Technical Blog

Selecting Temperature Sensor; Things to Consider

Temperature Range 

Temperature range should be the first consideration when selecting a temperature sensor for an application. Different temperature sensors will be more suited to different ranges.

NTC thermistors are well suited to applications from -50° up to +250°C and so are well suited to a range of applications.

Thermocouples are less accurate at lower temperatures but are able to measure temperatures up to 2000°C.

Accuracy 

The required accuracy is another important consideration. Thermocouples, although they are low cost, are often less accurate over time than a thermistor temperature probe.  

NTC thermistors and thermistor probes are the most accurate between -50C and +150°C and if they are glass encapsulated can also be extremely accurate at 250°C.

Stability 

Is the operation long term? This will affect the type of temperature sensor which is used. Temperature sensors can become less effective over time depending on their construction, materials they are constructed from and the packaging.

Over the course of a year, a thermistor can change by 0.02°C to 0.2°C depending on whether or not it is hermetically sealed. A Thermocouple can change by 1°C - 2°C over the course of a year.

Size or Packaging Style 

The packaging style will differ depending on the application in hand. A threaded stud may be used for some general purpose applications. Closed tubes are well suited to applications involving liquid measurement. For surface sensing, ring terminals and other thin round metal stampings can be used.

Noise Immunity 

NTC thermistors possess high resistance during the initial switch on making them immune to electrical noise and lead resistance. Thermocouples are also immune to lead resistance although can be affected by electrical noise because of the small output signal.

For more information on the temperature sensors we can offer take a look at our Temperature section on our website. You may also find our NTC thermistor page useful. Many of our temperature sensors are bespoke so please contact us if you have a requirement: +44(0)1327 351004 or sales@variohm.com