TABLE OF CONTENTS Mike Tooley
Sensors provide us with a means of generating signals that can be used as inputs to electronic circuits. The things that we might want to sense include physical parameters such as temperature, light level, and pressure. Being able to generate an electrical signal that accurately represents these quantities allows us not only to measure and record these values but also to control them.
Sensors are, in fact, a subset of a larger family of devices known as transducers so we will consider these before we look at sensors and how we condition the signals that they produce in greater detail. We begin, however, with a brief introduction to the instrumentation and control systems in which sensors, transducers, and signal conditioning circuits are used
Figure 21.1 shows the arrangement of an instrumentation system. The physical quantity to be measured (e.g., temperature) acts upon a sensor that produces an electrical output signal. This signal is an electrical analog of the physical input but note that there may not be a linear relationship between the physical quantity and its electrical equivalent. Because of this and since the output produced by the sensor may be small or may suffer from the presence of noise (i.e., unwanted signals) further signal conditioning will be required before the signal will be at an acceptable level and in an acceptable form for signal processing, display and recording. Furthermore, because the signal processing may use digital rather than analog signals an...
