Working With PT100 Temperature Sensors

Highly accurate and stable temperature measurement is possible with a PT100 temperature sensor between -200 and +850°C, which makes it a popular choice in many industrial applications. In particular, the high degree of accuracy across the -50 to 150ºC range means that it is the preferred choice for temperature measurement in Pharmaceutical applications, such as in sterilisation processes.

The following guidelines will help users to specify the correct configuration.

They are written with Pharmaceutical and Healthcare applications in mind although the concepts apply across all industry sectors.

What is a PT100 Temperature Sensor?

The PT100 sensor is a popular example of a resistance temperature detector (RTD). It is based on the principle observed in metals whereby a change in temperature will cause a change in the resistance of the material. Platinum exibits a positive temperature coefficient I.e it shows an increasing resistance with increasing temperature, and so is the most common material used to construct RTD’s.

The PT100 sensor is designed to have a resistance of exactly 100Ω at 0.0°C, and a resistance increase of 0.385Ω per 1°C increase between 0 and 100°C according to ISO 60751: 2008 pyrometer

PT100 sensors are commonly constructed using two methods:

Wire wound sensors

Platinum wire wound sensors consist of a thin platinum wire loosely wrapped around, or threaded within, a ceramic core.

Wire wound sensors can be used over a wide range of temperatures, however they can be susceptible to mechanical shock, which induces measurement drift.

Thin Film Sensors

Thin film sensors are based upon a ceramic substrate with a deposition of high purity platinum, laser etched to give 100Ω at 0.0°C. This is then sealed within a glass adhesive.

These sensors are cheaper than wire wound detectors, and are less sensitive to impact damage. However they operate within a smaller temperature range than wire wound sensors.

PT100 sensors are commercially available to several different tolerance levels, according to BS EN 60751:2008, as class B, A and AA in order of increasing precision. In addition 1/10 DIN sensors are available which are picked to ensure a tolerance band 1/10th that of a Class B detector.

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