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When dealing with systems where the temperature must be measured, one will have several choices for sensors. Let's say that one needs a temperature sensor that produces a voltage and needs to measure temperatures between 75° and 600°. Then your choice would be a thermocouple. If the sensor signal needed to produce a change of resistance, then the choice would be a resistive temperature detector (RTD) or a thermistor. If the sensor signal needed to produce a proportional current, then the choice would be a solid-state temperature sensor.
One can begin to see that each of the sensors provides a different type of output signal that will be compatible with the control circuit one is using. In addition, each type of sensor will have specific temperature ranges that it can operate in, which will also help to narrow down the choice. The remainder of this section will explain the operation of each type of sensor in greater detail.
