Introduction

Position sensors play an increasing role in our daily lives. They are abundant in our homes, in our cars, and in our work places. As sensing technology improves, positioning devices continue to get smaller, better and more inexpensive, opening the way for more applications than ever before.

As their name implies, position sensors provide position feedback. They are able to perform precise motion control, encoding and counting functions by determining the presence or absence of a target or by detecting its motion, speed, direction or distance. Position sensors detect a target object, a person, a substance or the disturbance of a magnetic or an electrical field and convert that physical parameter to an electrical output to indicate the target s position.

There are many ways to sense the position of a target. Some of them, such as limit switches and potentiometers, involve physical contact with the object being sensed. These are called contact position sensors. Contact position sensors often prove to be the simplest, lowest cost solution in applications where contact with the target is acceptable.

Sensor manufacturers have employed a much wider variety of approaches and technologies to develop non-contact position sensors, which have no physical contact with target objects and don t wear out from repeated contact. This chapter does not cover every possible technology that can be applied to sense position. The aim here is to provide a good understanding of the most...