A Pt100 sensor changes its electrical resistance with every change in temperature in its environment. Its resistance value is 100 Ohms at 0°C. This characteristic is used in a bridge circuit to generate a signal suitable for further processing.
There are five quality classes with the following tolerances at 0°C defined by the IEC 60751:2008.
Class B: ±0,3 K
Class A: ±0,15 K
Class B 1/3: ±0,1 K
Class B 1/5: ±0,06 K
Class B 1/10: ±0,03 K
The table below illustrates the tolerances for each Pt100 sensor class at different temperatures.
Class AA: tg = 0,1 K + 0,0017 · t
Class A: tg = 0,15 K + 0,002 · t
Class B: tg = 0,30 K + 0,005 · t
Class C: tg = 0,6 K + 0,01 · t
Example for Class B: At 200°C deviations in the measured value of up to ± 1.3 K are allowed.