On Sun, 5 Mar 2017 16:18:50 -0000 (UTC), Cursitor Doom
wrote:

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

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.

Indeed they're not. But your meter is presumably *only* designed for use
at 60Hz, I would imagine. Hook it up to a 100Hz signal and you'll see
nothing at all in all probability. ;-)

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.

Do they even exist? That would be amazing but no doubt *way* beyond what
I can justify to splash out on as a mere hobbyist.


A 1" long, 20 mil wide 1oz trace will be about 25 milliohms. 1 amp
makes 25 millivolts, and lots of cheapish DVMs will resolve that well
enough. You probably need a bench DVM with microvolt resolution to
measure, say, 1 amp running through a via, but you could build a
little microvolt meter or amp pretty easily. PCB trace and via
resistances need to be calibrated, which is only a minor nuisance.

Here are some pcb-trace shunts, down near the connector:

https://dl.dropboxusercontent.com/u/...ower_Board.JPG

One of the great mysteries of electronics is "where is the current
going?" Sometimes a thermal imager helps figure that out. A little
magnetometer would be fun, not hard to do these days.




--

John Larkin Highland Technology, Inc

lunatic fringe electronics