Brag: Scope probes

From: Dave Brown <tractorb_at_ihug.co.nz>
Date: Sat Dec 21 05:15:00 2002

----- Original Message -----
From: "R. D. Davis" <rdd_at_rddavis.org>
> Why not just connect a test lead with banana plug at the 'scope end,
> an an alligator clip on the other end, to the ground connector on the
> 'scope and use that? Works for me. I've always found the ground
> leads attached to probes of 'scopes to be too short and useless
> anyway... not really worth bothering with. Alternately, can't you
> just solder a wire, with an alligator clip on the other end, to the
> 'scope's probe? None of my 'scope probes have ground wires, other
> than the cable shielding, connected to them, and this has resulted in
> no problems during the past couple of decades.
>
> Is there something that I'm overlooking?

 Surely is--
 It's called lead inductance, and when you look at waveforms containing
frequencies above just a few MHz, using that long earth lead instead of the
correct short probe one, what you see on the scope will be way off what
things really look like! The difference will get worse at higher
frequencies.

Dave B
Christchurch, NZ
Received on Sat Dec 21 2002 - 05:15:00 GMT