These transfer their information to the control electronics in serial data stream. Serial data provides transmission of the data one bit after the other instead all at once. Serial Encoders are checked by a computerized serial interface, accurate count checks are done with special Pulse Counting Gadgets. The serial encoder is similar to the incremental encoder except that it has additional processing electronics built in that process the information to the control.
Hall Effect Switches - are solid state devices that will output a voltage when it is placed in a magnetic field. The output will change once the magnetic field is reversed. Sensors are used to return a signal that corresponds to the position of the permanent magnet rotor. If Hall Effect Switches are positioned close to the rotor, then signal from the sensors will represent the position of the rotor's magnets. A majority of Hall Effect Switches provide and open collector or open drain type of an output. The switch acts as a ground and typically does not output any voltage. To have a useful output signal a pull-up resistor must be added.
Resolver - A Resolver is a rotating transformer, located on the motor shaft. It does not include bearings and is typically used in dirty, oily applications. Resolvers may be excited at operating frequency; the sine and cosine outputs may be looked at on an oscilloscope or other testing device for proper levels and change rotation. Resolvers are electro-mechanical devices, the resistance of the windings and the insulation of the winding to the ground should be checked when checking for repairs. Axxa rewinds Resolvers when needed necessary and teststhese with full speed at any frequency.
Tachometer - provides running speed and feedback. All Tachometers are tested by voltage output per the preset RPM's, polarity and are tested with its servo motor. If the Tachometer cannot be tested before the servo motor was dismantled, then a variable speed tachometer is checked on a test stand.
Axxatests waveforms and makes measurements with Specialized Gadgets. Our feedback; servo encoder repair, servo resolver repair and servo tach repair involve:
- disassembly and cleaning encoder optics
- detection of signal distortions, sin/cos, TTL, EnDat, BISS, SSI
- setting proper signal amplitude
- positioning optics
- correcting signal phase shift
- replacing measurement system bearing
- regeneration of peeled-off rotary encoder disk
- setting absolute positions of encoders and resolvers (commutation)
- preparing customized encoder cables for client’s machine
- replacing brushes in tacho
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.