Re: signal leads that pick up less ambient noise?

John Larkin <jjlarkin@highlandtechnology.com> writes:

I assume that your "leads" are a coax.

Yes, the loads something my co-worker threw together from old cable
laying around. One one side is BNC that plugs into the signal generator.
After than is a thin coax about 3mm thick. At the other end, he split
the inner conductor and the shield into two leads, one with a pin at the
end, and one with an alligator lead.

>
How are you measuring that noise? It's more likely to be ground loop
noise than coax shield leakage.

I have a project I'm doing building my own analog computer — which
currently does not have any filtering installed on it, other than some
100 nF bypass caps. I can see this heavy noise — about .6 mV p-p — on
all signal output, regardless of what op amp I tap into. If I remove the
analog computer and just tie the signal generator to the scope, I see
the same noise.

If I turn the computers off around my workbench, the noise becomes less,
proportional to the percentage of computers I turn off. If I take the
signal generator and the computer into another room with no computers,
the noise almost vanishes.

>
Common-mode chokes, ferrites or toroids, can help. Just plugging the
generator and the scope into the same outlet may help.
>

I am planning to go that route, with the chokes and such, once some
parts come in. But I was also wondering about the single leads
themselves, which feed from the signal generator into analog computer
inputs.

--
Christopher Howard