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Capacitive motor feedback systems from Sick

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article image Capacitive motor feedback system

Extreme ruggedness coupled with multiturn capability, an electronic type label and a HIPERFACE interface characterise the new SEK/SEL motor feedback systems from Sick .

With high precision, these absolute measurement systems serve as an alternative to resolver solutions used in industrial applications involving the detection of position and speed of rotation.

Capacitive motor feedback systems are available in four different versions: as the single-turn SEK37 and SEK52 or multiturn SEL37 and SEL52. The multiturn property of the SEL versions is achieved via a mechanical drive as well as magnets and Hall sensors.

A decisive advantage over resolvers is that the SEK/SEL units require no external evaluation because the electronics are all located on an ASIC integrated in the devices.

At the heart of the SEK/SEL series is the bearing-free capacitive sensor element, which is also economical compared to the resolver segment. The transmitter circuit board has a coarsely resolving disk track with three pulses per rotation and a finely resolving track with 16 pulses per rotation.

The receiver circuit board opposite has two conducting tracks, with which the coarse or fine pulses are detected. The pulses are generated or modulated by a star-shaped rotor whose rotation changes the dielectric between the transmitter and receiver circuit boards, whereby comprehensive or holistic scanning takes place so that neither radial, axial nor tilting tolerances during the rotation of the rotor can lead to impairment of the measurement accuracy.

The capacitive method of function is, however, precise and highly robust because it requires no ball bearings. These motor feedback systems also offer a level of temperature resistance that has hitherto largely been restricted to resolvers.

Regarding ruggedness and precision, the SEK/SEL devices offer the application-related performance features that are required in the lower segment of the industrial detection of position and speed of rotation, in particular. In automation terms, however, they offer users new possibilities, particularly those for whom aspects such as the multiturn feature or machine integration via the HIPERFACE interface standards are important.

The SEK/SEL motor feedback systems are thus suitable to two worlds of automation: the former world of the resolver, in which users require greater performance from the position-finder, and the “classic” motor feedback world, which can now exploit efficient temperature- and vibration-resistant devices without having to give up existing automation structures, such as those offered by SKS/SKM 36 or SRS/SRM 50 high-end motor feedback systems.

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