Observations on a UPS - follow up to a previous post
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.
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?
Re: Observations on a UPS - follow up to a previous post
"Doc" <docsavage20@yahoo.com> wrote in message
news:1186963627.973618.37230@k79g2000hse.googlegro ups.com...
> 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.
>
> 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?
>
I would avoid hookihg it up to a motor driven appliance, as these generate
powerful surges when turned off that can blow semiconductor components. The
TV is fine.
Re: Observations on a UPS - follow up to a previous post
> 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.
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".
Re: Observations on a UPS - follow up to a previous post
In comp.sys.ibm.pc.hardware.misc Doc <docsavage20@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.
> 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.
Re: Observations on a UPS - follow up to a previous post
On Aug 12, 9:07 pm, Arno Wagner <m...@privacy.net> wrote:
> 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.
Re: Observations on a UPS - follow up to a previous post
"Doc" <docsavage20@yahoo.com> wrote in message
news:1186963627.973618.37230@k79g2000hse.googlegro ups.com...
> 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.
>
> 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?
>
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.
Re: Observations on a UPS - follow up to a previous post
>
> 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 $20 and those are all
more capable than large machines costing many thousands just a few decades
earlier.
Re: Observations on a UPS - follow up to a previous post
"James Sweet" <jamessweet@hotmail.com> wrote in message
news:ehPvi.2400$jy5.785@trnddc07...
>
> "Doc" <docsavage20@yahoo.com> wrote in message
> news:1186963627.973618.37230@k79g2000hse.googlegro ups.com...
>> 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.
>>
>> 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?
>>
>
> 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.
>
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.
Re: Observations on a UPS - follow up to a previous post
On Aug 12, 8:45 pm, "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.
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.
Re: Observations on a UPS - follow up to a previous post
On Aug 12, 10:24 pm, "James Sweet" <jamessw...@hotmail.com> wrote:
> > 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?
Re: Observations on a UPS - follow up to a previous post
"Doc" <docsavage20@yahoo.com> wrote in message
news:1187000538.571206.108700@r34g2000hsd.googlegr oups.com...
> On Aug 12, 10:24 pm, "James Sweet" <jamessw...@hotmail.com> wrote:
>> > 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?
>
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
Re: Observations on a UPS - follow up to a previous post
In comp.sys.ibm.pc.hardware.misc James Sweet <jamessweet@hotmail.com> wrote:
>>
>> 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.
Hmm. Interesting. I trust he did this right and tested non-ohmic
loads such as a PC PSU as well?
Re: Observations on a UPS - follow up to a previous post
> 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?
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.
Re: Observations on a UPS - follow up to a previous post
In comp.sys.ibm.pc.hardware.misc Doc <docsavage20@yahoo.com> wrote:
> On Aug 12, 8:45 pm, "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.
> 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.
Re: Observations on a UPS - follow up to a previous post
> Lead-acid batteries (like is [sic!] in your car) have major issues
> 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 $45 batter for the Sony D-T10.
Re: Observations on a UPS - follow up to a previous post
> But be aware that in general, these cheap 'power' meters
> are expecting
> 'traditional' sine-draw loads. I have seen wildly
> inaccurate standby figures being given for equipment, by
> eco-campaigners that have been let loose with one. A lot
> of modern equipment that makes use of switch mode power
> supplies, handles standby mode by brief bursts of full
> draw operation. This can confuse a simple power
> calculating algorithm that's expecting continuous draw.
> Also, the draw by many cheapo switchers is very asymmetric
> and 'dirty', and may also not produce a true reading.
>
> I wouldn't connect a UPS to a fridge. These things are
> notorious for pulling a short-term startup current of tens
> of amps, as they get the compressor turning over. The UPS
> would probably fall over before being able to supply this,
> and might, as someone else suggested, even sustain damage.
>
> Arfa
I have a "Kill-A-Watt" and it appears to display true RMS
for voltage and current readings. The voltage reading for a
modified sine wave from a standard UPS displays the actual
RMS voltage. I do not know what crest factor it can handle
but displays power factors of considerably less than unity
for most consumer electronics with DC rectifiers off of the
line voltage. It is a very nice unit for the price.
Re: Observations on a UPS - follow up to a previous post
"David" <someone@some-where.com> wrote in message
news:brYvi.13771$eY.11470@newssvr13.news.prodigy.n et...
>
>> 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
> 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. 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
>
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.
Re: Observations on a UPS - follow up to a previous post
Doc <docsavage20@yahoo.com> wrote:
>On Aug 12, 10:24 pm, "James Sweet" <jamessw...@hotmail.com> wrote:
>> > 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?
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."
Re: Observations on a UPS - follow up to a previous post
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:2KYvi.33164$vi3.30388@newsfe2-gui.ntli.net...
>
> "David" <someone@some-where.com> wrote in message
> news:brYvi.13771$eY.11470@newssvr13.news.prodigy.n et...
>>
>>> 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
>> 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. 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
>>
>
> 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
Arfa,
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.
Re: Observations on a UPS - follow up to a previous post
Arfa Daily wrote:
>
> 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/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.
Re: Observations on a UPS - follow up to a previous post
"David" <someone@some-where.com> wrote in message
news:brYvi.13771$eY.11470@newssvr13.news.prodigy.n et
> 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.
Re: Observations on a UPS - follow up to a previous post
On Mon, 13 Aug 2007 04:42:02 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:
>> Lead-acid batteries (like is [sic!] in your car) have major issues
>> 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.
>
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.
Re: Observations on a UPS - follow up to a previous post
On 13 Aug 2007 01:07:28 GMT, Arno Wagner <me@privacy.net>
wrote:
>In comp.sys.ibm.pc.hardware.misc Doc <docsavage20@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.
Re: Observations on a UPS - follow up to a previous post
"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.
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.
Re: Observations on a UPS - follow up to a previous post
Doc wrote:
> "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.
>
> 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.
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>
Re: Observations on a UPS - follow up to a previous post
"David" <someone@some-where.com> wrote in message
news:dvZvi.49369$YL5.33285@newssvr29.news.prodigy. net...
>
> "Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
> news:2KYvi.33164$vi3.30388@newsfe2-gui.ntli.net...
>>
>> "David" <someone@some-where.com> wrote in message
>> news:brYvi.13771$eY.11470@newssvr13.news.prodigy.n et...
>>>
>>>> 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
>>> 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. 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
>>>
>>
>> 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
> Arfa,
> 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
>
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.
Re: Observations on a UPS - follow up to a previous post
Doc wrote:
> On Aug 12, 8:45 pm, "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.
>
> 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.
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 :)
Re: Observations on a UPS - follow up to a previous post
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.
--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net>
Re: Observations on a UPS - follow up to a previous post
"Richard Crowley" <rcrowley@xp7rt.net> wrote in message
news:5ibfuhF3oi2e0U1@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?
Observations on a UPS - follow up to a previous post 
