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Encoders, Resolvers, Tach

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Testing a Resolver

You can test a resolver to see if it is indeed bad by using a voltmeter and measuring the resistance of the coils inside the resolver. The Resolver is constructed of three coils; two excitation coils and one reference coil that is connected to the axis controller card.

resolver

The image above shows the interface connector and the associated coil connections.

1) Check Resistance:

Harowe Resolver:

Pair A = 70 to 80 Ohms, Pair B = 190 to 220 Ohms, Pair C = 190 to 220 Ohms
Note: B and C will have the same values; the actual value depends on the manufacturer.

AMCI Resolver

Pair A = 35 to 45 Ohms, Pair B = 125 to 135 Ohms, Pair C = 125 to 135 Ohms
Note: B and C will have the same values; the actual value depends on the manufacturer.


2) Check for Coil-To-Coil shorts:
Any other pin combination besides the three individual pairs must result as an open circuit.

3) Check for Short to ground:
Check resistance of each pin to Resolver frame (case).  They must not be shorted to the resolver frame.

4) Check the voltage when connected:
Pair A = 1.7 VDC 
Pair B and C = 3.5 VDC
Pair A goes directly to the 1010 axis card; J2 bottom bullet connector.




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