ABSTRACT
This chapter gives an overview of modern industrial temperature sensors. It focuses on thermocouples and resistance devices, since they are used for more than 80% of temperature measurements in industry. Pyrometers and integrated circuits are gaining popularity. Some sensors for temperature monitoring are mentioned for completeness. Temperature is measured by its effect. Any object that has a property influenced by temperature is potentially a thermometer. The effect may be a change in the physical/chemical states of an object, dimensions, electrical properties, radiation properties, and others. The thermocouple, or thermoelectric thermometer, is probably the most versatile and inexpensive temperature sensor. There are three effects in a thermocouple circuit: the Seebeck, Peltier, and Thomson effects. Thermistors are available commercially in the form of beads, rods, flakes, and so on. A thermistor probe can be made very small, and its time constant comparable with that of a thermocouple, but much shorter than that of a resistance temperature detectors (RTD).
