Absolute rotary encoder TWK

Ever since 1992 TWK encoders are being used for the pitch control of wind energy engines. The position of each rotor blade which has to be adjusted according to the wind intensity and the wind direction is monitored by an electro-optical absolute encoder. The device features a resolution of 12 bits and a serial SSI output interface. The specific item with a 65 mm diameter housing has been chosen with regard to the robust shaft and bearing construction to withstand axial and radial loads up to 250 N, for its IP 66 protection grade and with respect to the long life layout of the electronic circuitry.

A few years ago new electro-magnetic encoders have been developed. They operate with a small permanent magnet which activates an ASIC with integral Hall elements. Various digital and analogue output interfaces are available to comply with special requirements of the user. Several manufacturers of wind engines have already adapted this new type of encoder both with CANopen or voltage output interfaces.

In order to convert the movement of wind vanes into a proportional electrical signal the same electro-magnetic technique has been made available. Whilst the small magnet is directly connected to the shaft of the vane the sensor circuit and the conditioning electronics are settled on a circular pcb. As there is no friction the system works without wear and without any reverse action to the measurement signal. Technical report: PRA 0557).

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