On Thu, 09 Mar 2017 22:43:29 -0800, Robert Baer
wrote:

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.

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.




You just described that PCB trace current probe; just use known trace
length - with known width you get approximate current.

I do that. But multi-layer power pours are not such well-defined
resistors.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com