Re: [sdiy] PSU ripple/hum testing

[Roman]

poking around with cable to audio amplifier is how I 'measure' power supply ripple. For 200uV you definitely need an amplifier.
Add protecting reverse parallel diodes at amplifiers input, and limiting diodes at output (reverse parallel too). This way you can set your measuring amplifier to gain of 100 and still be sure it doesn't go up in smoke and doesn't generate signals higher than +/-0.7V, safe to plug into audio amplifier then.

Roman

---- Wiadomość Oryginalna ----
Od: Lincoln Fong <Linc at christeld.freeserve.co.uk>
Do: Synth-Diy <synth-diy at dropmix.xs4all.nl>
Data: Thu, 18 Sep 2003 09:48:13 +0100
Temat: [sdiy] PSU ripple/hum testing

>Good to be back after a long period of silence.
>
>Does anyone have a good way of testing for PSU ripple? I have some PSUs
>(11 of them!) that can deliver 10 amps at +/- 15V and 30 amps at 5V. The
>ripple under load is meant to be less than about 200 uV but my (not very
>good) scope only goes down to 10mV per division. I was thinking I could
>maybe build a small amplifier with DC input filter and 'listen' to the
>ripple, maybe with a few calibrated LEDs as I would like to be able to
>'poke around' inside my huge old mixing board and PSU rack. The initial
>spike when attaching the probe could kill my amp/speaker/ears though.
>Any ideas or should I get a better scope?
>
>Thanks,
>
>Lincoln
>
>_________________________
>Lincoln Fong
>http://www.fongelectronic.com
>
>