I'll assume you're interested in audio band noise since the RF stuff is pretty easy to filter off. A lot of high performance noise measurement equipment of course has some sort of numerical readout, but also has a speaker for easy relative noise level and frequency detection. You could get a small toroid with a 12V secondary and run it to the full range speaker of your choice through a 12dB passive high pass centered around 100 to 120 Hz. That will let you hear how dirty your line is pretty easily.
You can send that output to your scope or sound card and run an FFT on it if you want. The 60Hz will be strongly attenuated, but you know that's there at full power. You'd only have to be sure that the crossover was properly terminated if you disconnected or padded the speaker.
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Hello
I know that there is power line sniffer noise Detector sold on the market, they have a small meter.
I was thinking of a small isolation transfo and a 100 hz high pass filter with an op-amp to amplify the noises and a small meter, but I was not sure how to implement it.
Thank
Bye
Gaetan
I know that there is power line sniffer noise Detector sold on the market, they have a small meter.
I was thinking of a small isolation transfo and a 100 hz high pass filter with an op-amp to amplify the noises and a small meter, but I was not sure how to implement it.
Thank
Bye
Gaetan
I have some #36 enamelled wire wound around a ferrite rod and it feeds into a wideband amplifier -- generic audio grade opamp is useless for this operation -- some of the stuff you want to see is in the 100's of kHz --
I've seen the Monster power line filter demo box at The Source. It's a 3-1/2 digit AC voltmeter, speaker and gain control.
You get to listen to before/after a cellphone charger (small switching power supply) is plugged in, and before/after their line filter.
It acts like a low-pass filter running to an LM386 audio amp and AC Voltmeter. So it shows noise up to maybe 50kHz? The displayed numbers are arbitrary, depending on the volume setting.
What frequency range are you interested in? I (carefully) use a scope with an RF probe, looking at 100kHz-1MHZ up. Using an isolation transformer attenuates these frequencies and you don't get many fish.
You get to listen to before/after a cellphone charger (small switching power supply) is plugged in, and before/after their line filter.
It acts like a low-pass filter running to an LM386 audio amp and AC Voltmeter. So it shows noise up to maybe 50kHz? The displayed numbers are arbitrary, depending on the volume setting.
What frequency range are you interested in? I (carefully) use a scope with an RF probe, looking at 100kHz-1MHZ up. Using an isolation transformer attenuates these frequencies and you don't get many fish.
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