Absolute Position Encoder
An absolute encoder is a measuring element that produces a unique value for every angle and that knows the position without performing a homing movement when the power is cut and restored. Unlike an incremental encoder it does not count pulses. In a 12-bit absolute encoder one turn is represented as 4096 distinct position values.
An incremental encoder only reports the change; when the system is switched on it does not know the position and has to reference itself by going to a limit switch. An absolute encoder reads the real position directly at power-up.
- The practical result is knowing where the actuator is after a power interruption and carrying on working without making an unnecessary movement.
- It is also safer in a vibrating environment: there is no such thing as losing count, missed pulses do not accumulate.
On the GS740-3P the position feedback is taken with the AS5600 and this measurement is absolute. Even so, the upper limit information from the installation is a separate matter: which angle value is to be considered "full throttle" is taught with the blue wire trigger and held in memory. When the cable slips or is replaced this match is broken; the encoder keeps reading the angle correctly but the throttle position it corresponds to has changed. That is why the calibration is repeated.
Context in which this term is used: Electronic speed and throttle control on a diesel engine