended up
>> getting an 875 VA 525 Watt "Geek Squad" model from Best Buy - yeah,
>> yeah, everyone says Geek Squad stuff is overhyped junk, but at $69 on
>> sale, the price seemed right.
>
>The price is all wrong. Nobody can build a decent product with
>these specs for that price. You cannot even buy the components
>needed in decent quality for that price.
>
Depending on your definition of "decent", this may be true,
but it's going to be roughly equivalent to what you'd buy
from APC as a 500VA for about $50 so if that's what the
budget allows, it's not an exceptionally low price (also
considering you can sometimes get the APC discounted or with
rebate putting it closer to $20-30 than to $50.
>> It seems to handle my 2 computers fine - a PIV 2.4 gig and a PIII 933
>> mhz sharing a monitor. With both machines and the monitor on, the
>> onboard readout shows them well below the unit's max capacity, drawing
>> about .250 - .260 kw (which I assume translates to 250 - 260 watts) ,
>> with an estimated run time of 9 minutes with both computers. More than
>> enough to get me through short hit outages with both machines running.
>
>And with the el-cheapo battery in there, that figure will be down to
><1 minute in no time. And you would be well advised to test the
>claim. Software can be made to lie to you, you know.
There's no reason to belive the battery is especially cheap,
it's going to be a standard lead-acid which is quite a
mature technology today, a commodity item essentially and
all that's really at question is whether the manufacturer
conservatively rated the unit or if it's unlikely to meet
the specs due to design budget constructions. Either way,
it's probably $70-100 worth of UPS, it will likely do as
well as anything else available for the same price.
If one were to pay >= 2X as much, naturally the expectation
would be it's either fancier or higher capacity or an online
type, etc, but there is no expectation the battery is
inherantly any higher quality per se, though probably higher
capacity due to being a larger size or a series of two
batteries.
Richard Crowley
> "Doc" wrote...
>> Maybe, but a lot of people seem to swear by the Kill-A-Watt meter,
>> which can be had all day for around $25 online, eBay etc.
> EE friend of mine compared one to a $2500 power analyzer at work, found
> that the Kill A Watt performance is pretty much inline with the specs
> printed for it. It's not as good as the professional equipment, but it's
> really very impressive for what it is and certainly adequate for consumer
> use. The wonders of modern microelectronics, it's amazing what they can do
> with one inexpensive chip and a handfull of passive components. I still
> remember when a pocket calculator was $300, then a few years later $50
> would buy one just as effective, and not long after that they were under
> $20 and those are all more capable than large machines costing many
> thousands just a few decades earlier.
Agree completely. They are great when used with the regular
sine-wave mains power grid. However note that many have
been fried beyond repair when used with any kind of square-
wave source: inverter, UPS, etc. even "stepped sine" waveforms.
The problem appears to be the capacitive voltage divider used
to power the Kill-A-Watt electronics. The high frequency harmonics
deliver way too much power to the shunt regulator through the
capacitor and something fries.
Arfa Daily
OK. I'm not sure that 'RMS' is the right term to attach to any value derived
from a ragged-arsed waveform, as it is a mathematical function normally
associated with symetrical waveforms, which the draw by a SMPS may very well
not be, but I see what you're saying.
What I am trying to say is that a chip which is designed to produce an RMS
reading from a sine wave, may well produce a meaningful figure from a
non-sinusoidal waveform also, but *only* if it is still symetrical.
Arfa
Matt Ion
TRMOAS (that reminds me of a story)...
Years ago, when Atari ST computers were common, friends of mine lived in
and old house with just such a transformer on the adjacent pole.
Buddy had been trying for ages to get his girlfriend to start learning
to use the computer, but she was always afraid she'd "break something".
Finally one day, he convinced her to sit down and give it a try. She
took a deep breath, put her hands on the keyboard... as the room was lit
up by a brilliant flash through the window, shaken by a magnificent
**BOOM!**, and the computer screen went black.
Poor girl was in a complete panic, she was SURE it was her fault...
As it turned out, a drunk speeding down the road outside in his van had
gone THROUGH two nearby power poles and finally stopped just shy of
hitting a third; the first impact brought the lines down and was
sufficient to explode the transformer just outside their window.
...took her years to ever touch a computer again :)
Arny Krueger
news:5ibfuhF...@mid.individual.net
> "James Sweet" wrote ...
>> "Doc" wrote...
>>> Maybe, but a lot of people seem to swear by the
>>> Kill-A-Watt meter, which can be had all day for around
>>> $25 online, eBay etc.
>
>> EE friend of mine compared one to a $2500 power analyzer
>> at work, found that the Kill A Watt performance is
>> pretty much inline with the specs printed for it. It's
>> not as good as the professional equipment, but it's
>> really very impressive for what it is and certainly
>> adequate for consumer use. The wonders of modern
>> microelectronics, it's amazing what they can do with one
>> inexpensive chip and a handfull of passive components. I
>> still remember when a pocket calculator was $300, then a
>> few years later $50 would buy one just as effective, and
>> not long after that they were under $20 and those are
>> all more capable than large machines costing many
>> thousands just a few decades earlier.
Yup. I logged lots of hours on mechanical calculators, Wang shared-logic
desk calculators, and the HP35.
> Agree completely. They are great when used with the
> regular sine-wave mains power grid. However note that
> many have been fried beyond repair when used with any kind of
> square- wave source: inverter, UPS, etc. even "stepped sine"
> waveforms.
News to me. I've used mine with UPSs, but the application was not long-term
use.
> The problem appears to be the capacitive voltage divider
> used to power the Kill-A-Watt electronics. The high frequency
> harmonics deliver way too much power to the shunt
> regulator through the capacitor and something fries.
You're aware that capacitive voltage dividers have flat frequency response,
right?
Richard Crowley
> You're aware that capacitive voltage dividers have flat frequency
> response, right?
Perhaps you are not aware that many inexpensive consumer
mains power supplies use a capacitor rather than a resistor
as the series element of a shunt-regulated power supply.
The circuit is essentially a high-pass circuit and very much has
a rising response.
David
designs have a series and shunt capacitor and a small
resistor before the rectifier. This arrangement does have a
flat(er) frequency response. I may take my Kill-A-Watt apart
to see what they used in the design.
David
William Sommerwerck
I feel obliged to side with Arny. In the context of the original
description, it appeared as if the capacitive voltage divider was used to
drop the line voltage (as opposed to using a transformer). Putting a
capacitor in a shunt regulator is hardly the same thing.
Fred Kasner
Yes that transformer on top of the pole is what blew. The fuel was the
oil that acted as a dielectric insulator and heat dissipator. Older
versions have the liquid filled with PCBs (polybrominated biphenyls).
That stuff is quite hazardous.
FK
Fred Kasner
The ones with big "memory" problems were the generally no longer used
NiCad cells. They tended to lose capacity if not fully discharged now
and then.
FK
Gene E. Bloch
RMS is defined & well-behaved for *any* wave form.
It is, as its name implies, just the square root of the integral over a
time interval of V-squared, divided by the integration time.
In an attempt at ASCII math notation: sqrt [(1/T)*{integral from t0 to
t0 + T} V^2 dt]
It works best (esthetically) if T is very long, or at least a whole
number of cycles of the waveform.
What is *not* well-behaved for unusual waveforms is the shortcut
formula giving RMS as a factor times the magnitude of the peak voltage.
I forget: is it Vmax*[sqrt(2)]/2 ? Whatever the correct shortcut is, it
is only correct for a sine wave (or a rectified sinewave, as is
mathematically obvious) :-) )
--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")
Arfa Daily
"Gene E. Bloch" <spam...@nobody.invalid> wrote in message
news:mn.6bba7d785...@nobody.invalid...
I bow to your knowledge on this one, as you clearly have a better grasp of
the math involved than I. So are you saying that a meter that measures
*true* RMS anything - power, current, volts - will do so correctly even if
the waveform is asymmetric about the zero point ? I always believed ( was
taught ? - college seems so long ago now ... ) that even distribution about
the zero point, was a requirement for an accurate representation of an RMS
value ??
Arfa
William Sommerwerck
> if the waveform is asymmetric about the zero point? I always
> requirement for an accurate representation of an RMS value.
The RMS value of a waveform has nothing to do with the shape or symmetry of
the waveform.
Assuming the meter is correctly designed, yes. RMS has a clear, specific
definition, and if the measurement is correctly implemented, the reading
will be correct.
Two qualifications... If the waveform is non-periodic, the measured RMS
value will vary according to the sample period. Also, if the waveform
includes a DC component, and the meter blocks it with a capacitor, then the
RMS reading will not include the DC component.
James Sweet
>
> It does not extend the life. Back in the seventies when NiCd packs had
> memory effect, folks were recommending deep discharge. But today, you
> are more likely to wreck a NiCd pack by reverse-charging a cell that way.
>
I read recently that the memory effect "myth" was created due to cheap
chargers overcharging the batteries unless they were first fully discharged.
A decent intelligent charger should prevent this, and batteries have in
theory improved as well.
James Sweet
>
>> EE friend of mine compared one to a $2500 power analyzer at work, found
>> that
>> the Kill A Watt performance is pretty much inline with the specs printed
>> for
>> it. It's not as good as the professional equipment, but it's really very
>> impressive for what it is and certainly adequate for consumer use. The
>> wonders of modern microelectronics, it's amazing what they can do with
>> one
>> inexpensive chip and a handfull of passive components. I still remember
>> when
>> a pocket calculator was $300, then a few years later $50 would buy one
>> just
>> as effective, and not long after that they were under $20 and those are
>> all
>> more capable than large machines costing many thousands just a few
>> decades
>> earlier.
>
> loads such as a PC PSU as well?
>
Yes, of course, pure resistive loads can be measured just fine with a
multimeter. We were interested primarily in using it to measure discharge
lamp systems in which the power factor and current waveforms can be all over
the place and vary greatly with the state and condition of the lamp. If the
meter wasn't able to handle odd waveforms, the power factor measurement
function would be useless, but it works pretty well, accuracy is within
about 2% on the sample tested.
James Sweet
Interesting, well mine is the 240V UK version which I got back before I
found them offered here but from looking at the buttons and display it's
obviously the same unit as the Kill A Watt. At any rate I've tested it and
it works well all the way down to 60VAC, and frequencies from 30 Hz all the
way up to nearly 400Hz where the readings start to get screwy. I've run it
off inverters, used an adapter to hook it up to my 240V central heat pump to
measure that, it's taken everything I've tossed at it and so far keeps
working.
Doc
> > The transformer - if that's the correct term for it - big gray
> > basically cylindrical unit on top of a power pole - near my house blew
> > once.
>
> Ugh. Putting them up for each individual hous is a very, very
> historic way to do it.
I don't think there's one by every house, seems like you see them
every few poles.
> The right way to do this is to use bigger transformesr for 10-100 houese
> and to bury 3-phase AC lines. A lot more expensive, but pays off
> in the long run, since you have less problems. And all these ugly
> poles and transformers will vanish.
I know the power lines coming into my house are definitely above
ground. They're strapped to a supporting cable coming from a power
pole.
Doc
> >The price is all wrong. Nobody can build a decent product with
> >these specs for that price. You cannot even buy the components
> >needed in decent quality for that price.
>
> Depending on your definition of "decent", this may be true,
> but it's going to be roughly equivalent to what you'd buy
> from APC as a 500VA for about $50 so if that's what the
> budget allows, it's not an exceptionally low price (also
> considering you can sometimes get the APC discounted or with
> rebate putting it closer to $20-30 than to $50.
>
FWIW, I was in that same Best Buy today and the UPS model I got for
$69 was back to its normal price of $119.
James Sweet
>>
>> Ugh. Putting them up for each individual hous is a very, very
>> historic way to do it.
>
>
> I don't think there's one by every house, seems like you see them
> every few poles.
>
Generally it's 4-10 houses per transformer, it's nice, it makes it possible
to have quite good voltage regulation. I rarely see mine change by more than
a volt plus or minus.
>
>> The right way to do this is to use bigger transformesr for 10-100 houese
>> and to bury 3-phase AC lines. A lot more expensive, but pays off
>> in the long run, since you have less problems. And all these ugly
>> poles and transformers will vanish.
>
>
I'd love to have 3 phase, I've never seen it in a residence though, and
residential equipment is all single phase anyway, it works.
I kinda like above ground power, at least for the big stuff. Most of the
houses around here from the late 70s on have underground power, but some of
the old lines are starting to deteriorate so they've had to dig up streets
and flower beds to replace them.
Arfa Daily
"James Sweet" <james...@hotmail.com> wrote in message
news:ZQawi.3100$hK5.368@trndny02...
Isn't the 'high' voltage that you have in the US for powering washing
machines and the like, phase to phase ? Seems like it wouldn't be that hard
for the power company to put in the third phase as well ? (I might be
totally adrift on this one - I'm not a power engineer ;-) )
Arfa
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:94ednZl_M-fuZl3b...@comcast.com...
say, college seems a long-haired good music time ago now ...
Arfa
Doc
>
> Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
> are so popular, though I still prefer a good CRT as it looks slightly better
> to my eyes.
I don't like the way LCD/flat panel monitors look. The image isn't as
sharp and loses brightness unless you're sitting dead-center in front
of them, even the models that supposedly have a wider viewing angle.
Arno Wagner
Good to know, so it _can_ be done relatively cheaply today.
Arno
Arny Krueger
> residence though, and residential equipment is all single
> phase anyway, it works.
The German town I lived in during the late 70s had something like 440/3
phase which was used for the water heater. Obviously, it would work wonders
with motors.
As you no doubt know synchronous motors are the big thrill for 3 phase.
We seem to be making an end run on the issue by running DC motors through
transformerless AC-powered intelligent controllers.
> I kinda like above ground power, at least for the big
> stuff.
Interesting, because a lot of big stuff around here is underground until it
hits the neighborhood pole transformers. IOW, the next regional substation
up has all its ins and outs underground. Underground lines run to the
neighborhoods. They feed strings of poles in people's back yards.
Some people such as myself have converted their house feed to underground,
but it is pretty rare around here.
My application is peculiar - I live on a corner lot with a very narrow back
yard and lotsa trees. Also, my previouis above-ground drop was never code
and eventually failed. The part of the house where the power entry was no
longer exists.
Above-ground feed to the house was ugly no matter how it was done. The
utility's pricing scheme made the conversion to underground very
economically attractive, because my house needed a minimal length feed.
Their marketing people made up a price list with minimal initial costs and
buried most people's installation fees in the per-foot charge. I got quite
a bit of hardware and labor for my $250.
I hear that some utilities will convert people for free in some
neighborhoods.
> Most of the houses around here from the late 70s
> on have underground power, but some of the old lines are
> starting to deteriorate so they've had to dig up streets
> and flower beds to replace them.
Our neighborhood was built up from 1930 to 1955, so everything is above
ground. I've seen individual home conversions, but nothing on a neighborhood
scale.
Arny Krueger
> "Arny Krueger" wrote ...
>> You're aware that capacitive voltage dividers have flat
>> frequency response, right?
> Perhaps you are not aware that many inexpensive consumer
> mains power supplies use a capacitor rather than a
> resistor as the series element of a shunt-regulated power supply.
Right, but that's not a true capacitive voltage divider.
> The circuit is essentially a high-pass circuit and very
> much has a rising response.
Those half-breed RC voltage dividers do need to be engineered carefully.
Arny Krueger
news:5i9p6gF...@mid.individual.net
> In comp.sys.ibm.pc.hardware.misc Doc
> <docsa...@yahoo.com> wrote:
>> Recently I asked about suggestions regarding a UPS. I
>> ended up getting an 875 VA 525 Watt "Geek Squad" model
>> from Best Buy - yeah, yeah, everyone says Geek Squad
>> stuff is overhyped junk, but at $69 on sale, the price
>> seemed right.
Seems like it is discontinued - not on their current store list.
> The price is all wrong.
(1) Made in China, sold in the US
(2) House brand
(3) Close out
> Nobody can build a decent product
> with these specs for that price.
Best Buy is actually the high priced spread, compared to some of their
competition.
> You cannot even buy the
> components needed in decent quality for that price.
But that is unit one up individual component pricing which has a lot of
overhead in it.
Arny Krueger
news:1187092995.7...@b79g2000hse.googlegroups.com
Spend more money or wait 3 years! ;-)
Scott Dorsey
No, there actually _was_ memory effect at one time, and the Gates Battery
Handbook used to have a discussion about the chemistry involved. The
problem was solved some time in the late 1970s, but the notion on the part
of the users remained. And plenty of users since have destroyed perfectly
good battery packs by deep-discharging them and wrecking the weaker cells in
the pack, in order to avert a failure mode that hadn't existed for years.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Scott Dorsey
>>
>> I'd love to have 3 phase, I've never seen it in a residence though, and
>> residential equipment is all single phase anyway, it works.
>>
>> I kinda like above ground power, at least for the big stuff. Most of the
>> houses around here from the late 70s on have underground power, but some
>> of the old lines are starting to deteriorate so they've had to dig up
>> streets and flower beds to replace them.
>>
>
>Isn't the 'high' voltage that you have in the US for powering washing
>machines and the like, phase to phase ? Seems like it wouldn't be that hard
>for the power company to put in the third phase as well ? (I might be
>totally adrift on this one - I'm not a power engineer ;-) )
In the US, the high voltage distribution is done with three phases, shifted
120' from one another. You can also in many places order low voltage lines
with three-phase power, but it's not common in residential areas.
In most residential areas, they will send one leg of that three phase 3KV out
to a distribution transformer near your house. The secondary of that
transformer has a center-tap tied to the neutral, and then two hot wires
that are 180' out of phase. So neutral to one leg is 120V, but leg to leg
is 240V.
But this does not help you if you want to run a 25-foot turret lathe in
your garage, which requires three phases with a 120' shift between them.
For that, you either have to move to an industrial neighborhood, or call
the power company to pull three-phase 3KV in and then drop it down to
a low voltage with your own set of transformers. They will charge for this.
Arno Wagner
> Arfa Daily <arfa....@ntlworld.com> wrote:
>>>
>>> I'd love to have 3 phase, I've never seen it in a residence though, and
>>> residential equipment is all single phase anyway, it works.
>>>
>>> I kinda like above ground power, at least for the big stuff. Most of the
>>> houses around here from the late 70s on have underground power, but some
>>> of the old lines are starting to deteriorate so they've had to dig up
>>> streets and flower beds to replace them.
>>>
>>
>>Isn't the 'high' voltage that you have in the US for powering washing
>>machines and the like, phase to phase ? Seems like it wouldn't be that hard
>>for the power company to put in the third phase as well ? (I might be
>>totally adrift on this one - I'm not a power engineer ;-) )
> In the US, the high voltage distribution is done with three phases, shifted
> 120' from one another. You can also in many places order low voltage lines
> with three-phase power, but it's not common in residential areas.
> In most residential areas, they will send one leg of that three
> phase 3KV out to a distribution transformer near your house. The
> secondary of that transformer has a center-tap tied to the neutral,
> and then two hot wires that are 180' out of phase. So neutral to
> one leg is 120V, but leg to leg is 240V.
That would be 210V leg-to leg, because of the phase shift.
> But this does not help you if you want to run a 25-foot turret lathe
> in your garage, which requires three phases with a 120' shift
> between them. For that, you either have to move to an industrial
> neighborhood, or call the power company to pull three-phase 3KV in
> and then drop it down to a low voltage with your own set of
> transformers. They will charge for this.
Hmm. The typical approch in Europe is 15kV to large transformers
and then 3 phase distribution to the houses. Above ground is for
is moslty for rural areas, you do not see above ground lines in
cities, at least not in Germany or Switzerland. So getting three
phase is trivial. Typically flats have 3-phase times 16A (at 240V)
for electric stoves. Getting 3x25A at 240V is just some in-house
wiring. If you want 3x40A, you may need to have your feed checked,
since it is typically rated at 3x63A or 3x100A for larger houses.
Arno
Arno Wagner
If you select your LCD carefully, you can get really good ones
for very reasonable prices. I have a Benq FP73G, which initially
anoyed me a bit with the vertical brightness dependency on viewing
angle. Now I do not notice it anymore. It is sharper than CRT by
at least one order of magintude. Of course you have to run at
native resolution. As with brighness, I found that I needed to
tweak gamma in some games. apart from that, no problems.
Arno
Meindert Sprang
> I don't like the way LCD/flat panel monitors look. The image isn't as
> sharp and loses brightness unless you're sitting dead-center in front
> of them, even the models that supposedly have a wider viewing angle.
Then you should buy a decent flat panel. I went from an IIyama 22" CRT to an
IIyama 20" LCD and it is razorsharp compared to the CRT. And regarding
viewing angle: even watching from aside (175 deg.) it still looks like
watching a picture on a piece of paper.
Meindert
Scott Dorsey
>
>> In most residential areas, they will send one leg of that three
>> phase 3KV out to a distribution transformer near your house. The
>> secondary of that transformer has a center-tap tied to the neutral,
>> and then two hot wires that are 180' out of phase. So neutral to
>> one leg is 120V, but leg to leg is 240V.
>
>That would be 210V leg-to leg, because of the phase shift.
No, it's 180' phase shift. The two legs are directly out of phase,
therefore they sum. It's not three-phase, it's what they call
single-phase (even though it's really two phases).
CBFalconer
> "William Sommerwerck" <grizzledgee...@comcast.net> wrote:
>
>> My experience -- at least where I live -- is that the power is
>> off for a fraction of a second, or hours. There's rarely anything
>> in-between.
>
> In general, I'd say that's my seat of the pants impression too,
> though not always. I also notice they'll often come in clusters.
>
> basically cylindrical unit on top of a power pole - near my house
> what the fuel for the flame was, do they have oil in them? Also a
> bit disconcerting since anyone nearby surely would have been in
> jeopardy from flaming debris.
>
> Needless to say, power was out for a while on that one.
About 30 years ago a friend of mine was in a neighborhood where
multiple houses were supplied from one undersized transformer, and
the power company just ignored all requests to replace it. The
residents got together, and all turned on air-conditioners, ovens,
whatever, and then went outside to watch the transformer blow. It
did, and the scheme produced a new proper sized transformer.
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net>
--
Posted via a free Usenet account from http://www.teranews.com
CBFalconer
>
... snip ...
>
> OK. I'm not sure that 'RMS' is the right term to attach to any
> value derived from a ragged-arsed waveform, as it is a mathematical
> function normally associated with symetrical waveforms, which the
> draw by a SMPS may very well not be, but I see what you're saying.
>
> What I am trying to say is that a chip which is designed to produce
> an RMS reading from a sine wave, may well produce a meaningful
> figure from a non-sinusoidal waveform also, but *only* if it is
> still symetrical.
Oh? Try a square wave, for example. Nice and symetrical. You are
over-simplifying.
Richard Crowley
> "Richard Crowley" wrote ...
>> Agree completely. They are great when used with the regular
>> sine-wave mains power grid. However note that many have
>> been fried beyond repair when used with any kind of square-
>> wave source: inverter, UPS, etc. even "stepped sine" waveforms.
>>
>> The problem appears to be the capacitive voltage divider used
>> to power the Kill-A-Watt electronics. The high frequency harmonics
>> deliver way too much power to the shunt regulator through the
>> capacitor and something fries.
>>
>
> Interesting, well mine is the 240V UK version which I got back before I
> found them offered here but from looking at the buttons and display it's
> obviously the same unit as the Kill A Watt. At any rate I've tested it and
> it works well all the way down to 60VAC, and frequencies from 30 Hz all
> the way up to nearly 400Hz where the readings start to get screwy. I've
> run it off inverters, used an adapter to hook it up to my 240V central
> heat pump to measure that, it's taken everything I've tossed at it and so
> far keeps working.
There are rumors that the manufacturer re-designed the
circuit to eliminate this flaw. It may not be a problem with
newer models(?)
The original problem was featured in a 2-page article in the
ham-radio magazine "QST".
Richard Crowley
> "Richard Crowley" wrote
>> "Arny Krueger" wrote ...
>
>>> You're aware that capacitive voltage dividers have flat
>>> frequency response, right?
>
>> Perhaps you are not aware that many inexpensive consumer
>> mains power supplies use a capacitor rather than a
>> resistor as the series element of a shunt-regulated power supply.
>
> Right, but that's not a true capacitive voltage divider.
You are correct. I mis-characterized it as a "capacitive divider"
when only the series element was capacitive.
>> The circuit is essentially a high-pass circuit and very
>> much has a rising response.
>
> Those half-breed RC voltage dividers do need to be engineered carefully.
Rumor is that the manufacturer re-designed the circuit to
eliminate the problem.
SparkyGuy
> therefore they sum. It's not three-phase, it's what they call
> single-phase (even though it's really two phases).
> --scott
In common parlance it's known as "split phase", which is not technically
correct. Proper description of this is "3-wire, single-phase, mid-point
neutral system".
Sparky
Arny Krueger
> The transformer - if that's the correct term for it - big
> gray basically cylindrical unit on top of a power pole -
> near my house blew once. Powerful **BOOM** and a huge
> column of flame.
Been there, seen that, from a few blocks away. The boom was audible and the
fire was visible from that distance.
The old transformer in my back yard smoked for several hours, but neither
exploded nor emitted flames. The replacements were appreciably larger!
> Not sure what the fuel for the flame
> was, do they have oil in them?
Yes, most pole transformers are filled with some kind of insulating,
heat-transferring oily liquid. It may contain nifty stuff like PCBs, though
hopefully those have all been removed.
> Also a bit disconcerting
> since anyone nearby surely would have been in jeopardy
> from flaming debris.
There's a reason why they don't put these things in people's houses!
In fact oil-filled transformers are commonly put in dedicated rooms in
commercial buildings, but they have appropriate design and safety features.
> Needless to say, power was out for a while on that one.
We had a transformer blow in a local substation, and had rotating blackouts
for about a week. It was about the size of a small house, and the
replacement had to be trucked in from out of state.
kony
I should elaborate that roughly equivalent did not mean same
thing just spec'd less conservatively, did not mean to
include current capability and/or battery size, rather these
parameters were probably increased correspondingly.
kony
<ar...@hotpop.com> wrote:
>> You cannot even buy the
>> components needed in decent quality for that price.
>
>But that is unit one up individual component pricing which has a lot of
>overhead in it.
Quite true, practically anything electronic is this way.
Ironically even an empty project case can cost more than
some junk from China which is a complete product inside a
custom case.
kony
<docsa...@yahoo.com> wrote:
>On Aug 12, 10:24 pm, "James Sweet" <jamessw...@hotmail.com> wrote:
>
>>
>> Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
>> are so popular, though I still prefer a good CRT as it looks slightly better
>> to my eyes.
>
>
>I don't like the way LCD/flat panel monitors look. The image isn't as
>sharp
I'd have to disagree on this, if there is anything that is a
clear win for LCD, it is image sharpness... it doesn't get
any sharper than having individual pixel representation.
This can be offset in perception if the particular LCD has
poor contrast but it is still just as "sharp", though not as
vibrant.
> and loses brightness unless you're sitting dead-center in front
>of them, even the models that supposedly have a wider viewing angle.
True but it's a computer monitor, how many positions do you
really need to be in while viewing it?
David Lesher
>OK. I'm not sure that 'RMS' is the right term to attach to any value derived
>from a ragged-arsed waveform, as it is a mathematical function normally
>associated with symetrical waveforms, which the draw by a SMPS may very well
>not be, but I see what you're saying.
It's defined as heating value. Some RMS meters were in fact calorimeters.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
Scott Dorsey
>"Arfa Daily" <arfa....@ntlworld.com> writes:
>
>>OK. I'm not sure that 'RMS' is the right term to attach to any value derived
>>from a ragged-arsed waveform, as it is a mathematical function normally
>>associated with symetrical waveforms, which the draw by a SMPS may very well
>>not be, but I see what you're saying.
>
>It's defined as heating value. Some RMS meters were in fact calorimeters.
Bird still makes a couple models that are. Necessary as primary standards.
Gene E. Bloch
I agree with William Sommerwerck's more thorough analysis; the DC
problem (which I hadn't thought of) is pretty interesting too :-).
I agree about the confusion you mention - it makes sense; BTW, the way
around it is to use long sampling times, as I said in my post, although
I didn't go that one step further: to think about non-periodicity - &
understand it :-)
BTW, some true RMS meters use an entirely different approach[1]: they
measure the temperature of a resistor which is heated by the current
flowing through it when it is shunted across the line. This is (1)
potentially pretty accurate, and (2) probably very very slow to respond
to changes - i.e, an implied long sampling interval :-)
I guess we're OT here, but I admit that I'm having fun...
[1] Well, I'm not sure why I said 'different' - we haven't discussed
the method used, have we?
--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")
Gene E. Bloch
> On Tue, 14 Aug 2007 05:03:15 -0700, Doc
> <docsa...@yahoo.com> wrote:
>
>> On Aug 12, 10:24 pm, "James Sweet" <jamessw...@hotmail.com> wrote:
>>
>>>
>>> Yeah CRT monitors take a lot of juice, it's one of the reasons flat panels
>>> are so popular, though I still prefer a good CRT as it looks slightly
>>> better to my eyes.
>>
>>
>> I don't like the way LCD/flat panel monitors look. The image isn't as
>> sharp
>
> I'd have to disagree on this, if there is anything that is a
> clear win for LCD, it is image sharpness... it doesn't get
> any sharper than having individual pixel representation.
> This can be offset in perception if the particular LCD has
> poor contrast but it is still just as "sharp", though not as
> vibrant.
I wonder if Doc is running his LCD at a non-native resolution...
>> and loses brightness unless you're sitting dead-center in front
>> of them, even the models that supposedly have a wider viewing angle.
>
> True but it's a computer monitor, how many positions do you
> really need to be in while viewing it?
:-)
Gene E. Bloch
I spoke just a bit too soon - the calorimetric method was mentioned in
some recent posts in this thread that I just saw.
Arfa Daily
"Arny Krueger" <ar...@hotpop.com> wrote in message
news:VaKdnQYELJNuQlzb...@comcast.com...
spectacular thunderstorm that had been raging, and circling round my
location, for an hour or so. About 200yds up the road, where it ran out to a
dirt track, and no houses were yet built, was a pole, with a tranny on it
that I would guess to have been perhaps 3ft x 2ft x 2ft. It fed just the
farm in the field behind my house.
I was looking straight up the road, when the pole took what looked like a
direct hit. It probably actually wasn't direct, as I guess that would have
just vapourised the whole thing, but close enough anyway, that there was no
discernible delay between the stroke flash, and the bang, which was so loud
that I thought the vibration was going to bring the house down around me.
Anyway, as I continued to watch, half blinded, an orange glow like a plasma
ball started to grow around the top of the pole. It expanded out until it
looked the size of a small weather balloon, then just hung there for several
seconds. Then, without warning, the top of the pole - presumably the
transformer - just exploded with a huge bang, a sheet of flame, and a shower
of sparks. The orange ball was immediately dissipated. When I was able to
look again, the top of the pole was on fire. The whole street was without
power for 3 days.
When I went to look at the pole the next morning, there was just a charred
stump at the top. What was left of the tranny was on the ground, and of
course, the lines were down, but oddly intact, as they hung on the next pole
out across the field. The tranny was three phase 11kv to 240v I think. Three
lines plus one across the top, anyway. I don't know how much of this
pyrotechnic display was as a result of the 11kv, or of megavolts getting in
there from the lightning strike, but whichever, it was one of the most
spectacular things that I've ever seen.
I now live in a house further up the same road, and the pole and tranny were
moved from the roadside to the bottom of my neighbour's garden. A couple of
years back, the electricity company put in a new underground feed to the
farm, and came and took the overhead down. My neighbour asked them to leave
the pole, as he has a rather nice Russian Ivy growing up it, that is like a
huge bush, or tree even. Curiously, when the tranny was in place, the ivy
never grew closer than a foot or so to the platform where it was mounted.
Since it's gone, the ivy now grows right to the top, so obviously, plants
can sense the field around the high voltage components, and don't like it.
Makes you wonder whether there's anything in these claims that high voltage
overheads cause cancer in kids ...
Arfa
Arfa Daily
"CBFalconer" <cbfal...@yahoo.com> wrote in message
news:46C0B915...@yahoo.com...
> Arfa Daily wrote:
>>
> ... snip ...
>>
>> OK. I'm not sure that 'RMS' is the right term to attach to any
>> value derived from a ragged-arsed waveform, as it is a mathematical
>> function normally associated with symetrical waveforms, which the
>> draw by a SMPS may very well not be, but I see what you're saying.
>>
>> What I am trying to say is that a chip which is designed to produce
>> an RMS reading from a sine wave, may well produce a meaningful
>> figure from a non-sinusoidal waveform also, but *only* if it is
>> still symetrical.
>
> Oh? Try a square wave, for example. Nice and symetrical. You are
> over-simplifying.
>
Explain ?
Arfa
Arfa Daily
"kony" <sp...@spam.com> wrote in message
news:iuo3c3tafp82usl1o...@4ax.com...
> On Tue, 14 Aug 2007 05:03:15 -0700, Doc
> <docsa...@yahoo.com> wrote:
>
>>On Aug 12, 10:24 pm, "James Sweet" <jamessw...@hotmail.com> wrote:
>>
>>>
>>> Yeah CRT monitors take a lot of juice, it's one of the reasons flat
>>> panels
>>> are so popular, though I still prefer a good CRT as it looks slightly
>>> better
>>> to my eyes.
>>
>>
>>I don't like the way LCD/flat panel monitors look. The image isn't as
>>sharp
>
> I'd have to disagree on this, if there is anything that is a
> clear win for LCD, it is image sharpness... it doesn't get
> any sharper than having individual pixel representation.
<snip>
Agreed, but only if in native resolution, as others have said, and only if
what you are viewing is standing still. Even with the fastest LCD panels,
motion blur is still a problem, although probably more noticable at the
lower resolutions offered by 'standard' TV transmissions displayed on
standard LCD TV sets. Much as I like the picture on my (expensive)
widescreen HP LCD monitor, and given that I do agree with you about
sharpness, I still have to come down just on James' side in that I too think
that there is something fundamentally 'better' looking about a good fine
dot-pitch CRT monitor, but if you asked me to define "good" in this context,
I don't think that I could ...
Arfa
Gene E. Bloch
My interpretation: you seem to be saying that some meters produce an
RMS value by applying a simple factor to the peak value of the voltage,
and you seem to be saying that it works for any symmetrical wave form.
For a sine wave, as I mentioned elsewhere in this thread, this factor
would be (root 2)/2. CBFalconer mentioned a square wave as a
counter-example. Square waves are obviously quite symmetrical, but for
them, the magic factor is 1, assuming a perfect square wave. There's no
such thing, of course, but the factor is still pretty close to 1.
Arno Wagner
You are right. Somehow I read 120' there.
Arno
kony
<arfa....@ntlworld.com> wrote:
>Agreed, but only if in native resolution, as others have said, and only if
>what you are viewing is standing still. Even with the fastest LCD panels,
>motion blur is still a problem, although probably more noticable at the
>lower resolutions offered by 'standard' TV transmissions displayed on
>standard LCD TV sets.
Have you seen significant motion blur on a current
generation smaller LCD? It seems everyone is upsizing which
offsets the improvements being made.
CBFalconer
>>>
>> ... snip ...
>>>
>>> OK. I'm not sure that 'RMS' is the right term to attach to any
>>> value derived from a ragged-arsed waveform, as it is a mathematical
>>> function normally associated with symetrical waveforms, which the
>>> draw by a SMPS may very well not be, but I see what you're saying.
>>>
>>> What I am trying to say is that a chip which is designed to produce
>>> an RMS reading from a sine wave, may well produce a meaningful
>>> figure from a non-sinusoidal waveform also, but *only* if it is
>>> still symetrical.
>>
>> Oh? Try a square wave, for example. Nice and symetrical. You are
>> over-simplifying.
>
> Explain ?
The integral is peak voltage times current. Simple. Not 0.7 *
peak voltage. Current is also constant for resistive loads, not
proportional to voltage. RMS doesn't work.
James Sweet
>
> Isn't the 'high' voltage that you have in the US for powering washing
> machines and the like, phase to phase ? Seems like it wouldn't be that
> hard for the power company to put in the third phase as well ? (I might be
> totally adrift on this one - I'm not a power engineer ;-) )
>
It's a center tapped 240V transformer that feeds houses, washing machines
are 120V, but large loads like dryers, cook stoves, central AC, etc will
wire from hot to hot with a double pole breaker to get 240V, it's still
single phase.
Arfa Daily
> Arfa Daily wrote:
>> "CBFalconer" <cbfal...@yahoo.com> wrote in message
>>> Arfa Daily wrote:
>>>>
>>> ... snip ...
>>>>
>>>> OK. I'm not sure that 'RMS' is the right term to attach to any
>>>> value derived from a ragged-arsed waveform, as it is a mathematical
>>>> function normally associated with symetrical waveforms, which the
>>>> draw by a SMPS may very well not be, but I see what you're saying.
>>>>
>>>> What I am trying to say is that a chip which is designed to produce
>>>> an RMS reading from a sine wave, may well produce a meaningful
>>>> figure from a non-sinusoidal waveform also, but *only* if it is
>>>> still symetrical.
>>>
>>> Oh? Try a square wave, for example. Nice and symetrical. You are
>>> over-simplifying.
>>
>> Explain ?
>
> The integral is peak voltage times current. Simple. Not 0.7 *
> peak voltage. Current is also constant for resistive loads, not
> proportional to voltage. RMS doesn't work.
>
OK. Well in that case, I don't think that I was over-simplifying, because if
you have read the whole thread, you will see that it was I who questioned
the validity of attaching an RMS value to a non-sinusoidal waveform.
However, several posters then came back to me with considerable levels of
mathematical proof, to say that RMS was a valid notion for any waveshape or
symmetry factor, the only qualifiers being DC content or variable cycle
periodicity. Although it might not be too clear, that second paragraph was
more of a musing based on that. My original contention was that a power
meter (or whatever) designed to derive and display an RMS value from a sine
wave, would not give a meaningful reading from non-sinusoidal or
non-symmetrical drawing loads, such as a SMPS may be, for instance. The
replies suggested that the waveshape was immaterial, and that the chipset
could very easily still calculate a meaningful result. I was a little
sceptical about this, as it seemed to fly in the face of what I was taught
many years ago in college, but I bowed to what seemed to be superior
knowledge in the field.
Now, you seem to be saying something quite different ? Comments ?
Arfa
Arfa Daily
Well, certainly on LCD TV sets, yes. Oddly enough, I was looking at just
that in a store last night. They all had a studio-based news broadcast on
them, and it was superb as long as they were in the studio, where everything
was basically standing still, and properly lit. As soon as it cut to an OB
on the other hand, there was motion blur on them ALL. Some were worse than
others in that the blur was not just a function of panel speed, but also
drive artifacts. These were not cheap sets either. Many were from big name
houses. The larger screen sets actually seemed to fare somewhat better than
the small ones in my opinion, and the plasmas were a little better again,
but none of them produced what I would describe as a 'good' picture in this
respect, compared to a CRT set of any size or vintage - even my 10 year old
large screen Toshiba. There's a world of difference between LCD pixel
switching times in the mS bracket, and fast phosphor reponses down in the uS
range.
I actually think that at the moment, digital display technology - without
wishing to open up *that* can of worms again - lags behind CRT display
technology, by a significant amount. Next time you go to the cinema, look up
at the booth window and see if you can see film looping around the ceiling.
If you can't, then it uses one of those new-fangled DLP video projectors.
Sit back comfortably with your popcorn, and wonder what's happened to your
eyes, when the first car drives across the screen ... d;~}
Arfa
John Williamson
value of a current or voltage waveform was calculated by working out the
area inside the curve plotted over a full cycle, which then allowed you
to calculate an equivalent DC value. This involved counting squares on
graph paper of the plotted waveform or similarly counting squares on a
calibrated oscilloscope tube face. The earlier & most of the current
cheap meters that give an alleged RMS reading take a peak reading &
apply a correction factor of 0.707 to it (1 divided by the (near enough)
square root of 2), as that gives the right answer with a clean sine
wave, which is what most of these meters are used to measure. (Mains
power round here is near enough a pure sine wave that you can ignore the
error, as it's less than the accuracy of the meter)
The RMS value of a (theoretical) pure square wave is exactly the same as
the average of the absolute values of the positive & negative peaks, as
the value is either fully positive or fully negative, with, in theory,
no other value being present.
The most (theoretically) accurate way to measure RMS values is to use a
hot wire meter, which doesn't care what the waveform is, it just
measures the heating effect which is more or less frequency independent
& includes any DC offset automatically.
Tciao for Now!
John.
kony
Many people in their daily use cannot see any lag or
ghosting from 19" and smaller LCD computer monitors.
If you can't actually see it, does it matter if it exists?
I can play 50 FPS video or games running at over 50 FPS on a
19" LCD computer monitor and not see any problems except the
obvious lack of contrast (but with CRT I am spoiled in this
respect, having bought Diamondtron tube based monitors for
the last few I used myself before switching to primarily LCD
usage).
Arfa Daily
"John Williamson" <johnwil...@btinternet.com> wrote in message
news:atudnYbakL6...@bt.com...
Yes, all agreed, but the shape of the mains waveform is immaterial, unless
you are talking a purely resistive load like a light bulb. The point that I
have been trying to make all along is that when you are trying to measure
power, it's a function of both voltage and current draw, and in the case of
a SMPS, especially one that's in standby mode, the current draw from the
mains supply voltage, is very likely to be anything *but* sinusoidal.
Arfa
Arfa Daily
> On Wed, 15 Aug 2007 08:43:53 GMT, "Arfa Daily"
> <arfa....@ntlworld.com> wrote:
>
>
>>I actually think that at the moment, digital display technology - without
>>wishing to open up *that* can of worms again - lags behind CRT display
>>technology, by a significant amount. Next time you go to the cinema, look
>>up
>>at the booth window and see if you can see film looping around the
>>ceiling.
>>If you can't, then it uses one of those new-fangled DLP video projectors.
>>Sit back comfortably with your popcorn, and wonder what's happened to your
>>eyes, when the first car drives across the screen ... d;~}
>
>
> Many people in their daily use cannot see any lag or
> ghosting from 19" and smaller LCD computer monitors.
>
> If you can't actually see it, does it matter if it exists?
Well no, of course not. But I would be surprised if anyone actually couldn't
see it. I prefer to believe that it's a little bit of 'King's New Clothes'
syndrome, and people don't really *want* to see it, having just shelled out
a bunch of their hard-earned, on what they believed was going to be better
than they already had. Even my wife can see it, without any prodding from
me, and she's about as technical as a pound of oranges ...
> I can play 50 FPS video or games running at over 50 FPS on a
> 19" LCD computer monitor and not see any problems except the
> obvious lack of contrast (but with CRT I am spoiled in this
> respect, having bought Diamondtron tube based monitors for
> the last few I used myself before switching to primarily LCD
> usage).
Yes, there is the lack of contrast issue, which is not insignificant in
itself. My son plays video games on his PC at high frame rates also. He also
has an expensive HP 4:3 LCD, and whilst it's pretty good at displaying fast
motion, there is, never-the-less, motion blur that wasn't there when he used
CRT monitors. When a pixel represents decimals of a uS, and the time to
switch that pixel is around a mS at best, there must be motion blur created.
Arfa
John Williamson
the RMS voltage of the supply, as the input circuitry contains reactive
and regulatory elements that alter the phase relationships between the
current & the voltage in a manner that can't necessarily be predicted
easily.
Most of the ones I've looked at have a rectifier across the mains feed,
with inductive & capacitive elements in the circuit before the
rectifier, with a SMPS pulling power from the rectifier after a
smoothing filter. This gives a power factor that varies with load,
possibly cyclically even at steady load if the oscillator of the SMPS
isn't locked to the incoming mains frequency.
Then the invertor on the output just runs off the DC from the battery
pack/ SMPS combination.
As you say, though, the shape of the mains waveform is immaterial, apart
from harmonics altering the power factor by altering the relative
impedances of the inductors & capacitors.
Tciao for Now!
John.
Arny Krueger
>>> The most (theoretically) accurate way to measure RMS values is to use a
>>> hot wire meter, which doesn't care what the waveform is, it just
>>> measures the heating effect which is more or less frequency independent
>>> & includes any DC offset automatically.
That's one way, subject to the problems with accurately measuring the
heating of a resistive element.
Another way to obtain a true RMS reading without complex electronics is to
use a certain kind of meter movement that mechanically integrates the
product of the current and the voltage. There are two sets of windings in
the meter, one for current and one for voltage. Their attraction or
repulsion that drives the pointer is based on the product of the current in
the windings. I have one that was made by RCA, and a very common tool during
the 50s, 60s, 70s, and 80s.
>> Yes, all agreed, but the shape of the mains waveform is immaterial,
>> unless you are talking a purely resistive load like a light bulb.
Simply not true. Even light bulbs have some degree of sensitivity to the
waveform, unless they have filaments with very long thermal time constants.
Historically rectifier-based power supplies have been very sensitive to wave
form shape, because their output voltage is strongly influenced by the peak
value of the power line wave.
In the old days some magnetic power line voltage regulators put out a fairly
pure square wave. This did a pretty fair job of heating tube filaments, but
did not provide full B+ voltage from the power supply. The problem was the
low peak voltage. If you jacked up the line voltage to get full B+, the tube
filaments ran hot and tube life suffered.
> The point that I
>> have been trying to make all along is that when you are trying to measure
>> power, it's a function of both voltage and current draw, and in the case
>> of a SMPS, especially one that's in standby mode, the current draw from
>> the mains supply voltage, is very likely to be anything *but* sinusoidal.
Agreed. However there is a newer kid on the block, and that's the power
factor corrected SMPS. This technology has been reduced to an IC, and it
shows up in items as humble as compact flourescent light bulbs. If the
power factor is 1.00 or approaches it, then the current and voltage are
largely in-phase.
Andrew Erickson
"Arny Krueger" <ar...@hotpop.com> wrote:
> "John Williamson" <johnwil...@btinternet.com> wrote in message
> news:HZudnXJpGO8ccl_b...@bt.com...
>
> >>> The most (theoretically) accurate way to measure RMS values is to use a
> >>> hot wire meter, which doesn't care what the waveform is, it just
> >>> measures the heating effect which is more or less frequency independent
> >>> & includes any DC offset automatically.
>
> That's one way, subject to the problems with accurately measuring the
> heating of a resistive element.
>
> Another way to obtain a true RMS reading without complex electronics is to
> use a certain kind of meter movement that mechanically integrates the
> product of the current and the voltage. There are two sets of windings in
> the meter, one for current and one for voltage. Their attraction or
> repulsion that drives the pointer is based on the product of the current in
> the windings. I have one that was made by RCA, and a very common tool during
> the 50s, 60s, 70s, and 80s.
And a third practical way, which I suspect devices like the kill-a-watt
meter and "true RMS" digital multimeters use, is to sample the
voltage/current waveform and then use a microcontroller to perform the
appropriate integration. Microcontrollers are amazingly cheap and
powerful these days. As long as the waveforms you're measuring are
relatively slow (compared to the sampling frequency), it should be quite
accurate. For mains work, this isn't a hard thing to achieve--a few
kilohertz sampling rate is probably overkill.
--
Andrew Erickson
"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot
David
>> immaterial, unless you are talking a purely resistive
>> load like a light bulb. The point that I have been trying
>> to make all along is that when you are trying to measure
>> power, it's a function of both voltage and current draw,
>> and in the case of a SMPS, especially one that's in
>> standby mode, the current draw from the mains supply
>> voltage, is very likely to be anything *but* sinusoidal.
>>
>> Arfa
> It's also likely not to be a simple product of the RMS
> current drawn & the RMS voltage of the supply, as the
> input circuitry contains reactive and regulatory elements
> that alter the phase relationships between the current &
> the voltage in a manner that can't necessarily be
> predicted easily.
> Tciao for Now!
>
> John.
This all started with a discussion of the Kill-A-Watt meter
which measures RMS voltage, RMS current, and Watts. Maybe
the following will clear some of the confusion.
The computation of RMS was described in an earlier post. The
product of RMS voltage and RMS current is Volt-Amps. Power,
and therefore power consumption (Watts=power/second), is
computed by the integration of the product of instantaneous
volts and amps over time. The power factor then becomes
Watts/Volt-Amps. The accuracy of the wattage and RMS
calculations with voltage or current waveforms that change
rapidly is related to the sampling rate used in the
integration. Any wave shape for either voltage or current
will produce mathematically meaningful RMS and power
measurements. I am sure someone will point out any mistakes
I have made here.
David
CBFalconer
>
>> I can play 50 FPS video or games running at over 50 FPS on a> 19"
>> LCD computer monitor and not see any problems except the obvious
>> lack of contrast (but with CRT I am spoiled in this respect,
>> having bought Diamondtron tube based monitors for the last few I
>> used myself before switching to primarily LCD usage).
>
> Yes, there is the lack of contrast issue, which is not
> insignificant in itself. My son plays video games on his PC at high
> frame rates also. He also has an expensive HP 4:3 LCD, and whilst
> it's pretty good at displaying fast motion, there is,
> never-the-less, motion blur that wasn't there when he used CRT
> monitors. When a pixel represents decimals of a uS, and the time to
> switch that pixel is around a mS at best, there must be motion blur
> created.
I suspect that the real effect is caused by the pixel decay time.
CRTs operate with a refresh rate between 25 and about 100 hz,
depending on interlace, resolution, etc. This means a pixel will
be refreshed no sooner than 10 mS (up to about 40) from the earlier
energization. If, at that refresh time, the pixel has a
substantial carry-over from the previous level, there will be
blurring. If the carry-over is too small, there will be flickering
and other evil effects. I believe the LCDs have, effectively, zero
carry-over, and compensate by having an instantaneous reset of any
previously set level; i.e. they don't require interlace, refresh,
etc. except to show motion.
William Sommerwerck
Power is energy/second. Power is not consumed, energy is consumed.
William Sommerwerck
> factor corrected SMPS. This technology has been reduced to an IC, and it
> shows up in items as humble as compact flourescent light bulbs. If the
> power factor is 1.00 or approaches it, then the current and voltage are
> largely in-phase.
I checked some excellent CFLs from Home Despot (instant turn-on, excellent
color balance) with the Kil-a-Watt. It showed a power factor around 65%,
which struck me as rather low. Such a low PF also partly offsets the
money-saving advantages of fluorescent lamps.
Opinions, anyone?
Scott Dorsey
Well, your computer switcher probably has a power factor of about 1.2 to
1.5... so run a couple computers and the lead and lag will cancel one
another out...
Arny Krueger
> Opinions, anyone?
The dimmable CFLs I get from eBay (love those California lawmakers!) have PF
speced > 0.90. I haven't got around to testing one, though.
Gene E. Bloch
> Arfa Daily wrote:
>> "CBFalconer" <cbfal...@yahoo.com> wrote in message
>>> Arfa Daily wrote:
>>>>
>>> ... snip ...
>>>>
>>>> OK. I'm not sure that 'RMS' is the right term to attach to any
>>>> value derived from a ragged-arsed waveform, as it is a mathematical
>>>> function normally associated with symetrical waveforms, which the
>>>> draw by a SMPS may very well not be, but I see what you're saying.
>>>>
>>>> What I am trying to say is that a chip which is designed to produce
>>>> an RMS reading from a sine wave, may well produce a meaningful
>>>> figure from a non-sinusoidal waveform also, but *only* if it is
>>>> still symetrical.
>>>
>>> Oh? Try a square wave, for example. Nice and symetrical. You are
>>> over-simplifying.
>>
>> Explain ?
>
> The integral is peak voltage times current. Simple. Not 0.7 *
> peak voltage.
No, the integral is instantaneous voltage squared. Simple.
> Current is also constant for resistive loads, not
> proportional to voltage. RMS doesn't work.
You are contradicting Ohm's law, e = ir, which can be rearranged to
read i = e/r. Current is precisely proportional to voltage for
resistive loads. Simple.
I've used small letters to follow an old convention (is it still used?)
that lower-case letters represent varying values and upper-case letters
represent constant values (such as in analyzing DC circuits).
> --
> Chuck F (cbfalconer at maineline dot net)
> Available for consulting/temporary embedded and systems.
> <http://cbfalconer.home.att.net>
--
Gene E. Bloch
Great minds: I also call it Home Despot...
William Sommerwerck
> have PF speced > 0.90. I haven't got around to testing one, though.
What brand?
I bought a dimmable GE two years ago, and it worked. You get only about 10
steps, at the top of the X-10's 256-step range, but it works.
Arny Krueger
>> The dimmable CFLs I get from eBay (love those California lawmakers!)
>> have PF speced > 0.90. I haven't got around to testing one, though.
> What brand?
ULA, made you-know-where.
My understanding is that these bulbs are being sold in California for about
$1.00 each in Wal-Marts, with subsidy from the local power company.
> I bought a dimmable GE two years ago, and it worked. You get only about 10
> steps, at the top of the X-10's 256-step range, but it works.
The dimmable CFs I've been using have a standard Edison base and fit in
standard light bulb sockets. They are infinitely variable over a range that
goes down to pretty dark and then nothing, to full bright.
I use a few of them around the house, driven by standard wall-plate
residential dimmers.
I'm using 48 of them in 6 chandeliers driven by standard DMX-controlled
quad dimmer packs at church. Their brightness/drive curve is nonlinear, but
useable.
As you say, the color temperature is very constant over a usable range of
intensities compared to incadescent PAR bulbs. While they start pretty much
on the dime, they do get about 50% brighter the first minute or two of
operation.
If you've got the fixtures and ballasts that are designed for them,
4-terminal dimmable flourescents are marvelous. They dim over about the same
range of brightness and as linearly as an incadescent, but with constant
color temperature.
William Sommerwerck
> wall-plate residential dimmers.
Rheostats? Triacs? I'm not familiar with the current technology. (X-10 is
triac-controlled, I believe.)
> As you say, the color temperature is very constant over a
> usable range of intensities compared to incadescent PAR bulbs.
Actually, I didn't say that, but you'd expect it to be so, given that a
fluorescent lamp is a quantum device.
> While they start pretty much on the dime, they do get about
> 50% brighter the first minute or two of operation.
That's what I noted with the Home Despot lamps. It was startling at first to
see a fluorescent lamp come on faster than an incandescent.
Arno Wagner
>> I use a few of them around the house, driven by standard
>> wall-plate residential dimmers.
> Rheostats? Triacs? I'm not familiar with the current technology. (X-10 is
> triac-controlled, I believe.)
>> As you say, the color temperature is very constant over a
>> usable range of intensities compared to incadescent PAR bulbs.
> Actually, I didn't say that, but you'd expect it to be so, given that a
> fluorescent lamp is a quantum device.
Very much so, but mostly in the same sense that a glowing
pice of metal is a quantum device....
Arno
Gene E. Bloch
No, not at all in the same *sense*, but to the same *degree*. The
fluorescents use electron transitions in Hg to generate a line
spectrum, and then a fluorescent coating inside the bulb to convert the
lines in question into new lines and bands. This is in no way
comparable to black-body radiation, which is a continuum. This, of
course, is an *opinion* :-)
However, both are still quantum-mechanical devices at bottom. In fact,
it has been said that it was trying to solve the BB radiation problem
that led Planck to the discovery of his constant: he took the limit of
something as some differential went to zero and it didn't work. But he
got the right answer when he set the differential to a finite value,
around 6.27E-27, IIRC.
Close (sort of): Google gives me "Planck's constant = 6.626068 × 10-34
m2 kg / s", so I left out the second 6 - but I am used to it in cgs,
rather than mks, so the exponent is correct. That *would* be more
believable if I had expressed the units, erg-sec, above :-)