.Platinum resistance thermometers (PRT) offer excellent accuracy over a wide temperature range (-200 to +850 ° C). Standard sensors are available from many manufacturers with various precision specifications and numerous packaging options to suit most applications. Unlike thermocouples, it is not necessary to use special cables to connect to the sensor.
The principle of operation is to measure the resistance of a platinum element. The most common type (PT100) has a resistance of 100 ohms at 0 ° C and 138.4 ohms at 100 ° C. There are also PT1000 sensors that have a resistance of 1000 ohms at 0 ° C.
The linearization equation is:
Rt = R0 * (1 + A* t + Bt2 + C(t-100)* t3)
For a PT100 sensor, a 1 °C temperature change will cause a 0.384 ohm change in resistance, so even a small error in measurement of the resistance