Temperature Sensor

Temperature sensors convert real-world temperature values into proportional electrical signals for use in electronic control applications. For decades, these devices have been vital components within many types of process control and manufacturing systems, as well control systems for cars, aeroplanes and other applications. The rise of the IoT has brought many new applications, such as environmental monitoring.

In the earlier days of process control, a temperature sensor’s signal was typically fed to an analogue process control unit which in turn drove an actuator such as a valve or pump. Today, a temperature sensor output is usually digitised and connected, as one of many, to a PLC or industrial computer.

There are four common temperature sensor technologies:

  1. Resistance temperature detector (RTD), which tracks changing temperature with a correlated change in resistance value
  2. Thermocouples that comprise two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermoelectric effect produces a temperature-dependent voltage which can be interpreted to measure temperature.
  3. A Negative Temperature Coefficient (NTC) thermistor is a thermally sensitive resistor that exhibits a large, predictable, and precise change in resistance correlated to variations in temperature.
  4. Semiconductor-based temperature sensors can be implemented on integrated circuits. They comprise two identical diodes with temperature-sensitive voltage vs current characteristics that can be used to monitor changes in temperature.