Publisher Summary
This chapter discusses the various segments of sensor technologies. Capacitive sensors consist of two parallel metal plates in which the dielectric between the plates is either air or some other medium. Magnetic sensors utilize the magnetic phenomena of inductance, reluctance, and eddy currents to indicate the value of the measured quantity, which is usually some form of displacement. Hall-effect sensor is a device used to measure the magnitude of a magnetic field. Piezoelectric transducers produce an output voltage when force is applied. Strain gauges are devices that experience a change in resistance when they are stretched or strained. Piezoresistive sensor is made from semiconductor material in which a p-type region has been diffused into an n-type base. Optical sensors are based on the modulation of light travelling between a light source and a light detector. The chapter states that ultrasonic devices are used in many fields of measurement, particularly for measuring fluid flow rates, liquid levels, and translational displacements. The best measurement resolution that can be obtained with an ultrasonic ranging system is equal to the wavelength of the transmitted wave. Signal levels at the output of ultrasonic measurement systems are usually of low amplitude, and are therefore prone to contamination by electromagnetic noise. The main applications of ultrasound in imaging are found in medical diagnosis and in industrial testing procedures. Nuclear sensors are uncommon measurement devices, partly because of the strict safety regulations that govern their use, and partly because they are usually expensive.