Transformation of energy

What Are Temperature Sensors? Function and Types

What are temperature sensors? Function and types

A temperature sensor is a device that generally converts a temperature value into an electrical signal that can be read. It is also often referred to as a temperature probe or thermosensor.

Temperature sensors are used in places and in devices where temperature must be measured, in order to subsequently monitor or possibly regulate this temperature.

What Is a Temperature Sensor For?

Some examples where thermal sensors are used are:

  • Control of a solar hot water system.

  • Temperature control of photovoltaic panels to improve performance.

  • Food storage and preparation, refrigerators and freezers, and oven.

  • Medical uses: body temperature control , drug making, etc.

  • Industrial processes, especially those involving thermodynamic processes.

  • Regulation of air conditioners, heating and ventilation.

  • Heat engines : temperature sensors are used to monitor the coolant temperature and the temperature of the exhaust gases. Measurements are sent to the control unit for better engine performance.

What Types of Temperature Sensors Are There?

There are many types of temperature sensors. However, the most common sensors are the following:

  • Thermocouples. Thermocouples work by an electrical current between two different metals joined together that behave differently to changes in temperature.

  • Resistance thermometer. In this type of temperature sensors, resistors are used whose conductivity varies as a function of temperature. This variation allows to know the temperature of the material.

  • Electronic sensors. They work through electronic devices that generate a current or signal depending on the temperature.

The temperature sensors have the following appearance or construction variants adapted to your specific task and installation location. in this sense, we have the following types:

  • Immersion sensors: the measurement is carried out directly in the medium to be measured (water, oil, gas, air, etc.).

  • Cable sensors: they use a measuring element generally encased in a metal jacket at the end of a cable.

  • Application sensors: by indirectly derived temperature measurement outside of an application.

  • Clip-on pipe temperature sensors offer an indirect measurement of the temperature of a medium (water). They have the advantage that they are mounted outside of a pipe and cost savings. They are very easy to install.

What Is a Resistance Thermometer?

The resistance thermometer (resistance thermometer or RTD sensors) is a temperature sensor that exploits the variation in resistivity of some materials with the change in temperature. In particular, for metals there is a linear relationship that links the physical magnitude of a wire's resistivity with temperature. As the temperature increases the length of the resistance wire increases slightly.

There are types of resistance thermometers that can measure temperatures over a wide temperature range and above all have excellent linearity.

The TCR of such a sensor indicates the average change per degree centigrade of the resistance value. The measurement range is between 0 and 100 degrees Celsius. TCR stands for Temperature Coefficient of Resistance.

What Is a Thermocouple?

The thermocouple is a temperature sensor that is based on the Seebeck effect. The Seebeck effect is a thermoelectric effect by which, in a circuit formed by metallic conductors or semiconductors, a difference in temperature generates electricity.

Example of a thermocouple type temperature sensorThey can measure in a higher temperature range than RTD sensors.

The three most common types of thermocouples are type J, K and T calibrations. The most popular is the type K thermocouple due to its wide temperature range and low cost. However, the main limitation is precision; in fact, systematic errors of less than one degree Celsius are difficult to obtain.

Simply put, the thermocouple is made up of two conductors of known material that meet at a point called a "hot junction." Near this point the measurement is made. The other two ends are connected to a terminal board called the "cold junction", which is connected to the test tool directly or by an extension.

What Is the Engine Coolant Temperature Sensor?

The ECT sensor monitors the engine coolant temperature and informs the user of variations in it. Its main function is to prevent the engine from getting too hot and running better. 

Depending on the coolant temperature, the vehicle's computer adjusts the amount of fuel to be injected and decides to connect or disconnect the radiator fan.

If the engine is cold, an additional amount of gasoline must be injected to counteract the condensation losses.

If the sensor detects that the temperature exceeds a certain temperature range, the radiator fan will be activated. Its function is to prevent the engine from getting too hot.


Published: June 11, 2021
Last review: July 26, 2021