Testing for slight power fluctuations in home

Old 12-05-23, 08:54 AM
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Testing for slight power fluctuations in home

Over the last few weeks, the UPS on two different computers are clicking briefly. I suspect that there is a very slight and super short (maybe just 1/2 a second) fluctuation in power that's making them react. How can an electrical idiot like myself test for that without putting my life at risk? Is there some I can hook up to an outlet that will let me see the voltage?

And should I call the power company? or an electrician?

Old 12-05-23, 09:32 AM
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For something very brief like you are seeing I would assume it's coming from the power company. I have experienced minor power blips, UPS clicking active or light bulbs dimming. I've very rarely been able to assign a specific cause.

There are devices like Kill-A-Watt that you can plug into an outlet and it will display the voltage. Many UPS and line conditioners also display the line voltage. If you want to use a "tool" you can also use a multimeter or voltage tester to monitor the voltage.

One thing you will find is that many devices smooth the voltage displayed. They may show the average voltage over a second or several second period. Good for seeing the voltage in general but possibly too short to spot a transient drop. I have a UPS and line conditioner on my entertainment system and have never noticed anything during brief voltage variations but it is fun to see that the voltage is low on super hot or cold days when everyone is running their AC or heat as hard as they can.
Old 12-05-23, 10:05 AM
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Many UPS' have a USB port and can be connected to a computer to either see real-time or download a report of the power fluctuations. Also many have sensitivity settings as well, so if you find it's switching too often, you can set it to a lower sensitivity so it's not constantly switching to battery.

There are also lots of power-monitoring devices with apps available. Most are no-name brand, but also quite inexpensive ($30-50) if you're really curious.
The last time I looked for something like this, monitoring systems were in the $500-1000+ price range.

But as Dane mentioned, it's likely not anything to be concerned with.
Old 12-05-23, 11:19 AM
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In each voltage cycle from the poco, the voltage is positive for approximately 8 milliseconds with equal time for the negative half. The only power-monitoring devices that has time resolution and trigger selection to view a voltage anomaly occurring within 8 milliseconds is an oscilloscope.
Old 12-05-23, 05:46 PM
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The only way a UPS can keep up the voltage in case of a dip from the power company is to use its backup battery. This may be why you are hearing clicks from the UPSs.

Some UPSs have the battery continuously as the primary source and at the same time the utility power, when on, is charging the battery. Should utility power be lost,there would be no audible click or measurable glitch.

Honestly, IMHO the computer should not crash if just one half cycle (8 milliseconds) or even two whole cycles (32 ms) are lost.
Old 12-06-23, 07:26 AM
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I used to do these tests on industrial equipment using specialized equipment. For those interested in the details:

IEC 61000-4-11 is an EMC test standard titled ‘Testing and measuring techniques – Voltage dips, short interruptions and voltage variations immunity tests’. It defines the setup, equipment requirements, and other conditions for testing systems to changes in the AC mains voltage. It is frequently used to show compliance. The standard describes three different tests:
1. Voltage dips are defined as sudden reduction in voltage to lower voltages for a short period of time, followed by recovery to the original voltage. Dips can last several hundred milliseconds.
2. Short interruptions are defined as a disappearance of AC voltage for a short period of time, typically not exceeding 1 minute, followed by recovery to the original voltage. Short interruptions can be considered as voltage dips to zero volts.
3. Voltage variations are gradual changes of the supply voltage to a higher or lower value than the rated voltage. The duration can be short or long.
Old 12-06-23, 11:23 AM
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Thanks guys for the helpful and detailed replies. I wouldn't be concerned, except the UPS clicking has only started about 2 weeks ago, they never did that before. I think I may try to get some kind of monitor like the Kill-a-watt and check things in multiple outlets in the house. Make sure it's not a single circuit having an issue. Thanks again.


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