Sensor for ferrite piston position in neutral cylinder - detects field plate variation in impedance in magnetic field

摘要

The piston detecting appts. has two sensors placed in a magnetic field and fixed on the outside of the ferromagnetically neutral cylinder. When the ferrite piston reaches the sensor position the resulting field disturbance induces a sensor signal. The sensor is suitable for fitting to existing equipment at optional points on standard cylinders. It is small and responds reliably to pistons with high speeds. The sensor elements consist of two field plates placed one after the other in the direction of piston movement. They lie in the field of a permanent magnet and have equal impedance values when the piston is not near them. An evaluation circuit connected to the sensors detects the plate impedance variation caused by the magnetic field disturbance.