Condet Proximity Switches

The new technology varies considerably from that used previously. It permits innovative proximity switches that have previously been inconceivable. The devices of the previous generation contain a front-mounted coil, which forms part of the oscillator circuit of a high-frequency oscillator. The coil produces a high-frequency magnetic field in front of the sensing face; conducting objects brought into this area increase the oscillator circuit losses, which are detected and evaluated by the built-in electronics. Unfortunately, the oscillating circuit is also affected by other, undesirable influences, in particular temperature and time dependent losses. As a result, the oscillator stability, and with it the achievable operating distance, are limited.

A new type of device, working essentially like a differential transformer, exhibits none of the above-mentioned disadvantages. This, however, has only been achieved at great technical expense, since at least two coils, an emitter and a receiver, have to be used. Today's most widely used device of this type even has three coils.