What is a Temperature Sensor?

A temperature sensor is a device used to measure temperature. This can be air temperature, liquid temperature or the temperature of solid matter.

There are different types of temperature sensors available and they each use different technologies and principles to take the temperature measurement.

Different Types of Temperature Sensor

Thermistors can be very small in size. They consist of a sensing element which can be either glass or epoxy coated and have 2 wires so they can be connected to an electric circuit. They measure temperature by measuring the change in resistance of the electric current. Thermistors are available as either NTC or PTC and are often low cost.

RTDs or Resistance Temperature Detectors work in a similar way to Thermistors and measure ohmic resistance to measure temperature. They are connected to a circuit in a similar way to a thermistor but they have a much wider temperature range and can measure extreme temperatures.

Thermocouples use two conductors, made up of different metals that are joined at the end to form a junction. When this junction is subjected to heat, a voltage is produced that is directly proportional to the temperature input. They are highly versatile as different metal combinations allow for different measurement ranges; however, they lack the fine accuracy of NTC’s and RTD’s making them the least precise out of the three types

Temperature Probes are a very common and diverse type of temperature sensor. They consist of either a thermistor, a thermocouple or RTD sensing element and can be finished with a terminal head. All three types of sensor can be manufactured into a variety of housing types – stock and bespoke. This allows for enhanced utility, that may span over a multitude of different environments and media that they encounter.

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What is a Temperature Sensor Used for?

Temperature sensors are used to measure temperature in many different applications and industries. They are all around us; present in both everyday life and more industrial settings.

Some application examples are;

Industrial Applications – Monitoring various machinery and environments, power plants, manufacturing.

Scientific and laboratory applications – Science and biotech monitoring.

Medical Applications – Patient monitoring, medical devices, gas analysis, thermodilution cardiac catheters, humidifiers, ventilator flow tubes, dialysis fluid temperature.

Motorsport – Exhaust gas, inlet air temperature, oil temperature and engine temperature measurements.

Domestic appliances – Kitchen appliances (ovens, kettles etc) as well as white goods.

HVAC applications – Heating ventilation and air conditioning devices either commercial or domesticated.

Transit – Refrigerated vans and lorries.

Considerations when Selecting a Temperature Sensor for your Application

When selecting a temperature sensor for use in your application you should take the following into consideration;

Temperature range – Different temperature sensors can measure different ranges and might be more accurate over a certain range. Make sure you check the range of the temperature sensor and the expected range of your application before purchasing. The range of the temperature sensor should be available on the datasheet.

Accuracy and stability – Your application may require a certain degree of accuracy; thermocouples have a higher variance in long term stability compared to thermistors and RTDs, so this is something to be aware of. The temperature sensor with the highest accuracy tends to be the glass coated NTC thermistors.

Size and Package – The space available within the application will have an effect on the type of temperature sensor selected. If space is limited, then a smaller device will be required. Package style is also important as this will determine how the temperature sensor is connected into the application and how the temperature will be measured.