ABSTRACT
A sensor, or instrument, is a device for measuring the magnitude of a physical variable. Sensors play an important role in the food industry. Sensors are the interface modules between the physical world and computers. Uncertainty analysis should be carried out in measuring a variable because the magnitude of an error is always uncertain. Transducers are devices that transform values of physical variables into equivalent electrical signals. This chapter discusses some of the basic transducers. A variable-resistance transducer converts either linear or angular displacement into an electric signal. A photoelectric transducer converts a light beam into an electric signal. A voltage is generated when light strikes the barrier between a transparent metal layer and a semiconductor material. A combination of light-transmitting optical fiber and miniature silicon sensors can be used to measure temperature, pressure, and refractive index. In the food industry, temperature is the most common physical parameter that must be measured.
