Electronics > Metrology

Nice little Milliohm Meter over at Circuit Cellar

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For those of you who  you haven't seen it yet, there is a nice DIY milliohm meter article in the Sept 2016 issue Circuit Cellar.  Worst case error budget is around ~0.5%, which really isn't too bad for an inexpensive milliohm meter.  Accuracy drops off at the low end of range, as is usual - but at a few mOhm's it becomes difficult to attach leads to just about anything for a repeatable measure.

My suggestion when using this circuit on lowest end of range is to add a known accurate 50 or 100 mOhm into your circuit and then take your measure from that known offset. 

Handy for tracing out shorts and bad bypass caps too.

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Thanks for that link, I will look into it tonight.

Very nice. The idea of driving the "force" leads by sharing current between several IOs is clever.

It might be built with a greater accuracy ADC (MCP3553, LTC2440...), requiring only some minor adjustments in software, to achieve even lower noise.



Offset compensation? If not, source(s) of error are large when measuring low ohms.


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