A position sensor is any device that permits position measurement. It can either be an absolute position sensor or a relative one (displacement sensor). Position sensors can be linear, angular, or multi-axis.
Some position sensors available today:
Capacitive transducerCapacitive displacement sensorEddy-current sensorUltrasonic sensorGrating sensorHall effect sensorInductive non-contact position sensorsLaser Doppler Vibrometer (optical)Linear variable differential transformer (LVDT)Multi-axis displacement transducerPhotodiode arrayPiezo-electric transducer (piezo-electric)PotentiometerProximity sensor (optical)Rotary encoder (angular)Seismic displacement pick-upString potentiometer (also known as string pot., string encoder, cable position transducer)