Inductive Proximity Switches as Encoders

Today, encoders are mature products, and are available in a variety of designs. However, compared to inductive proximity switches, they are significantly more expensive. In addition, they have rotating axes, and consequently require a certain care during assembly. Finally, encoders are often far too efficient for the requirements of the job to be done.

Substituting the encoder with an inductive proximity switch, which detects already present mechanical parts, such as a gear wheel, is a frequently used alternative. Where no suitable gear wheel is available, an additional one (or any suitably fabricated toothed disk) can be specially added. If need be, extra holes can be drilled in a co-rotating part, or a shaft with milled-on grooves, or equipped with spigots, can be used. In this way, a cheap, simple, and reliable substitute encoder is obtained. However, in practice, this solution often leads to difficulties, and the performance obtained is disappointing.