Inductive proximity sensor with a flat coil and a new differential relaxation oscillator

摘要

A high-sensitivity fiat-coil inductive proximity sensor microsystem has been realized and successfully tested. The fiat coil, made with CMOS-compatible post processes, is connected to a versatile differential relaxation oscillator electronic interface. In this new and simple interface, the excitation, the signal extraction and amplification are assured by only one operational amplifier. Experimental result on the microsystem confirm that large output frequency variations occur when a metallic target approaches the sensor.