Chapter 13 - Sensor technologies

Abstract

This chapter explains the different physical principles and technologies that are used in various types of measurement sensors. As well as summarizing the background theory, the different measurement sensors that use each principle are reviewed. The recent development of micro-electro-mechanical-systems (MEMS) devices and nano-electro-mechanical-system (NEMS) devices is also discussed in some detail. The chapter starts with a discussion on capacitive sensors and then moves on to resistive sensors. Following this, the various magnetic sensors in the form of variable-inductance, variable-reluctance, eddy-current, and hall-effect devices are reviewed. This is followed by three sections that cover piezoelectric transducers, strain gauges, and piezoresistive sensors, respectively. The next subject of discussion is optical sensors, which can exist in both open air-path and fiber-optic forms. In the case of the latter, both intrinsic and extrinsic fiber-optic sensors are discussed and the fundamental difference between the two types is explained. Following this, ultrasonic sensors are considered in both transit-time and Doppler-shift forms. Then, after a brief look at nuclear sensors, the chapter finishes with a discussion on microsensors (MEMS and NEMS devices).