TABLE OF CONTENTS New applications that have demanded low-cost sensors for providing measurements of acceleration and angular motion have provided a major incentive for the development of micro-machined electromechanical system (MEMS) sensors. One typical modern application is the use of inertial sensors in transport, such as motor cars; an indication of the current extent of the use of these devices in this application and examples of many others are given in Chapter 15.
MEMS devices are one of the most exciting developments in inertial sensors in the last 25 years. These devices overcome many of the features that have impeded the adoption of inertial systems by many potential applications, especially where cost, size and power consumption have been governing parameters. Many efforts involving value engineering and automation have been applied to the design and manufacture of conventional inertial instruments, with significant success; however, the cost has remained high. The major reasons centre on:
high parts count;
requirement for many parts with high-precision tolerances;
intricate and precision assembly techniques;
accurate testing, characterisation and calibration.
The use of silicon as the base material in the manufacture of the components offers a radical approach and overcomes many of the issues considered above for conventional mechanical sensors. This is summarised in Figure 7.1. Additionally, they can be considered as offering a sensing device on a chip with the very real prospect of a precision inertial measurement unit sensor on a chip in the near future. This holds the opportunity to make an inertial navigation system...
