On Thu, 14 Feb 2002, Alan B. Pearce wrote:

> >BUT, i have a 50Hz superimposed over my signal,
> >and showme not really what i expect
>
> This sounds as though the power supply to the circuit you were looking at is
> floating and not earthed. If you connected the scope probe ground lead to a
> ground terminal on the power supply (which seems likely from the way you
> write) then the power supply output probably is floating with respect to
> ground. Join the black and green terminal on the power supply together, and
> the hum signal should go away.

Along with all power on that circuit as the breaker pops with extreme
prejudice, if you're in the US where black is AC hot and green is ground.

Dale

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