On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin
wrote:

On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
wrote:

https://www.sparkfun.com/products/11005

Replace the existing connector with a BNC, add a bit of series resistance
and you have a *very* cheap current probe for your scope.

I have a clamp-on ammeter that pretty much does that, although it just
indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
aren't terribly interesting.

My real problem with current measurement is DC, on PC boards. We want
to know how much current, say, an FPGA is using. Sometimes I include
current shunts in a layout, but sometimes I don't.

I generally use a ferrite (pi filter) on the supplies to uCs and DSPs
for EMI, then substitute a shunt to measure the power during test.

One can use existing switcher inductors as current shunts. I wish I
had a PCB trace current probe, but that's probably not posssible. You
can measure millivolt and microvolt drops across traces and vias.

The old HP current probe was a great debugging tool.