Analog measurement (SIN/COS track)

Analog encoder systems provide sine and cosine signals, which are output as difference signals.
The position of the rotor cannot be uniquely determined with a single sine signal. Two sensors, electrically offset by 90° are used that generate a sine and a cosine signal. Through evaluation of both signals, the rotor position and direction of rotation can be uniquely determined.

 

If an encoder provides exactly 1 SIN/COS period per revolution (e.g. resolver), the position within a revolution can be determined absolutely (single turn absolute encoder).

If there are several SIN/COS periods per revolution (e.g. I-encoder), only a relative movement of the rotor can be determined. (Incremental evaluation)
For position control over more than one SIN/COS period, the position reference between the rotor position and machine must be created by the user with a homing cycle. To do this, these encoders have a homing pulse that, together with a cam signal at the machine, defines the machine zero point in the homing cycle. After the homing cycle, the actual position value is continuously determined in the drive controller with the SIN/COS tracks.

 

For correct commutation in synchronous motors, the resolver must be tuned after assembly to the motor shaft.The commutation offset determined in encoder tuning is stored in the parameter record (ID32959 'Offset resolver').