Measuring armatures
 

Please advise on what is the best way to measure if an armature is 12 turn during an event.

The reason for this is to apply a rule of 12 turn motor limit and I need a valid, consistant and accurate way of measurement.

Thanks.

Disassembly (destroying the arm) aside, I know you can use a voltmeter and measure resistance in the wiring, but I am unsure of the exact measurements.....

with an LCR meter.

To further explain Nuno's comment...

A arm of a specific wind will have some measureable 'Inductance' as well as 'resistance' and I supose even some 'capacitance'...

The resistance is what a Ohm meter can measure, however the resistance of the windings of a armature is so small, that most Ohm meters won't accurately measure it... or not accuately enough to determin if the arm is legal...

Typcialy the best electrical measurement would be the 'inductance', and a LCR meter would be used to measure this... Again, the differaance in the inudutance measurement is going to be realitively difficult to measure but there are meters that are afordable (less then $250) that can do it pretty well...

I beleive what typicaly gets done is that a known good arm is measured for Inductance, then all other arms at that perticular race must be very close to that measurement... This sort of gets around a issue of each meter might read slightly differnt and/or would require some calibration to insure better accuracy.

well said, that's how in Europe with the 12 turn rule the motors are checked.