Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
kinda depends upon the purpose to which the power supply is intended -- there is a real, real, real guru amongst the denizen of DIYAUDIOr's and that's janneman
but here's a start -- use a capacitatively coupled differential amplifier for the input -- for those measuring power supply noise where a precise ADC measurement is required you want to filter the supply over a 100 milliHertz to 10 Hertz bandwidth for a period of 10 seconds. take a look at the materials on Texas Instruments website for their TL431 shunt regulator for a circuit --
Jim Williams application notes at Linear Technology also have some really excellent suggestions. I guess if you have a really good scope you could look at the envelope over a 10 second interval.