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Absolute encoders

Absolute encoders for FAULHABER motors - extremely compact

In combination with the FAULHABER BL-motors, the absolute encoder is ideal for commutation, rotational speed control and position control. Absolute means that each shaft position within a revolution is assigned a unique angular value. Sine commutation is also possible with an absolute encoder.

Unlike the incremental encoder, an absolute encoder determines absolute positions, not relative positions. After switching on the absolute encoder, an absolute return value is available for each position of the motor shaft. A distinction is made between single turn and multi turn encoders. FAULHABER offers both single turn and multi turn encoders.

Selection of FAULHABER Absolute Encoders portfolio
Key Features
Signal output:
SSI Interface with BISS-C Protocol
Clock Frequency up to:
2 MHz
Output current up to:
4 mA
Operating temperature range:
-40 ... 100 °C
Minimal wiring requirements
Absolute angle information directly after power-on
No referencing necessary
Extremely compact
Line Driver

Absolute encoders from FAULHABER

Single turn or multi turn – Which absolute encoder is right?

The difference between the two absolute encoders is simple: with a single turn encoder, each position of the motor shaft corresponds to a specific return value. After a complete revolution of the motor shaft, the signals repeat. Thus, the single turn encoder supplies no absolute information about the number of completed revolutions. Positioning of more than one revolution is possible with this absolute encoder as well, however. Comparable to the incremental encoder, this is performed by counting the number of revolutions forward or backward using a counter on the motor control. For travel distances of more than one motor revolution, it is necessary to reference after a power interruption. No referencing is necessary for travel distances of less than one motor revolution.

Multi turn encoders behave differently. This type of absolute encoder also records the number of completed revolutions. This is performed either by means of an additional sensor as well as an electronic memory element or by means of a gearhead. Thus, multi turn encoders supply an absolute value over multiple revolutions of the motor shaft. This can be recorded within a defined number of revolutions, which are limited by the memory element or gearhead. Referencing is generally not necessary if the maximum amount of revolutions is not exceeded.

Data transfer to BISS-C

The resolution of an absolute encoder is defined via the number of steps per revolution and is specified in bits. Absolute encoders generate a serial code from multiple bits. FAULHABER absolute encoders support the SSI Interface with BISS-C Protocol. BISS-C supports communication with clock speeds of up to 2 MHz. Here, the absolute position value (DATA) is transferred in synch with a cycle (CLK) specified by the controller.

Functionality of absolute encoders

Absolute encoders of the AES-4096 LAESM-4096 and AEMT-12/16 L series consist of a diametrically magnetized, two-pole sensor magnet which is fastened to the motor shaft. A special angle sensor for detecting the motor shaft position is positioned in an axial direction in relation to the sensor magnet. The angle sensor comprises all necessary functions, such as Hall sensors, an interpolator and driver stages. The analog signal of the sensor magnet detected by the Hall sensors is processed, after appropriate amplification, by a special algorithm to produce a high-resolution encoder signal. At the output, all FAULHABER absolute encoders provide absolute angle information within one revolution at a resolution of 4096 steps per revolution. Furthermore, the AEMT-12/16 L multiturn absolute encoder delivers a multiturn resolution of 16 bits. All FAULHABER absolute encoders feature an SSI interface with BISS-C protocol.

The absolute encoder is ideal for commutation, rotational speed control and position control. In our Drive Calculator, you can find the combination of FAULHABER absolute encoders and FAULHABER motors that ideally suits your requirements.

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