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Originally Posted by e*clipse
I'd like to thank you for providing that example and reminder of why shielded analog inputs are important.  Sometimes it's a bit too easy to think "aww, that's not that important - it's just a matter of a few mV...." |
No problem ... I have a bad habit of using what is at hand instead of what I should be using.
We use a megger on motors to see if there are ground faults, resistance line to line to see if the phases are balanced - if the phases are shorted part-way through the resistance won't match ... that's about it. Once or twice we've checked insulation with a hi-pot. Sorry for the jargon - I can look up the *REAL* names of the instruments if you like
To measure small resistance on large motors we use a ducter. It is an ohm-meter that uses higher current to measure small resistance. 1 amps or 10 amps. The probes are sharp and there are two for + and two for -, so you get a reading on 'corrosion' as well.
The vendor that we use to rewind our motors uses this RLC type of equipment as well as partial-discharge .. a method of measuring insulation breakdown.
As I mentioned - our industrial controllers do their own tuning. It's a 5 minute process when we change a motor to tune to the new motor and away it goes. It just means I have to drive to site some evenings and weekends when motors fail in production ...
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Have you used anything like this at work? If so, any suggestions for what to look for in a good, affordable one?
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Nope