-~- ~_vane ::y;) \ c:=::J ] 0=0 ] Dc:=JD Fig. 2. 39 Seven-segment devices for large displays and good visibility at up to 300 m can readily be obtained. Summary The number of transducer types is almost unlimited, and in order to bring our area of study down to a more manageable size we have considered transduc­ ers under four main headings. Input transducers for detecting mechanical change allow us to sense force, pressure, position, proximity, displacement, velocity, acceleration, vibration and shock in all their multiple manifestations. The basis of many mechanical sensors is the strain gauge which is usually used in a bridge configuration. Other devices such as the L VDT and synchro are also widely used. Temperature transducers form another large group, and we have looked at the operating principles of the major types, with some of the techniques used in compensating for non-ideal characteristics. Radiation and chemical sensing transducers form the remaining groups. Actuators rely almost entirely on electromagnetic action and, in modern equipment, occur most commonly as solenoids and relays, including the reed relay, and stepper motors. Visual displays also come in a bewildering range of types and sizes, but, because of their ease of interfacing with electronic circuitry, the majority are based on the LED and LCD. Review questions 1. What is meant by gauge factor? 2. Define Young's modulus. 3.

Inhalt

1 Principles of transduction.- Underlying physical principles of transducers.- Silicon technology.- Summary.- Review questions.- Further reading.- Problems.- 2 Sensors, actuators and displays.- Mechanical sensing.- The synchro.- Temperature sensing.- Radiation detection transducers.- Optical sensors.- Sonic transducers.- Nuclear radiation detectors.- Chemical activity.- Actuators, stepper motors and displays.- Summary.- Review questions.- Further reading.- Problems.- 3 Analogue processing of signals.- The ideal operational amplifier.- The practical operational amplifier.- Chopper stabilization.- Modulation.- The analogue multiplexer or scanner.- Summary.- Review questions.- Further reading.- Problems.- 4 Signal convertion.- The digital-to-analogue converter.- The analogue-to-digital converter.- Sample-and-hold circuits.- Voltage-to-frequency conversion.- Synchro-to-digital conversion.- The phase lock loop.- Summary.- Review questions.- Further reading.- Problems.- 5 Digital processing of signals.- Filtering in the digital domain.- Sampling.- Quantization.- Signal averaging.- Linerarization of sensor response.- Digital processing circuits.- The digital signal processor.- Summary.- Review questions.- Further reading.- 6 Interfacing.- Digital circuitry.- Specialized interfacing chips.- Transfers of data over greater distances.- Interfacing standards.- Summary.- Review questions.- Further reading.- Appendix A.- Solutions to problems.