[RFI] RFI clip-on probe?

[Cortland Richmond]

You can make a tolerable clip-on probe by putting a one-turn (preferably
shielded) 
pickup winding through a snap-on ferrite bead. You could choose a bead to
not 
adversely affect current in the lead it's on (less than 5 ohms) or don't
worry about 
it if you only need relative readings or pickup for an already undesired
signal.

You can discriminate between common-mode and differential mode noise, too.
Running 
both sampled conductors through the core in the same direction couples
common-mode 
to the pickup loop, and cancels differential. Splitting the pair, and
running the 
wires through the core in OPPOSITE directions, cancels common-mode, and
couples 
differential mode noise. This is often useful troubleshooting, and though
not my 
invention, as it is widely used by EMC engineers, may appear as part of my 
contribution to one of Mark Montrose's books soon.

Cortland

> [Original Message]
> From: Wiley Sanders <wsanders at wsanders.net>

> Sounds neat - how is the probe constructed? Do you make a loop around the 
> conductor, similar to the high-amp AC ammeters except with a loop or two
of wire?