Introduction

Energy conversion components, as the name suggests, convert one form of energy into another, and those of interest for the purposes of this book convert other forms of energy either into electrical form or from that form. The importance of these components is that they allow electronic circuits to be used for detecting (sensing) and measuring other quantities such as acceleration, light flux and temperature, and they allow electronic circuits to form part of the control system for such quantities.

Conversion components are often classed as sensors or as transducers. The difference is often blurred, but in essence a sensor converts one form of energy into another with no regard to efficiency and is used for measurement purposes, and a transducer is used where the efficiency of transfer is more important, as in control systems or power generation. For example, a small anemometer propeller can sense wind speed, but a giant turbine with blades each weighing more than a ton each is needed to generate any useful power (at a cost in money and disruption that is quite disproportionate). For measurement purposes, the resolution of a sensor means the smallest change that can be measured for the detected quantity.

For any conversion component we can measure quantities that are termed responsivity and detectivity. The responsivity is a measure of the efficiency of the conversion and is defined as:

using whatever units are required for each form of energy. If the input signal and the...