P Floding;176991 Wrote: > Here are some pics. I noticed from your pics that the ground lead of the scope looks like a clip lead (though it's hard to tell). What I've found in measurements of mixed analog and digital systems (military applications) is that if you try to measure the noise in the analog section with a probe having a ground wire of just a couple of inches, you'll get greatly exaggerated pickup of digital noise. The cure is to use a probe that has two pins at the end. The first pin is of course the signal, and the second is a spring-loaded ground pin that sticks out a bit further than the signal pin. If you use such a probe, I think you'll find that your measurement shows considerably less pickup than what you get with a flying ground lead. I think the reason is that the loop formed by the ground lead causes pickup of magnetic fields from the digital circuitry such as clocks and other nasties.
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