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SICK Stegmann has introduced its SEK/SEL37 capacitive motor feedback systems.

The systems are 36mm (d) with Hiperface interface and are available in singleturn and multiturn versions with a radial or axial plug outlet.

Operation requires no ball bearings and offers temperature resistance previously only found in resolvers.

SEK/SEL37 systems are designed for mounting directly onto tapered shafts.

Holistic scanning compensates for eccentricity errors, with possible error sources having been practically eliminated by removing wear and tear parts.

The SEK/SEL37 provides 16 sine/cosine periods, resolution of 512 steps per revolution, and one (singleturn) or 4096 (multiturn) steps per rev.

They are rated for shock resistance to 100g/10ms, vibration resistance to 50g/10 to 2000 Hz, and provide reliable operation in temperatures ranging from -40 to 115C (singleturn) or -20 to 115C (multiturn).

SEK/SEL37 capacitive motor feedback systems are a suitable alternative in applications currently using resolvers, but where users need higher-performance final positioning such as servo motors, handling drives, feed-axis or standard robot applications.

They are also suited to use in traditional motor feedback applications that demand higher-than-normal robustness for reliable operation in high-temperature and vibration environments.

Impulses are generated by a star-shaped rotor that changes, through its rotation, the dielectric material between the sender and receiver PCBs.

The holistic scanning process means that neither radial nor axial tolerances introduced during rotor rotation can impair the accuracy of measurement.

The multiturn properties of the SEL versions are implemented using a mechanical gearbox in combination with magnets and Hall sensors, achieving absolute, non-volatile code and position determination.

An advantage over resolvers is that no external evaluation unit is required as all electronics are contained within an integrated ASIC.

Due to Hiperface, all popular servodrives have an interface standard that covers all applications needing only one type of signal line.

Another advantage is the possibility of self-initialisation and automatic controller parametrisation of the drive system by using an electronic-type label, as with the SEK/SEL motor feedback systems.

Motor characteristics, serial and part numbers as well as further data which help in case of service or exchange are written here and can be used to independently adjust the controller to the parameters of the motor.

Hiperface is an eight-wire interface standard that makes it possible to get commutation, speed regulation and position information from a single device.

The physical interface includes two wires for an RS485 link, four wires for sine and cosine signals and two wires for the power supply; a reduction from as many as 19 leads in a traditional system.

Hiperface-compatible motor feedback systems combine the functions of both incremental and absolute encoders.

The absolute value in these systems is calculated when the device is initially turned on, and is then transmitted via the RS-485 interface to a counter in the drive.

The drive uses this initial absolute value for the commutation of the motor and also as a pointer to identify the exact period of the sine/cosine signals that the drive is currently evaluating.

The drive then increases the base resolution of the sine/cosine signal by interpolating these signals in the drive with an A/D converter.

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