A signal conditioner IC for inductive proximity sensors

In this paper, a monolithic signal conditioner for inductive proximity sensors (IPSs) is presented. It's based on the principle that change in inductance current slew rate at a constant voltage is related to inductance. Through detection of current slew rate slope di/dt, inductance can be detected. This method allows long distance between the conditioner circuits and the proximity sensor, which expands the sensors applications. The tested results show that cable length can be as long as 100m, with the change in proximity of triggering point no more than 0.4mm. The conditioner IC has been developed in a standard bipolar process technology with feature size of 6um. The chip area is 4.17mm×3.23mm. The total power dissipation is 48mW at power supply of 12V.