Electronics > Beginners
Oscilloscope Mains AC Sinewave Testing
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AndyC_772:
What's the frequency range over which you're really interested? Does that range actually pass through a mains step-down transformer? What does the gain-frequency response look like?

Personally I'd use an active differential probe with isolation and a known, reasonably flat frequency response.
EEEnthusiast:

--- Quote from: The Electrician on September 12, 2019, 04:41:37 pm ---
--- Quote from: scatterandfocus on September 12, 2019, 04:37:52 pm ---I'm interested in this topic too.  I tend to get some sporadic power noise in my audio recording chain.  Should it be ok to drop the voltage down to around 1V using a transformer and voltage divider and capture the output with a soundcard?

--- End quote ---

As long as the peak voltage applied to the sound card doesn't overload the card there should be no problem.  60 Hz is well within the usual audio band.  :)

--- End quote ---
Many audio codecs used on the sound cards have built in digital filters (notch filters) to filter out 50/60Hz. Most are enabled by default on the sound cards by the drivers. Some may even have ways to bypass the filtering with custom software. So, be aware of this one while capturing using the sound card.
richard.cs:
If you bought a transformer with a 230 V primary then running at 120 V it would have much lower core flux and be more linear - a good choice to use as an isolation transformer for mains monitoring.
scatterandfocus:

--- Quote from: EEEnthusiast on September 13, 2019, 10:13:14 am ---Many audio codecs used on the sound cards have built in digital filters (notch filters) to filter out 50/60Hz. Most are enabled by default on the sound cards by the drivers. Some may even have ways to bypass the filtering with custom software. So, be aware of this one while capturing using the sound card.

--- End quote ---

I never heard of that, and it may be the case for some onboard audio.  It definitely is not the case for standalone audio cards and audio interfaces.
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