Rotary Sensor

FR sensor uses semiconductor MR element  (SMR) and permanent magnet. 
 It faces a gear which made of ferromagnetic material. 
 It outputs para-sine wave depending on a turn of a gear.
Strength of the FR sensor is not effected by  magnetic field and it can out put para-sine wave stably even though under such bad condition as cutting oil, dust and vibration.

Murata Icon X Series Lineup