Patent ID: 8111065

Claim:
A sensor unit for a rotary encoder which serves for detecting the rotary movements of a drive shaft ( 1 ) in both directions and which has a single-stage transmission with an input gear ( 15 ) which is arranged concentrically with respect to and is non-rotatably connected to the drive shaft ( 1 ), characterized in that the sensor unit ( 3 ) includes an absolute segment counter which serves for counting the angle segments through which the drive shaft ( 1 ) passes within each 360° rotation and has the following components: a magnetic segment counter exciter arrangement non-rotatably mounted on the second gear ( 16 ) of the transmission, that engages into the input gear ( 15 ), a stationary segment counter sensor arrangement which includes a Wiegand or pulse wire ( 28 ) with wound-on induction coil ( 29 ) and an additional sensor element ( 33 ) and which delivers electrical pulses whenever the magnetic segment counter exciter arrangement passes through predetermined angular positions, and an electronic circuit ( 32 ) which counts said electrical pulses, stores the respectively acquired count value and calculates therefrom the instantaneous angular position of the drive shaft ( 1 ) having regard to the transmission ratio of the transmission.