A stepped approximate sinewave can damage or affect my instruments? - Page 1
Forum section: electronics / beginners

author: mcinque
author_rank: Unknown
timestamp: August 19, 2013, 06:34:54 pm
content: Hello,I have recently moved into a new house, and I noticed a lot of voltage drops (I should have 220 ~ 230V, while I measured drops up to 180V: palm: and a maximum voltage of 210V).Since the entire neighborhood is experiencing the same problem (I suspect that there is an old power transformer to be replaced), I'm thinking of using a UPS online to solve temporarily the problem: I fear that this drops can damage prematurely the power supply of my instruments; am I wrong?Since all entry level UPS online models provide approximated sine wave output, I wonder if this can affect in any way my DSO or my function generator.What do you think about it? Should I buy a pure sinewave output version?

author: Rick Law
author_rank: Super Contributor
timestamp: August 19, 2013, 06:43:41 pm
content: I don't know about other equipment, but I do know that it could damage disk drives. When power goes too low, the drive motor may start and stop over and over. I had a few disks died that way.

author: ddavidebor
author_rank: Super Contributor
timestamp: August 19, 2013, 06:56:12 pm
content: You should buy a voltage stabilizer and not a ups.A online ups is much more expensive...

author: mcinque
author_rank: Unknown
timestamp: August 19, 2013, 08:09:17 pm
content: You're probably right ddavidebor, but I already own an APC Line-R 1200 voltage regulator: when the tension is under the limit and the device regulate the tension I can hear the typical switching noise coming out my speakers, so I guess the output goes in square wave or sinewave approximate.The question is: does make any difference to have a square wave or a sine wave as power sourcewith something different than hi-fi audio systems? If not, I can grab an UPS PRO 550 online for 120 $ to power the DSO and the function generator, what do you think?

author: AG6QR
author_rank: Frequent Contributor
timestamp: August 19, 2013, 09:27:14 pm
content: Quote from: mcinque on August 19, 2013, 08:09:17 pmThe answer depends on the design of the instrument's power supply unit. A lot of modern gear would use a switching power supply, which would be very forgiving of strange waveforms. On the other hand, such a power supply would probably also be very forgiving of random voltage fluctuations anywhere in the range of 110V to 250V, so the only benefit of a UPS in your situation would be to keep things running when the power stops completely.Check the data plate on the back of your DSO and function generator. What is the specification for the input supply voltage? If it's something like 110V-250V, you probably don't need to worry.

author: mcinque
author_rank: Unknown
timestamp: August 19, 2013, 11:22:43 pm
content: You are right AG6QR, if the PS accept from 110 to 220 I should not have problems.I've checked: only my function generator and my DSO can handle 110~220V directly.The other equipment (DMM and PSU) has the "well known" voltage selector on the rear, near the power plug.The PSU datasheet reports 207~250V limits, while the DMM reports 200~240V.In both cases, when the voltage suddenly drops, it decrease below the minimum level reported on the specifics (I've measured drops up to 180V);the "scary" thing is that sometimes it returns to an acceptable value (210V) after a fraction of a second.

author: digsys
author_rank: Unknown
timestamp: August 19, 2013, 11:52:48 pm
content: Your main question - will a stepped / modified sine wave / non-AC resonant converter harm equipment ?The short answer is - there isdefinitelya risk thatsometype of equipment will suffer, possibly fail.GENERALLY, it isn't devices with a reasonable S/Mode Input, as they convert to DC anyway. One caveat isthat some cheap simple converters generate a LOT of noise and spikes !! When it comes to TransformerInputs - things get tricky, depending on the how well the transformer is designed. Things like saturation,bias, and HF effects. Unfortunately, there's no real way of knowing except to try it. Not really a good solutionI'm afraid. Maybe put the line conditioner after the UPS?

author: ddavidebor
author_rank: Super Contributor
timestamp: August 20, 2013, 06:11:32 am
content: Quote from: mcinque on August 19, 2013, 08:09:17 pmYes transformers hate anything that is not sinusoidal and you will have tons of noise in your measurement. I mean TONS really,

author: poorchava
author_rank: Super Contributor
timestamp: August 20, 2013, 07:14:24 am
content: Quote from: mcinque on August 19, 2013, 08:09:17 pmI can see one concern though. Most of the power suppliers today have some form of PFC. Correct me if i'm wrong, but the PFC is supposed to make sure that current and voltage are in phase and load looks resistive. What bothers me though, is that all of the PFC controller chips are designed for sinewave input, not a square wave, so it's possible that they might go bananas and do something unpredicted (especially the cheaper ones from no-name suppliers).

author: G7PSK
author_rank: Super Contributor
timestamp: August 20, 2013, 07:16:52 am
content: I would start by complaining to the power company and the local trading standards (whatever they are called where you are) Italy is within the EU or was last time I looked and the EU lays down regulations about quality of power regulation, and power companies can be prosecuted if they do not do their best to ensure the standard is observed. So keep a log of the voltage drops and surges and if there is a pattern it is obvious that the power company is not doing its job.

author: mcinque
author_rank: Unknown
timestamp: August 20, 2013, 08:40:11 am
content: Quote from: digsys on August 19, 2013, 11:52:48 pmFor my PC I've an APC Back-UPS CS 650VA (a line interactive UPS) and a APC Voltage regulator and I cannot put the voltage regulatorafterthe UPS because the voltage drops make it switch (almost always) in battery mode. This drains very quickly the battery and all shuts down in about 9 mins.So I've put the voltage regulatorbeforethe UPS and lowered the sensitivity on the Power Chute software (otherwise at every LOW/NORMAL status change on the voltage regulator the UPS try to compensate going in battery mode for a couple of seconds).In this way I have voltage conditioning and back up power.But every time the voltage regulator goes in LOW tension mode, I can hear a low, typical square wave noise sound coming out on my PC loudspeakers (powered from the same circuit): I guess this is due to the switching / approximate sinewave output coming out from the voltage regulator.The point is that I don't know if using the same configuration (soproviding an approximate sinewave power output) for my PSU and DMM will affect something on that instruments (or their PS).It's better to have frequent awful voltage drops or a stepped sinewave?Quote from: G7PSK on August 20, 2013, 07:16:52 amI can't do it at the moment, I have to wait until I'm the real owner, not a tenant

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 20, 2013, 01:32:35 pm
content: other equipments with built in psu or regulator may survive no problem (most will full rectify anything that comes in), but most annoying thing is with heating element and excessively high powered equipements. water will boil slower, lights are dimmer, solder lead wont melt on iron, welding joint failure etc. our supplier is only one throughout the nation, so its a monopoly.

author: mcinque
author_rank: Unknown
timestamp: August 20, 2013, 02:32:15 pm
content: Quote from: Mechatrommer on August 20, 2013, 01:32:35 pmmmm, good to to know: I will not connect that devices to the regulator.However, attached to this post you can see the graphic data log that I've built today (a lucky day: not "too deep" voltage drops).On the Y you can read the Volts and on the X the number of the reading, taken every 2 seconds. All the data log was collected in about 1 hour.The maximum voltage is IMHO almost always below the minimum level for residential building (should be at least 220).I can't find a scheme inside, maybe the datalog is too short?

author: digsys
author_rank: Unknown
timestamp: August 20, 2013, 02:45:08 pm
content: Quote from: mcinqueIf that was an ECG readout, I'd smother the patient :-)

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 20, 2013, 04:06:57 pm
content: did you log on daylight? well, log for 24 hours (1 day) lets see. i bet the v will top during the day when all lights turned off. maximize your sleep during the night, work in the daylight as much as you canYMMV.

author: mcinque
author_rank: Unknown
timestamp: August 20, 2013, 08:13:52 pm
content: Quote from: Mechatrommer on August 20, 2013, 04:06:57 pmYes.Quote from: Mechatrommer on August 20, 2013, 04:06:57 pmI do not think that I can discover anything else than what I already know: my power line is crap

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 20, 2013, 09:06:53 pm
content: Quote from: mcinque on August 20, 2013, 08:13:52 pmretry at midnight then...Quote from: mcinque on August 20, 2013, 08:13:52 pmthe point is, you try to figure out when your neighboorhood is lowest on e consumption, thats when the highest v level and best time to work on, sweet spot so to speak.if it happen to be in the midnight or at 3AM (when everybody sleep and lights off) then maximize your sleep during the day!