All Tachometers are tested by voltage output per the preset RPM's, polarity and will have neutral tested with its servo motor. If the Tachometer could not be tested before the servo motor was dismantled, then we use a variable speed tachometer test stand. The thermal relays are then checked with an ohmmeter.
Tachometer output and waveform are checked for proper operation. The output value compared to the rate output at the test speed. The ripple contact of a DC tachometer is checked with an oscilloscope. This will indicate the condition of the Tachometer's commutator, brushes and windings. If the output is from an AC Tachometer then the waveform and time with the hall sensors will be checked.
We Tests waveforms and makes measurements with the Mitchell Electronic Feedback Signal Breakout Box. The breakout box looks for various feedback and counter generated voltages. The typical test points the motor line to line, motor line to neutral, tachometer signals, encoder signals, resolver signals and commutation signals.