The multiturn part operates with the same principle used in optical multiturn encoders; namely, gear reduction and permanent-magnet graduated disks. In contrast to electronic revolution counters, the mechanical gears do not need servicing and are not susceptible to interference signals and battery-buffer failure.

In contrast to optical encoders, the inductive version does not have an integral bearing. The encoder shaft is fixed to the motor shaft, and the encoder flange is secured directly to the motor flange. The air gap between the scanning PCBs is adjusted with simple tools during setup. Changes in the size of the air gap (e.g., from thermal expansion of the motor) influence the signal amplitudes. So developers took into consideration the tolerance for axial motion of the motor shaft; electronics corrects for any errors.

The encoder is also fairly robust. Typical motor applications need to survive 115°C. The encoder can run at up to 12,000 rpm, and take 100 g's of shock and 10 g's of vibration.

An EEPROM stores automatic commissioning data, with 1.4 kbytes of available memory. The motor-encoder unit receives an electronic ID label. The evaluation electronics of the encoder are also equipped with diagnostic functions which recognize and report malfunctions.

ENDAT EXPLAINED The EnDat (Encoder Data) interface is a bidirectional, pure binary serial interface. It's used to transmit position information from the encoder to the controller. Motor data such as voltage ratings, current ratings, and other details can store in the encoder memory. So on power up, the encoder dumps its memory to the controller. It also provides warnings and alarms for scheduled maintenance. EnDat contrasts with fieldbuses and standard point-to-point communications. A fieldbus, for instance, typically has slower transmission rates than point-to-point systems. A fieldbus connection with several sensors and actuators could take as long as several milliseconds for transmission, which could result in unacceptable dead times in the control loop. One solution is to use a faster fieldbus. But fieldbus-equipped encoders are more expensive than those without. Encoders with built-in fieldbus are best for applications with low-to-medium control dynamics requirements such as positioning accuracy, resolution, and transmission speeds, or where a fieldbus is already in place. Typical point-to-point configurations also have drawbacks such as low data transmission rates and low transmission reliability. There is also no support for automatic parameter input or safety monitoring and diagnostics. EnDat permits cable lengths of up to 150 m with maximum clock frequencies of 2 MHz. Redundancy techniques and simultaneous transmission of absolute and incremental position values makes encoders with an EnDat interface suitable for use in machines such as presses with critical safety requirements.

There are two tracks on the shielding disk. The single period track is used to determine absolute position values. The other track has 32 signal periods and is used to determine encoder accuracy.