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piclist-bounces@mit.edu wrote:
> Or - toroid, single transistor amp, comparator and an
> integrator?  Use a ratio on the toroid to get enough
> sensitivity for a minimum current?


years ago I used a toroidal current transformer for something similar. It was a Bicron EX9PC200 (I'm sure there are others, that's just the one I happened to find at the time). Wind a turn from the AC hot through the toroid, select an appropriate bias resistor, and it gives you a voltage out proprotional to current drawn from the AC source.

The trick would be selecting a combination that lets you reliably detect the entire anticipated current range. It might take two current transformers, one for low ranges, one for higher ranges. Or maybe an op-amp to amplify the low-range into useable results (and also limit the high range) could suffice, especially if you just have to detect if something is drawing power or not. You'll have to determine if this approach is suitable for you, but it sounds feasible. 

Production environment i take to mean "use it on a shop floor," in which case cheap should be replaced by reliable. 



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