Any issues plugging test equipment into a UPS? - Page 1
Forum section: electronics / testgear

author: motocoder
author_rank: Unknown
timestamp: November 11, 2014, 06:40:10 pm
content: I salvaged an APC UPS (Back-UPS ES 350) whose only issue was a worn-out battery. I'm replacing the battery in it, and then was thinking of using it with my oscilloscope.I had a bunch of equipment fail after a recent windstorm induced power outage here. I am suspecting there was some sort of power surge before the power went out completely. I paid an arm and a leg for this scope, and am just wanting to make sure it's as protected from voltage surges as it can be, and I thought a UPS might be a good way to do that. Although I'm guessing this UPS is the kind that is not in the circuit until the power drops below some threshold, so maybe it's not providing all that much protection.I know most of these low-end UPS emit more of a square wave than a sine wave. Are there any issues with using that with test equipment, such as an oscilloscope? Please share any other thoughts you have on the best way to protect test equipment from mains power surges.Thanks

author: wraper
author_rank: Unknown
timestamp: November 11, 2014, 06:55:59 pm
content: Shouldn't be an issue, unless it switches to battery operation, there will be sine at the output. Unless it switches to battery operation, shouldn't introduce any noise to measurements too. However IMO such UPS offer very poor protection against rapid overvoltage conditions. Your equipment might be 10 times dead before it will click the relay.

author: Lightages
author_rank: Unknown
timestamp: November 11, 2014, 06:56:49 pm
content: You guessed it. The potential problem is the amount of noise the UPS injects onto the power line, specially if it is not a true sine wave output. If it is not a true sine wave, I wouldn't use it.

author: SeanB
author_rank: Super Contributor
timestamp: November 11, 2014, 07:23:13 pm
content: You probably would be better off looking for a line conditioner or constant voltage transformer, and find one locally to pick up, as they are heavy to ship. They are essentially a saturable reactor so that you get a constant voltage output as the input mains varies within limits.I have a 1kVA one, but rarely use it as it is a pretty good room heater, using around 300W in no load situations.

author: David Hess
author_rank: Super Contributor
timestamp: November 11, 2014, 07:57:36 pm
content: A UPS which produces a modified sine wave should work fine but I also question whether it will offer significant protection. Where I am in Missouri, we regularly get severe thunderstorms and I have my expensive computer and test gear plugged into an on-line UPS which has a sine wave output. Compact fluorescent lamps have a half life here of about 6 months.

author: MarkL
author_rank: Unknown
timestamp: November 11, 2014, 08:08:34 pm
content: We have power outages and dropouts often, and I have everything on my bench plus a local server on a 800W sinewave UPS. It's never caused any problems when switching to and running on battery.I agree with Lightages. I wouldn't connect anything I care about to a square wave (aka "modified sinewave") inverter. The high dV/dt of the square edge can cause a lot more current to flow into the input stage of power supplies, and it's sometimes more than they can withstand.I haven't seen anything fail lately on other peoples' square wave inverters, so perhaps overall power supply designs have improved. But I still think it's unwise to risk expensive test gear just to save a little money on the UPS.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: November 11, 2014, 08:43:47 pm
content: About 10 years ago I was using 3kVA APC UPSs to protect a small server room. The UPS capacity was designed to give us enough time to shut down the servers safely rather than to keep everything running. For a period the power supply at our location was not as reliable as one would wish. Spikes, brown outs and power cuts were quite regular for a year or so.We had no problem with spikes killing any equipment protected by the APCs, even though they did report over voltage. In retrospect that might have been helped by the inductive loads due to the Air Conditioning motors absorbing some of the energy.

author: motocoder
author_rank: Unknown
timestamp: November 11, 2014, 09:08:39 pm
content: I think all of the major-brand UPC also have some surge suppression circuitry in them.But maybe given the comments about the square wave output, I should just plug it into a good surge suppressor. I'm really not all that concerned about not being able to use the scope during the power outage.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 11, 2014, 09:22:51 pm
content: Quote from: motocoder on November 11, 2014, 09:08:39 pmPlug everything into a good quality Network surge protector like an APC network surge arrest. They have very fast clamping specs. Those APC UPS are not really square wave but stepped approximated waveforms. I've used them with no issues unless your power supplies are using power factor correction then you need pure sine wave.

author: DanielS
author_rank: Frequent Contributor
timestamp: November 11, 2014, 09:26:34 pm
content: Quote from: motocoder on November 11, 2014, 09:08:39 pmIf you do not care about your oscilloscope remaining powered-up during power outages, then there is not much of a point worrying about an UPS or the modified sine wave since the UPS' inverter switches in only when power is out; the rest of the time, power goes straight through, give or take whatever filtering and buck/boost (AVR) the UPS might do using passive components and some relays.Using an UPS instead of a surge protector does have the benefit of disconnecting your loads from mains when the power is out of tolerance so your load does not get exposed to transients again until line voltage has stabilized for more than a few seconds. With a surge suppressor, your devices get exposed to whatever let-through the suppressor might have for however long the abnormal voltage situation might last.

author: DanielS
author_rank: Frequent Contributor
timestamp: November 11, 2014, 09:48:57 pm
content: Quote from: Vito_R on November 11, 2014, 09:22:51 pmThe way many PFC controller chips cope with distortion is by simply bypassing the PFC function. As long as the primary caps stay above cut-off without the PFC voltage boost, everything is fine.Not all PFC circuits are designed the same though, so how much distortion they can gracefully cope with varies on a case-by-case basis. There certainly is no rule that says all APFC design have a total breakdown on non-pure-sinusoidal input - my PC's PSU is an Antec Earthwatt made by Delta, one of the manufacturers known for their often picky PFC, and it works fine with my ancient APC BX1000.

author: motocoder
author_rank: Unknown
timestamp: November 11, 2014, 10:07:14 pm
content: Quote from: Vito_R on November 11, 2014, 09:22:51 pmThat's the route I'm going - I just ordered an APC SurgeArrest.Quote from: Vito_R on November 11, 2014, 09:22:51 pmAre you sure all the APC units are that way? IIRC, they have two classes of units, and the lower end, consumer units don't do that. I think you have to buy the more expensive "Smart-UPS" to get the approximate sine wave output. This may have change, but I am pretty certain this was the case at one time.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 11, 2014, 10:09:50 pm
content: Quote from: motocoder on November 11, 2014, 10:07:14 pmThe Smartups series are pure sinewave. Their other models are stepped approximated waveform which looks like a squarewave with stairsteps in it.

author: denelec
author_rank: Regular Contributor
timestamp: November 11, 2014, 10:32:39 pm
content: Quote from: David Hess on November 11, 2014, 07:57:36 pmYou should consider buying a whole house surge suppressor:http://www.homedepot.com/b/Electrical-Power-Distribution-Whole-House-Surge-Protectors/N-5yc1vZbm05

author: MarkL
author_rank: Unknown
timestamp: November 11, 2014, 11:03:43 pm
content: Quote from: Vito_R on November 11, 2014, 10:09:50 pmNo, not all the "SmartUPS" branded units are sine wave. For example, the SmartUPS SC420, is not. You have to look at the spec sheets.And APC's marketing term, "Stepped approximation to a sinewave," is bull. It's a modified square wave. I purchased one last month for a non-critical application that didn't need sine wave and I looked at the output on a scope. It had two steps: One going positive and one going negative, accompanied by 0V in between steps so they get the right RMS output at the right frequency.They clearly state "Waveform type: Sine wave" on those units which are true sine wave. Not surprisingly, those are also the more expensive ones. And if any UPS or inverter doesn't say what type of output it has, you can bet it's not going to be sine wave.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 11, 2014, 11:36:17 pm
content: You're right about the stepped, I just checked one on the scope myself and didn't see a stair step just a square with some distortion. Guess their marketing can be deceiving. However they do work well and have proven to be reliable over the years. For more critical applications or use with PFC power supplies I'll always use a smartups. I have never purchased a smartups with a modified square output before, that I am sure of, but their may have been some specific versions that didn't have a true sine output. I just have never come across them.

author: GreyWoolfe
author_rank: Unknown
timestamp: November 11, 2014, 11:43:05 pm
content: I have 3 APC Smart-UPS1500s here in the office/ham shack. One handles my workbench where my test equipment resides. I have not had an issue. These big UPSs have voltage regulation built in. They work great, battery replacement is a bit pricey though.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 11, 2014, 11:54:34 pm
content: I don't trust anything but APC anymore just from personal experience. I tried once to give another cheaper UPS product a try I think it was called Cyberpower and it failed in one of my CCTV installations. The customer was really pissed and I had egg on my face from that. Not only that, when I tried to get any warranty replacement on it they wanted me to pay shipping both ways to them and the dealer that sold it to me wanted nothing to do with it. It wasn't worth it as it was just a smaller model. So I did a Dave teardown on it and found the culprit was a very poor design with a failed cheap chinese cap (of course) sandwiched between 2 very hot heatsinks cooking the poor little thing to it's death. I didn't even bother repairing the unit myself, I was so pissed off I just trashed it and replaced it with an APC. Learned my lesson.

author: motocoder
author_rank: Unknown
timestamp: November 11, 2014, 11:55:47 pm
content: Quote from: Vito_R on November 11, 2014, 11:36:17 pmThanks for checking into that. I actually tried to get this information off the APC site, but they have idiot-proofed their site so that now apparently only idiots can use it. The only way to get to product info is to navigate some UPS selector.

author: motocoder
author_rank: Unknown
timestamp: November 11, 2014, 11:57:15 pm
content: Quote from: Vito_R on November 11, 2014, 11:54:34 pmyep, I've got one CyperPower here - sitting right next to an APC. It's a piece of crap.

author: motocoder
author_rank: Unknown
timestamp: November 11, 2014, 11:58:52 pm
content: Quote from: GreyWoolfe on November 11, 2014, 11:43:05 pmThat is the big downside to the UPS. I have a number of the smaller ones scattered around the house, and it seems like every few months I'm having to replace the battery in one. I have had good luck getting cheaper replacement batteries off Amazon.com, though.

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2014, 12:23:38 am
content: Quote from: Vito_R on November 11, 2014, 11:54:34 pmI have never been happy with APC and partially for the reason motocoder identifies but I have also been avoiding all standby UPS units for years. I currently have a mix of refurbished Powerware and Leibert units.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 12:42:53 am
content: I'm surprised because they have been reliable as hell for me over the years. Batteries last me 3-4 years on average without issues.

author: gxti
author_rank: Frequent Contributor
timestamp: November 12, 2014, 02:39:37 am
content: Which CyberPower models did people have issues with? I have had 3x of their PFC-compatible (i.e. sinewave output) types for a few years now and I am extremely happy with them. I especially like that they have real USB and RS-232 ports, whereas APC tends to use modular jacks with random pinouts. I've had lots of trouble with the APC Back-UPS they replaced, granted it's APC's lowest-end line but it tended to cause things plugged into it to reset when it came back online after even the briefest blip of an outage or even on self-test. I still have it but at the moment it's only powering some monitors. Also doubles as a foot warmer.In terms of isolating delicate equipment nothing beats an online (double-converting) UPS because the inverter is always running and it essentially reconstructs the AC from scratch. But it costs a lot more and wastes power, and for the vast majority of equipment an offline sine-output UPS will do just fine for keeping things running.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 02:55:00 am
content: I have not tried any of Cyberpower's higher end ups nor do I ever wish to based on my own personal opinion and experience I had. It's not only the extremely poor design I saw in that piece of s** ups but the poor customer service and treatment by them when I tried to get warranty service on it. No dealer support either. Yes it was a smaller 350VA power bar style unit, but when I opened it up and saw the lack of respect for a basic design standard like thy shall not cook our capacitors between 2 hot heat sinks, I can never trust that brand again. APC has been rock solid reliable from my own personal experience with them so far and I will stick with them unless they try to pull such crap or cut costs that reduce product reliability.

author: gxti
author_rank: Frequent Contributor
timestamp: November 12, 2014, 03:04:03 am
content: I don't trust those "brick" type UPSes no matter who makes them, thermally speaking it's definitely a recipe for disaster. I can recall one from APC nearly went up in flames at work once so they're not immune from it either. You do have a valid point on support though -- I've never needed any for the CyberPower units I have but it's worth considering.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 03:11:07 am
content: I can't really agree cause i'm using those APC "brick" style ups on several smaller CCTV systems with no problems at all until now. Granted yes they are not going to perform as well as a full size tower style ups and I expect to change the batteries more often, but if they are designed properly with decent quality components they can last. I have one inside a closed cabinet in a garage location. Because the cabinet is very small I have no choice but to use one of those in that particular situation. Other situations are just based on cost restrictions and what the cheap a** customer is willing to pay.

author: wraper
author_rank: Unknown
timestamp: November 12, 2014, 03:20:33 am
content: Quote from: Vito_R on November 11, 2014, 11:54:34 pmI don't trust APC UPS at all. They are piece of junk. Every single APC UPS died at my job after a <5 years, half of them didn't survive 3 years, even 10kVA one. And all died by themselves, not because of the power surge, mainly because they used crap capacitors. Batteries they used in the cheaper (<$500) models were a cheap crap too which failed comparably fast. Of course if you compare APC to some china crap, they are better. We have many Powerware (now Eaton) UPS too, many of them work 10+ years without issues. Few newer Riello too, I like them because they are much quieter than new Eaton models.

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2014, 03:22:48 am
content: I do not remember which but at one time I had a 1200 watt Belkin or CyberPower and it would go through two 12V 7AH batteries in a year just sitting there doing nothing. I swapped the batteries once and then stopped using it.

author: wraper
author_rank: Unknown
timestamp: November 12, 2014, 03:25:28 am
content: Remembered that cheap models also died in a huge quantity at one subsidiary where voltage were unstable. The problem was that APC used crappiest relays made in India, they are even worse than Chinese according to one UPS repair forum.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 03:33:28 am
content: It's the opposite of what I've experience but I'll keep an eye on their newer models in operation and see if they have decided to crap out on quality too. So far though I can say i've been satisfied with them until my experience changes. If they used crap caps and relays then maybe I'll decide to upgrade and repair them myself. Problem is there's not much choice on the market in this price category. I'm just trying to stay away from the worst crap. It's sad when you have to simply say it's all junk lets just try to pick the best of the crap. Thanks to the made in china cheapening of our electronics industry we seem to be faced with that today.

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2014, 03:52:33 am
content: I have a pair of smaller Powerware Prestige EXT online UPSes which use five 12V 4AH batteries and instead of replacing the batteries when they wore out, I have continued to use the UPSes as power conditioners. I thought it might be fun to make a replacement battery pack using supercapacitors so they can handle momentary outages but it would not be very economical.

author: miguelvp
author_rank: Super Contributor
timestamp: November 12, 2014, 05:32:55 am
content: The only thing I wouldn't recommend to plug into a UPS is a laser printer. That's about the only equipment I had trouble with, of course I never did try to plug an AC unit, or a Fridge, or a Microwave, or a Washer or Dryer into a UPS

author: GreyWoolfe
author_rank: Unknown
timestamp: November 12, 2014, 01:10:00 pm
content: Quote from: wraper on November 12, 2014, 03:20:33 amMy 4 in-use APCs are approximately 10 years old. I grabbed them 3 years ago when we upgraded all the equipment out in the field. I also have 2 spares. The batteries still last a typical 3-4 years, and as I am using 2 of them for company use in my home office, the company will pay for the replacement batteries. I just have to worry about the other 2.In the 7 years they were out in the field, I can recall only replacing a few of them, and 1 was because the batteries swelled up so that they were not removable at the site. It was easier to replace and deal with at home-thank God our servers had 2 power cords so one could get plugged into the wall while removing the UPS and still keeping the site up.I will do what I have to to keep mine up and running. Power outage issues with Faulty-I mean Florida Power and Light is normally not much of a problem, but the automatic voltage regulation does get a workout, especially in the summertime.

author: GreyWoolfe
author_rank: Unknown
timestamp: November 12, 2014, 01:14:58 pm
content: Quote from: miguelvp on November 12, 2014, 05:32:55 amI was working on a Lexmark C720 color laser and, not thinking, plugged it into the power strip plugged into the UPS on my workbench. I could swear that the UPS started screaming instead of beeping when I pressed the power button. Everything that was turned on on the workbench shut off. Thankfully, no damage was done to any equipment, including the UPS. Even my small Brother desktop laser is plugged directly into the wall-lesson learned.

author: SeanB
author_rank: Super Contributor
timestamp: November 12, 2014, 05:51:20 pm
content: Funny the 10kVA UPS at work did not even notice when the 4MV monster was plugged into it, even with the 15A turn on current. Was did trip it every time was cold starting with all the PC PSU units charging up capacitors. I just sequence the breakers on the output in those cases, though the newer PC power supplies and the removal of all the CRT monitors did help a lot with that turn on surge.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: November 12, 2014, 07:26:30 pm
content: Looking over this thread, we find people with one or two (maybe a few) UPS's that have died in some way; so based on that sample they conclude that the manufacturer is cr@p. Then, other users who have a similar mix but, due to the vageries of statisitical sampling, has experienced no fails and can therefore only come to a polar opposite conclusion about the same manufacturer. You need a much bigger sample to get the true picture of relative manufacturer's reliability.I have ONE APC unit bought second hand, and it hasn't blown up (yet). It is about a year old, and having crawled over the insides it looks "pretty good" (and is the "smart" type) to me.Smaller, older UPS (including APC, I believe) have overly simple battery charging circuits, which can cause their batteries to die after only a couple of years.Do watch for anything that says "modified sine wave" (MarkettingBOLLOXfor square wave), or suspect similarly anything that DOESN'T clearly state "True sine wave output," As has been noted, the sharp rise times in the AC waveform can play havoc with poorly designed electronic loads. Smaller UPS's under (about) 500VA are more likely (but not exclusively so) to be squarewave, because they are cheaper to make, lighter (so cheaper to ship) and can be supplied with smaller batteries for the same effective runtime (due to their slightly better efficiency).Some products can work on square waves (often accompanied by lots of wining and squealing), while others will not. You find out by plugging them in, and seeing if the magic smoke stays in (or not).Laser printers tend to throw ANY (small) UPS, because at switch on most draw around 1kW (that's right) as the big heater comes on. This goes off after a few seconds, and then cuts in/out as required, but by then your 700VA UPS has already thrown in the towel.I would expect a UPS to handle blackouts, but if surges are a problem, I think I would look to a dedicated surge protection device. It's quite a different electrical fault to have to contend with. A modest UPC wont save ya.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 09:16:05 pm
content: Quote from: LaurenceW on November 12, 2014, 07:26:30 pmLaurenceW what is your opinion when a manufacturer designs a product and places an electrolytic capacitor sandwiched between the backs of 2 very hot heat sinks thus causing such part to fail? Do you think this represents good design practice and would have me instill confidence in their products? Add to that piss poor warranty support ?

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2014, 10:20:10 pm
content: Quote from: LaurenceW on November 12, 2014, 07:26:30 pmThe reason I do not like APC has more to do with their obfuscated marketing and poor customer support. I do not like Belkin not because their UPSes die but because they are poorly designed.

author: m100
author_rank: Regular Contributor
timestamp: November 12, 2014, 10:33:34 pm
content: Never had any need to plug test gear into a UPS these days but it will have happened in the past, not with anything made by APC though, something from this lothttp://www.piller.com- rated at a few hundred kVAP.S. APC UPS's have a habit of routinely overcharging the cells to reduce recovery time and they effectively cook them, to the extent they swell and may not even come out of the recess they are fitted into. There are mods detailed elsewhere online to knock the volts down a notch or two.

author: timb
author_rank: Super Contributor
timestamp: November 12, 2014, 11:29:54 pm
content: I use an Isobar on all my gear:http://www.amazon.com/gp/aw/d/B0000511U7Basically every pair of outlets is EMI/EMF isolated from the next pair of outlets so you don't get crossover.I can plug my scopes into one outlet, meters into another and PSUs into another and don't see any distortion on the scope when, say, the PSU changes transformer taps.It's good stuff.Sent from my Smartphone

author: LaurenceW
author_rank: Frequent Contributor
timestamp: November 12, 2014, 11:43:48 pm
content: Well, Vito_R, I can see that YOU have an opinion on APC!Look, I am not here to defend one manufacturer over another. Even Rolls Royces have a few cack design flaws, while a cheap Hyundai has some pretty clever (for the money) design ideas.Reality check - just about all UPSs (exclusion: the permenantly on, AC>DC>AC ones) spend only a tiny fraction of their lives under load, and then most probably not at full load. Yes, underrated heatsinks will get hot during this time, but personally I have seen no evidence of this being a real problem (as I mentioned earlier, you may have different experience, and so a different opinion).Let's remember the OP's question - Are there problems plugging test equipment into a UPS? the answer is - "there can be, it depends on a the sensitivity of the load, and the qulaity of the UPS" It's hard to be any more specific with the answer without knowing product codes and set-up.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 11:44:03 pm
content: Quote from: timb on November 12, 2014, 11:29:54 pmI agree, those Isobars are great, I have a couple too. They are pricey though, but worth it. Agree they would make a better surge protector for test equipment as they have superior RFI / EMI filtration and isolation. Very well designed.

author: Vito_R
author_rank: Regular Contributor
timestamp: November 12, 2014, 11:53:46 pm
content: Quote from: LaurenceW on November 12, 2014, 11:43:48 pmMy answer was not to state a positive opinion for APC but to state why I have lost complete confidence in another manufacturer. The issue was not about underrated heatsinks, it was about poor design practice and what I saw with my own eyes.