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Encoder technologies

In CAN-based control systems, in which something is rotationally moving, the position or angle is measured by means of sensors called absolute encoders.

NORMALLY, THE HOST CONTROLLER doesn’t need to calculate the position or angle. The absolute values provided by the encoder also avoid reference drives and re-calibration cycles. This means, after power-on the measurements are immediately valid. Encoders use optical or magnetic sensor elements. Optical sensors feature higher resolutions and accuracies. They are more robust against electromagnetic interferences. Magnetic sensors provide higher shock-resistance and can be packed even into IP69k-rated housings. They are more compact and more resistant against temperature changes. The price is also lower compared to optical encoders. Some encoders are able to calculate locally speed, acceleration, and jerk. Very important for the quality of encoders is the design of the ball bearing.

Camille Bauer (Switzerland) has released the Kinax WT707 sensor converting angular position of a shaft into a load independent position value. The CANopen connectable encoder is available in single- or multi-turn versions. Resolution and zero-point are programmable. The magnetic measuring principle guarantees minimal mechanical abrasion. The CiA 406 compliant encoder is optionally available in sea-water resistant enclosures.

Elcis (Italy) has introduced the 900 series of CANopen encoders. There are single- and multi-turn models available with resolution of up to 30-bit. The mechanic gear train transmits the movement of its master disc to a series of slave discs for shaft revolution counting. An electronic circuit cancels any mechanic backlash of the gear train. The absolute encoders are available in different IP66-rated enclosures.

Hengstler (Germany) offers the AR62/63 series of heavy-duty encoders. The products provide a single-turn resolution of 12 bit. The multi-turn versions feature a 12 x 16 bit resolution. The IP67- or IP69K-rated sensors are available with a 20-mm shaft. The housing diameter measures 58 mm. The maritime-approved (DNV) devices are 20-g vibration-resistant and 200-g shock-resistant. They operate contact-less, self-energetic, without battery, and no moving parts.

Ifm (Germany) has launched the RM6000 encoder using the Wiegand effect to keep the position values stored in case of a power failure and to pass the exact position without referencing. The 24-bit encoder is specified for temperatures between -40°C and +85°C. The housing is rated up to IP69K. The multi-turn sensor (4096 revolutions) features 4096 measuring untis per rotation. It also provides rotational speed measurements up to 6000 rotations/min. The CANopen interface is compliant to CiA 301 (version 4.02) and CiA 406 (version 3.1). EDS files (CiA 306 version 2.0) are available.

Pepperl + Fuchs (Germany) manufactures the CVM42H heavy-duty multi-turn encoder using magnetic sampling. The 30-g vibration-resistant and 300-g shock-resistant device provides a 24-bit resolution. It features CANopen connectivity and is suitable for temperature from -40°C to +85°C. The sensor is available in housings rated for IP66 to IP69K.

Posital (Germany) provides the MCD encoder family designed for heavy-duty vehicles. The magnetic position sensors use the Wiegand technology. They measure one revolution with a maximum resolution from 12 up to bit. The CANopen products come in a stainless steel housing. They are suitable for radial and axial shaft loads of up to 300 N. The shaft has a diameter of 42 mm.