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I recently bought a basic digital oscilloscope and wanted to power my oscilloscope from 600VA computer UPS.

I have two questions:

  1. Can the UPS give isolation from main supply? (As an alternative to an isolation transformer.)

  2. The output of the computer UPS waveform is "simulated sine wave." Will it affect the performance of the oscilloscope?

UPS datasheet

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    \$\begingroup\$ You should not be floating your scope. Float your device under test, not your scope. Floating your scope makes things like all the BNC exposed connectors, probe ground clips, and the voltages right behind the knobs and buttons on your scope float all the way up to whatever you are testing which is dangerous. \$\endgroup\$
    – DKNguyen
    Jul 2, 2019 at 4:58
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    \$\begingroup\$ First, although most power supplies are not officially certified to use with modified sine wave as power source, but often the majority of switched-mode PSU should work without problems, including oscilloscopes, so yes, you can use a UPS to provide backup power to your scope. Next, if you UNPLUG your UPS and run it on batteries, the inverter is no longer ground-referenced, and it does provide isolation in a sense, but it's dangerous and YOU SHOULDN'T DO IT, see electronics.stackexchange.com/questions/73991/… \$\endgroup\$
    – 比尔盖子
    Jul 2, 2019 at 5:30
  • \$\begingroup\$ after long surfing about powering oscilloscope, i wrongly understand to isolate oscilloscope instead of testing unit, thank you all \$\endgroup\$
    – masternone
    Jul 2, 2019 at 6:35

3 Answers 3

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1- does computer UPS give isolation from main supply? ( like alternative to isolation transformer)

No, "UPS 600VA" it is not isolating from main supply

2- output of the computer UPS waveform is "simulated sine wave", does if affect performance of oscilloscope

No it doesn't affect the performance because it converts to DC inside the oscilloscope.

A simulated sinewave is basically a pulse width modulated squarewave, with a proper output and/or input filter i would not expect any issues.

shall i use computer UPS for oscilloscope

No, I don't see any reason for this unless you live in a place with a lot of short-term power outages.

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  • \$\begingroup\$ A UPS could be used to provide isolation from the supply. Plug in the UPS for a few hours to charge the battery inside. Then unplug it from the supply, and plug the oscilloscope in to the UPS. \$\endgroup\$
    – Simon B
    Jul 2, 2019 at 9:45
  • \$\begingroup\$ I think you are wrong. When you unplug UPS from the mains it is pretty much isolated from the mains. \$\endgroup\$
    – Chupacabras
    Jul 2, 2019 at 11:47
  • \$\begingroup\$ This is not the purpose of a UPS @Chupacabras Never float a oscilloscope: electronics.stackexchange.com/questions/73991/… \$\endgroup\$
    – Daniel K
    Jul 2, 2019 at 13:22
  • \$\begingroup\$ I didn't say it is a purpose of any UPS. I just commented on your statement which is false. Oscilloscope connected to UPS (which is disconnected from the mains) is isolated from mains. No matter whether it is recommended or not. \$\endgroup\$
    – Chupacabras
    Jul 2, 2019 at 14:42
  • \$\begingroup\$ For sure it is isolated but nobody will operate an oscilloscope like that. Therefore I did not consider this case. \$\endgroup\$
    – Daniel K
    Jul 2, 2019 at 15:53
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I've seen quite a few pieces of test equipment used for years on a UPS. Including oscilloscopes. As far as I know, there hasn't been any issues. The ground passes through the UPS so the test equipment is still at earth ground. Sometimes the neutral passes through only when the UPS is powered from the mains, but sometimes it is isolated through a transformer.

I myself have a whole house battery backup system and many times the power has been out when I've been working on something, and I never knew. It is a very pure sine wave.

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Can the UPS give isolation from main supply? (As an alternative to an isolation transformer.)

Only if the UPS provides isolation (and it would have an isolation barrier internally) Some UPS's convert AC to DC and then back to AC with switchers.

The output of the computer UPS waveform is "simulated sine wave." Will it affect the performance of the oscilloscope?

It really depends on the setup, but if the ground of the oscilloscope is isolated from earth, then it's most likely floating. Whatever your measuring would need to be plugged into the UPS or there really wouldn't be a reference for the oscilloscope ground.

Whatever your measuring also needs to be grounded to the oscilloscope.

This is also not a good way to measure any high voltages because the ground of the oscilloscope would need to be connected to the high voltage device and that could create a saftey hazard.

The best way to make isolated measurements is with a differential probe because it has two terminals and determines the voltage between them

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