Enthusiast Power Protection: Four-Way 900 W UPS Roundup
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- Power
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Last response: in Reviews comments
Crashman
November 15, 2010 4:00:04 AM
It's downright negligent to ignore the power needs of your high-end hardware. While many power users go to the trouble of tracking down solid PSUs, we recommend going a step further and investing in battery backup. We round up four enthusiast units.
Enthusiast Power Protection: Four-Way 900 W UPS Roundup : Read more
Enthusiast Power Protection: Four-Way 900 W UPS Roundup : Read more
More about : enthusiast power protection 900 ups roundup
sudeshc
November 15, 2010 4:55:03 AM
hmp_goose
November 15, 2010 4:57:29 AM
Related resources
- 900w UPS enough to power or shut down a computer with a 850w power supply? - Forum
- Would a 450W UPS power a 900W rig for at least 10 secs? - Forum
dEAne
November 15, 2010 5:02:16 AM
Emperus
November 15, 2010 5:21:53 AM
Most folks would just be happy to ignore on the need for a backup power source.. Hope this article enlightens them on getting one to protect their precious components and/or be ready if and when the situation arises.. Would be great if Tom's could put up a tier based classification on suitable UPS choices for various PC's (gaming, server, home theatre etc.)..
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super_tycoon
November 15, 2010 6:03:37 AM
What about AVR? (Automatic Voltage Regulation) I have a CP1500AVRLCD and I've seen (at least I'm pretty sure) I've seen the AVR feature kick in when one of the local power lines got knocked out and the voltage drooped to ~100. (killed some of my non-dimmable cfl's) I went to CP's website and it claimed the pfc units still have AVR functionality. So here comes the confusion, what's the point of the voltage tolerances? If it has an AVR, why would it matter what voltage it's fed as long as there steps on the transformer? I thought the unit was supposed to take 90-140 without having to engage the battery while still passing ~120v?
You've also made me want to test my non-pfc ups with my 850hx, but my gaming rig and my workstation are an hour apart....
You've also made me want to test my non-pfc ups with my 850hx, but my gaming rig and my workstation are an hour apart....
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aldaia
November 15, 2010 6:27:12 AM
This is a quite inefficient & expensive approach to the problem. We take AC and use a transformer to convert to DC and store in a battery, meanwhile another transformer is also taking AC and converting to DC to feed our components. When there is a blackout, we take DC from the battery, convert to AC and feed the computer PS where we convert back to DC to feed our components. Wouldn't be more cost effective and energy efficient to use the same unit to both feed our components with DC and the battery? Most of the time a PS has a surplus of power that can be used to charge the battery. When there is a blackout we could just take DC from battery and feed our components without the inefficient double DC->AC->DC conversion. I think an integrated UPS/PS would be cheaper (most components are replicated). That would be enough for most enthusiasts, that only need a relatively short battery life to be able to save work. A different matter is in professional environments where a UPS feeds dozens of computers that cannot be stopped. ¿Anyone knows if such a think exists?
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16
wrxchris
November 15, 2010 7:47:34 AM
Anonymous
November 15, 2010 8:12:44 AM
g00ey
November 15, 2010 8:14:36 AM
I've always been wondering about the possibilities to replace the small batteries in those UPSes with standard car batteries or deep cycle (marine) batteries. Since the batteries in the UPSes are standard 12V lead cells it shouldn't be a problem and this would be a cheap way to keep the computer alive for days without external power.
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2
nebun
November 15, 2010 11:08:10 AM
g00eyI've always been wondering about the possibilities to replace the small batteries in those UPSes with standard car batteries or deep cycle (marine) batteries. Since the batteries in the UPSes are standard 12V lead cells it shouldn't be a problem and this would be a cheap way to keep the computer alive for days without external power.
wrong
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bull2760
November 15, 2010 12:27:40 PM
g00ey
November 15, 2010 12:39:41 PM
nebunwrong
No it's not wrong, a small UPS equipped with a bunch of low-cost standard deep cycle SMF/gel-cell batteries is a lot cheaper than a big UPS that comes factory equipped with that capacity. APC's Smart-UPS units come with ~2700 VAh and their price tags start at about $8000. Sure they are also able to provide up to 40 kW power from the batteries but this is far more than needed for home use.
The problems that may arise is that the inverter circuit may be too weak to operate for longer durations which is a problem among low-budget UPSes. It may not be able to run equipment for hours since its intended use to deliver power from batteries lies within a time-span of maximum half an hour. A sign to look for is if the UPS has cooling fans. Those that don't have that are probably not constructed for longer durations.
Another problem is that many of these UPSes are equipped with circuitry that monitor the health of the batteries. If you swap the original batteries with batteries that have higher capacity they will need more time to recharge and the circuitry may misinterpret this as that the batteries are "dead" since they don't take the charge at the same rate as is expected from smaller batteries.
The recharge voltage of the recharger circuit may not match the recommended voltage of the standard batteries if you use cheaper open-cell batteries. I've been told that the electrolyte of open-cell batteries tend to evaporate over time if you feed them with a higher than recommended recharge voltage. The solution to this is to make sure that the ventilation is good and keep refilling the cells with distilled water. Sealed gel-cell batteries should have the same recommended recharge voltages as those lead batteries that are used in the UPSes.
The solution to the last two issues could be to put on an additional (smart) recharger on the batteries that is connected to them 24/7 and let the battery/recharger circuit sit behind a rectifier just to be on the safe-side. This may of course confuse the battery health monitor circuitry of the UPS making it think that something is wrong with the batteries. If I had the budget I would definitely try these things out.
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3
g00ey
November 15, 2010 1:01:53 PM
bull2760I have a Tripp Lite power inverter hooked up to 3 90ahr batteries and I have 3 Servers connected into it, a cisco router, and a firewall. Works perfectlty.
I looked at them and if you want 120V power, they are good but if you want 230V then there is a problem. The models that provide 230V and are not crazily big (6 kW is far beyond household needs ...) use 12V as input. It's much better to use 48V or at least 24V as these setups with serially connected batteries can use thinner wiring. But this is an interesting option indeed since they come with an automatic utility power pass-through switch and a recharger.
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0
kureme
November 15, 2010 1:13:46 PM
mresseguie
November 15, 2010 1:27:27 PM
cyclocommuter
November 15, 2010 2:01:52 PM
I have an APC Smart-UPS 1500 and a Smart-UPS 700 and these have protected my computers for years. With the 1500, I did not even install the APC software, Windows 7 (and Vista) can interface with it directly via the OS' built in Power Management applet when the UPS is connected to the PC through the USB. They usually have these on sale at online stores for less than half the price from time to time. My smaller unit has been in service for more than 7 years and has undergone two battery changes. This is one advantage for APC Smart-UPS UPSes, replacement batteries are available in many places.
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bouncergriim
November 15, 2010 2:07:01 PM
joebob2000
November 15, 2010 2:19:08 PM
g00eyNo it's not wrong, a small UPS equipped with a bunch of low-cost standard deep cycle SMF/gel-cell batteries is a lot cheaper than a big UPS that comes factory equipped with that capacity.
In a word, "wrong" was the right answer. Ignoring everything else, for the simple reason that charge management isn't where it needs to be; you will destroy the UPS trying to charge and float anything behind 2x or 3x the normal capacity. There are vendors (apc is one of them at the entry level position in the market) that offer expandable runtime UPS solutions; if you are going to be relying on your backup and not just using it as a hobby project (there is nothing wrong with that) you are going to need a properly engineered solution.
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2
bpislife
November 15, 2010 2:46:17 PM
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-1
hellwig
November 15, 2010 3:04:14 PM
Sorry, I'm not buying the Sine Wave vs. Square Wave and zero-power state argument, pure PR BS (I've seen power strips promise this same Sine-Wave miracle technology, wonder what the excuse is there). I would love to see any UPS produce a true square-wave in the first place. Mathematically, it's impossible. In fact, BAD digital devices produce something closer to a sine-wave than a square-wave anyway.
I'd like to see Tom's test an old square-wave UPS, see if they can actually trigger an Active-PFC PSU shutdown on a swap to battery power. I'm guessing it won't have anything to do with the waveform coming out of the UPS.
And before you come back at me, I have a degree in Electrical Engineering, I actually have an educated basis for my beliefs.
I'd like to see Tom's test an old square-wave UPS, see if they can actually trigger an Active-PFC PSU shutdown on a swap to battery power. I'm guessing it won't have anything to do with the waveform coming out of the UPS.
And before you come back at me, I have a degree in Electrical Engineering, I actually have an educated basis for my beliefs.
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1
schm1tty
November 15, 2010 4:37:31 PM
jaquith
November 15, 2010 5:37:58 PM
misiu_mp
November 15, 2010 6:53:08 PM
kenyee
November 15, 2010 7:32:24 PM
You guys should also have tested Eaton (formerly Powerware) power supplies like the 9xxx series. Double conversion as well and quieter, though shorter run-times, but you can add external battery modules for longer runtimes if you need it.
I used to like APC SmartUPS until they started shutting down without warning when the battery was low. The newer ones seem ok so far...
I used to like APC SmartUPS until they started shutting down without warning when the battery was low. The newer ones seem ok so far...
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0
Hellwig, a true square wave would probably work as you say, but the "modified" sine waves don't simply cross the zero-line, they stay there for some fractional period of time.
I have a SG-650. It does not like the modified sine wave of a Back-UPS 750 at all, and shuts off right away. I had to get a SUA750 for it, and that works fine.
I was REALLY disappointed that these units, particularly the Cyberpower, were not tested with a PSU like that to see if they really worked. Also, why no scope shots of their waveforms, at low, moderate, and heavy load? This article gave a small taste, but I hope was only part I of II (or more).
I have a SG-650. It does not like the modified sine wave of a Back-UPS 750 at all, and shuts off right away. I had to get a SUA750 for it, and that works fine.
I was REALLY disappointed that these units, particularly the Cyberpower, were not tested with a PSU like that to see if they really worked. Also, why no scope shots of their waveforms, at low, moderate, and heavy load? This article gave a small taste, but I hope was only part I of II (or more).
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0
Crashman
November 15, 2010 8:29:10 PM
hmp_gooseSoooo you have nothing to say about the TripLite atoll? Dead last? Distant second? Muddled mess? Nice part for not-our-application?
I'd go with answer number four, which is covered in the page before the conclusionaldaiaWouldn't be more cost effective and energy efficient to use the same unit to both feed our components with DC and the battery?
That sounds like the way things are done in Notebooks. I've never seen anything like that for desktops, it seems like you'd need a 12-15VDC based power supply and a bunch of external parts to make it work.g00eyI've always been wondering about the possibilities to replace the small batteries in those UPSes with standard car batteries or deep cycle (marine) batteries. Since the batteries in the UPSes are standard 12V lead cells it shouldn't be a problem and this would be a cheap way to keep the computer alive for days without external power.
Well, hours anyway. I have converted used UPS's into low-cost power inverters, but I'm not sure they could handle the task of charging those big batteries. I also used an old 900VA unit with two 12V "hobby" batteries that were twice as thick as the original 6V units, for several years, because the hobby batteries were less than $10 each (two) and the replacement UPS batteries were over $40 each (four).jtt283Hellwig, a true square wave would probably work as you say, but the "modified" sine waves don't simply cross the zero-line, they stay there for some fractional period of time.I have a SG-650. It does not like the modified sine wave of a Back-UPS 750. and shuts off right away. I had to get a SUA750 for it, and that works fine.I was REALLY disappointed that these units, particularly the Cyberpower, were not tested with a PSU like that to see if they really worked. Also, why no scope shots of their waveforms, at low, moderate, and heavy load? This article gave a small taste, but I hope was only part I of II (or more).
The lab used here does not have an oscilloscope, and none of the available ones had the ability to interface a PC to record the waveform. All the companies were asked if they'd like to loan one, and all declined. This was particularly unfortunate for testing the Cyberpower unit.As for the sensitivity of various power supplies to waveform, the site couldn't find a list and had to take a guess as to which one to use!
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0
bjprice
November 15, 2010 9:32:54 PM
JackNaylorPE
November 16, 2010 12:35:53 AM
Was disappointed that there was no reference back to this article to see how these compared with the OCZ reviewed last year
http://www.tomshardware.com/news/ocz-ups-battery-backup...
Available at Amazon for $300 w/ purse sine wave power.
http://www.tomshardware.com/news/ocz-ups-battery-backup...
Available at Amazon for $300 w/ purse sine wave power.
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0
Crashman
November 16, 2010 2:01:39 AM
JackNaylorPE said:
Was disappointed that there was no reference back to this article to see how these compared with the OCZ reviewed last yearhttp://www.tomshardware.com/news/ocz-ups-battery-backup...
Available at Amazon for $300 w/ purse sine wave power.
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0
wotan31
November 16, 2010 3:03:55 AM
I don't care much for APC products. They set their float voltage too high, which cooks the batteries. 13.4 volts is correct for a 12v lead acid battery while APC uses 14.1 volts. You'll find yourself replacing batteries twice as often as with other brands. No thanks.
@hellwig, it isn't a true square wave from the less expensive UPS models. It's a "modified" sine wave. Like a square wave, but with very rounded off corners.
With audio equipment, there is a noticeable difference - you get loud buzzing and humm from the speakers with the "modified sine wave", while the true sine wave is nice and quiet. For a computer, it may or may not make any difference, I don't know.
@hellwig, it isn't a true square wave from the less expensive UPS models. It's a "modified" sine wave. Like a square wave, but with very rounded off corners.
With audio equipment, there is a noticeable difference - you get loud buzzing and humm from the speakers with the "modified sine wave", while the true sine wave is nice and quiet. For a computer, it may or may not make any difference, I don't know. Score
0
hmp_goose
November 16, 2010 5:20:20 AM
Crashman
November 16, 2010 5:31:14 AM
Crashman
November 16, 2010 5:36:00 AM
g00ey
November 16, 2010 8:17:05 AM
joebob2000 said:
In a word, "wrong" was the right answer. Ignoring everything else, for the simple reason that charge management isn't where it needs to be; you will destroy the UPS trying to charge and float anything behind 2x or 3x the normal capacity. There are vendors (apc is one of them at the entry level position in the market) that offer expandable runtime UPS solutions; if you are going to be relying on your backup and not just using it as a hobby project (there is nothing wrong with that) you are going to need a properly engineered solution.I understand that it in a sense may be "wrong" to do this even though I wish that the poster who made that comment motivated his statement and were more specific. However, the fact is that there are quite a few testimonials from people who have taken an old retired UPS and put some new sealed or unsealed deep-cycle batteries into it claiming that it has been working fine for years and successfully protected them from many power surges.
The "complaints" I have read about are the following: I've read some comments that the electrolyte tend to evaporate in unsealed batteries. The reason for this is that unsealed batteries are designed for a lower maintenance/float voltage than sealed gel/lead acid cells are. This was not perceived as a big issue as the batteries kept working as normal "for 5 years and still going strong" as long as one kept the cells filled with electrolyte by supplying distilled water.
Most people reported (in the forums that I've read) that their UPSes are able to keep the larger batteries fully charged or afloat as you call it. But after a power surge the recharger unit has problems recharging the battery. The most common comment about this is that "the batteries take a really long time to get fully recharged again". Some people say that they temporarily disconnect the batteries and recharge them using a normal recharger whenever that happens.
Most UPSes have some kind of a battery health monitor. Some designs however are too "smart" when it comes to replacing the batteries with batteries that have larger capacities for reasons I stated above in a prior post. Different ways to overcome this have been suggested. One suggestion is to modify the firmware of the UPS by changing the charge cycle times. There is a community somewhere working on an open-source version of the APC firmware allowing one to make such modifications.
Sure it could be debatable whether it is right or wrong to modify a UPS in such a way but I wouldn't go as far as to say that you are "destroying" the UPS by doing so.
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hangfirew8
November 16, 2010 1:10:27 PM
hellwigSorry, I'm not buying the Sine Wave vs. Square Wave and zero-power state argument, pure PR BS (I've seen power strips promise this same Sine-Wave miracle technology, wonder what the excuse is there).
Yeah I had to laugh at that sales pitch too. The "zero component" non-problem was actually a big improvement over the old square wave UPS's that had no zero component.
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0
hangfirew8
November 16, 2010 1:29:55 PM
g00eyI understand that it in a sense may be "wrong" to do this even though I wish that the poster who made that comment motivated his statement and were more specific.
g00ey, I don't see your idea as "wrong", obviously a decent experimenter can hack something together that works. I have done minor hacks such as replacing 5AH batteries with 7AH in little power-strip-like UPS's. The resulting recharge current requirements might strain the circuitry in a full discharge recovery situation, but not too much, so far no problem.
You've identified some of the caveats such as charge voltage, an AGM charger by itself will never bring a lead-acid battery to full charge. Keep in mind that even "sealed" lead-acid batteries have some hydrogen gas venting, and should be isolated from consumer indoor type electronics.
Auto starter type lead-acid batteries have a very low internal resistance on recharge, Marine deep-cycle a little more resistance, I could see a small consumer UPS tripping the circuit breaker (or frying something) attempting to recover a lead-acid battery from a deep discharge. This would be a fruitful area for experimentation.
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TheKurrgan
November 16, 2010 2:41:15 PM
nebunwrong
Hes not "wrong" persey... The statement of deep cycle marine would net him days of run time depending on how many deep cycle he used.. 6 20 pound 2 volt for example, tied together would net about 3 days at 400 watt draw using an inverter, cant see this being too different. As to a single 12V of any sort, hours -- not days will be the result. A car battery will go for around 5 hours depending on the size and condition. Also UPS devices that are modified to hook directly up to the cars power system (say for making a decent inverter instead of buying one) will NOT work. They are incapable of dealing with the raise in voltage produced by the alternator, and will shut down.
If you need large quantities of time with out AC power, here is a recipe:
1 800 - 1000 watt DC -> AC Inverter.
1 cheap preferably used small gas trimmer
1 1000 CCA Duralast battery
1 87 amp alternator from an old car
1 pulley
1 small V-Belt
1 15" high flow fan (for the trimmer)
150 ft of 20 amp drop cord.
5 gallons of gasoline
5 bottles of 2 stroke oil.
This will keep you gaming for about 6 hours before you NEED to start the trimmer with a new battery. Trimmer + Alt will totally carry the load and STILL be able to charge the battery with a max 800 watt inverter. Trimmer is a little on the noisy side, but a muffler can be attached (lawn mower mufflers are ok)
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0
sblantipodi
November 16, 2010 8:59:00 PM
shadowmaster625
November 18, 2010 12:35:47 PM
_rau_
November 18, 2010 11:58:38 PM
jtt283 Also, why no scope shots of their waveforms, at low, moderate, and heavy load? This article gave a small taste, but I hope was only part I of II (or more).
I ask the same thing, why no scope shots of the waveforms??? I'm very curious on the "Adaptive Sinewave" thing. I wonder how the wave looks like, if it looks closer to a true sinewave or closer to a stepped sinewave.
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Crashman
November 19, 2010 12:20:30 AM
_rau_I ask the same thing, why no scope shots of the waveforms??? I'm very curious on the "Adaptive Sinewave" thing. I wonder how the wave looks like, if it looks closer to a true sinewave or closer to a stepped sinewave.
Right, you quoted the question without reading the answer, now thumb me down and look for the answer in the thread. Score
1
_rau_
November 19, 2010 12:21:03 AM
sblantipodi said:
I hoped to see also the BR1500G series from APC in the article.This review focused on UPSes that outputs a true sinewave or something close to that, which is not the case for the BR1500G.
I've read your message on the APC forum, the issues your're having with APFC PSUs and you APC BR1500G. I think the Cyberpower Adaptive Sinewave is the answer until other brands like APC do something similar.
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0
_rau_
November 19, 2010 12:22:57 AM
g00ey
November 19, 2010 2:23:53 PM
There are a few cheap oscilloscopes out there. I've seen scopes that can go up to 50 MHz and be connected to a computer for about $200 including software. It is when you want an oscilloscope that can take measurements in the gigahertz range it gets expensive. But we are only interested in the 50-100Hz range so an oscilloscope in the kilohertz range would provide enough detail to assess the quality of the alternating voltage a UPS brings.
Also, the sound card of the computer can work as an oscilloscope and measure frequencies up to 22.05kHz/24Hz (for 44.1/48kHz sound cards - see the Nyquist rate in the sampling theorem) or 48kHz on better sound cards that support 96kHz sampling rates. You just use the Mic or Line In input of the sound card together with some oscilloscope software. I'm quite sure that there are freeware/open-source bundles available for this purpose. The oscilloscope data could then be processed in Matlab, Adobe Illustrator or even Microsoft Excel if you want the charts to look better and be easier to read. What you need in terms of additional hardware is some kind of a probe that can take 120/240V since that kind of voltage will obviously fry the sound card if not the whole computer. The high voltage probes that are available for professional oscilloscopes are not very expensive and are likely to work with the sound card using a proper BNC adapter. Otherwise you can also build one yourself. What distinguishes a high-voltage probe from a regular one is that it is coupled with a megaohm resistor. There should be instructions about it out there.
Also, the sound card of the computer can work as an oscilloscope and measure frequencies up to 22.05kHz/24Hz (for 44.1/48kHz sound cards - see the Nyquist rate in the sampling theorem) or 48kHz on better sound cards that support 96kHz sampling rates. You just use the Mic or Line In input of the sound card together with some oscilloscope software. I'm quite sure that there are freeware/open-source bundles available for this purpose. The oscilloscope data could then be processed in Matlab, Adobe Illustrator or even Microsoft Excel if you want the charts to look better and be easier to read. What you need in terms of additional hardware is some kind of a probe that can take 120/240V since that kind of voltage will obviously fry the sound card if not the whole computer. The high voltage probes that are available for professional oscilloscopes are not very expensive and are likely to work with the sound card using a proper BNC adapter. Otherwise you can also build one yourself. What distinguishes a high-voltage probe from a regular one is that it is coupled with a megaohm resistor. There should be instructions about it out there.
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0
Crashman
November 19, 2010 2:59:10 PM
g00eyThere are a few cheap oscilloscopes out there. I've seen scopes that can go up to 50 MHz and be connected to a computer for about $200 including software. It is when you want an oscilloscope that can take measurements in the gigahertz range it gets expensive. But we are only interested in the 50-100Hz range so an oscilloscope in the kilohertz range would provide enough detail to assess the quality of the alternating voltage a UPS brings.Also, the sound card of the computer can work as an oscilloscope and measure frequencies up to 22.05kHz/24Hz (for 44.1/48kHz sound cards - see the Nyquist rate in the sampling theorem) or 48kHz on better sound cards that support 96kHz sampling rates. You just use the Mic or Line In input of the sound card together with some oscilloscope software. I'm quite sure that there are freeware/open-source bundles available for this purpose. The oscilloscope data could then be processed in Matlab, Adobe Illustrator or even Microsoft Excel if you want the charts to look better and be easier to read. What you need in terms of additional hardware is some kind of a probe that can take 120/240V since that kind of voltage will obviously fry the sound card if not the whole computer. The high voltage probes that are available for professional oscilloscopes are not very expensive and are likely to work with the sound card using a proper BNC adapter. Otherwise you can also build one yourself. What distinguishes a high-voltage probe from a regular one is that it is coupled with a megaohm resistor. There should be instructions about it out there.
I hadn't even thought about using the microphone input...brilliant! Yes, it would need a very high resistor, but that certainly SOUNDS cheap. Score
0
g00ey
November 20, 2010 12:34:12 PM
I'm not sure if I would use the Mic port since it is rather sensitive but the Line In would do just fine. It is designed for signals with the voltage of 500mV to 2V so I would put at least a 10MOhm resistor on the probe circuit. The input impedance of the Line In ranges between 10kOhm and 47 kOhm on computer sound cards according to what I've read so I would put a "short-curcuit" resistor that has a resistance that roughly matches this impedance so as to protect the Line In. I would also make sure that the resistors can handle at least 5-10W. This kind of a circuit is called attenuator circuit and there are pre-built units for sale. For this kind of application a -24dB attenuator would be suitable.
Instructions on probe design can be found
here. It is a recommended read even though you would decide to buy a "professional" high-voltage probe or attenuator.
It could be worth mentioning that although I've seen implementations of this kind, I have never tried these things myself.
When I come to think about it, the sound card will probably only handle positive voltages. I seriously doubt that -2V would damage the sound card but the voltage will likely be outside its measurement range. I would solve this problem by using a small 1:1 transformer between the probe and the Line In and connect the Line In side of the transformer in series with a 1V power source. It is preferable that the power source is variable at least between 0.5 and 1V. This transformer is just as an extra precaution, I don't think it is necessary, you just have to make sure that its response lies well below 50Hz. When using this isolation transformer in such an application it is recommended to let the "short-circuit" resistor of the attenuator match the impedance of this transformer instead of the Line In. Just make sure that the peak voltage of the output/Line In side is below 1V to avoid clipping.
Instructions on probe design can be found
here. It is a recommended read even though you would decide to buy a "professional" high-voltage probe or attenuator.
It could be worth mentioning that although I've seen implementations of this kind, I have never tried these things myself.
When I come to think about it, the sound card will probably only handle positive voltages. I seriously doubt that -2V would damage the sound card but the voltage will likely be outside its measurement range. I would solve this problem by using a small 1:1 transformer between the probe and the Line In and connect the Line In side of the transformer in series with a 1V power source. It is preferable that the power source is variable at least between 0.5 and 1V. This transformer is just as an extra precaution, I don't think it is necessary, you just have to make sure that its response lies well below 50Hz. When using this isolation transformer in such an application it is recommended to let the "short-circuit" resistor of the attenuator match the impedance of this transformer instead of the Line In. Just make sure that the peak voltage of the output/Line In side is below 1V to avoid clipping.
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0
Kewlx25
November 22, 2010 10:51:03 PM
I have an APC 1500 back from 2002. It's almost 9 years old, still on the original battery. It has seen two lightning strikes that made the lights go crazy bright and blew out other devices, a couple of surges that made the light go bright, a few sags, and numerous power outages. Still getting 15-20min run times.
My first UPS was a Cyberpower 1200, but the first time I unplugged it to test, it started to smoke and I couldn't get it to turn off. A dark warped smoking spot of plastic started to form near the power button. That's when I returned it(Same day) and got my APC. My APC cost twice as much, but I'm happy with it.
It was probably just a defective unit, but come on. A short in the power button? really? It's like buying a new car and your horn doesn't work. It's that one thing that shouldn't ever not work.
Left a bad taste in my mouth with CP.
My first UPS was a Cyberpower 1200, but the first time I unplugged it to test, it started to smoke and I couldn't get it to turn off. A dark warped smoking spot of plastic started to form near the power button. That's when I returned it(Same day) and got my APC. My APC cost twice as much, but I'm happy with it.
It was probably just a defective unit, but come on. A short in the power button? really? It's like buying a new car and your horn doesn't work. It's that one thing that shouldn't ever not work.
Left a bad taste in my mouth with CP.
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-1
aragond
November 25, 2010 11:04:41 AM
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