I'm thinking about methods to test a non-isolated homebrew 130W offline smps. I need to detect RF bursts "birdies", ringing, spikes and overshoots. An earth grounded scope will blow a fuse.
I'm trying out: Diode detector circuits with an analog meter. I suspect wrong readings from my digital DMM due to the HF. Also, it's only rated to 350Hz without true RMS. :( Just touching a pulse node with one probe scrambles the DMM display. (300Vpk square wave at 100khz.) I also get a nice hiss from my stereo speakers.
How about...a pick up "sniffer coil" on a scope probe. If that works?? Just a coil at the end of a scope probe. EMI is not such a bad thing... It's a test signal. :)
I have extra isolated windings on the power inductors. That's safe to earth ground for scope use..
I'll be interested in any nifty poorman test tricks... D from BC