Cyberpower unit 90v output

E

EngrChris

Gawd
Joined
Dec 28, 2008
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I have cyberpower 900 watt UPS. When running on battery it only outputs 90 volts, why?
Edit, The unit is fairly new, just a few months.
 
How do you know it's actually putting out only 90V? Check it with a meter?
 
Than the UPS is bad. 90V isn't good for your electronics as they'll have to draw more current to function properly.
 
I just used a power-strip. I checked for ground and neural when switched off, The switch just disconnects the hot wire, so it should work for this test.

The multimeter still reads ~90-ish volts, could it be the simulated shinewave?
 
None of multimeters (even my older Fluke) have RMS.
Everything is cleared up with great tech support.
 
No, there's a difference between just straight AC measurement, and RMS. If you don't measure certain AC output with a meter that can perform RMS (or true RMS in some cases,) then your readings will be off. It's getting more common these days, but I honestly don't pay any attention - I have a Fluke with TrueRMS. It automatically determines based on sine whether it needs to do RMS.
 
AreEss said:
No, there's a difference between just straight AC measurement, and RMS. If you don't measure certain AC output with a meter that can perform RMS (or true RMS in some cases,) then your readings will be off. It's getting more common these days, but I honestly don't pay any attention - I have a Fluke with TrueRMS. It automatically determines based on sine whether it needs to do RMS.
Click to expand...

Truth.

Commercial AC in the US varies slightly in voltage but typically it is about 160V peak sine wave at 60Hz. BTW the frequency is usually bang on.

For a sine wave RMS the voltage is about .707 of the peak value - about 115V and average voltage is about 100V.

Most meters read average voltage/power and have a fudge factor built in to approximate RMS but it all depends of the quality and design of the meter.

True RMS reading meters usually divert a little of the voltage to heat an element and the rise in temp indicates the power and since the characteristics of the element are know the voltage can be calculated pretty accurately by the meter. As power is the "area under the curve" the type of waveform will affect the voltage reading.
The number sabove where off the top of my head and its an old head. Easily looked up online.

Bottom line the waveform and frequency and the type of meter all matter if you are trying to get a really accurate measurement. O-scope is the way to go to literaly "see" wth is going on.

An interesting note, long ago we had 120V (rms) house current, then 117 and now it is refered to as 115 or 110 and depending on demand can vary quite a bit.
 
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