Types of RTD’s
Platinum RTDs typically are provided in two classes; Class A and Class B.
Class A is considered high accuracy and has an ice point tolerance of 0.06 ohms.
Class B is standard accuracy and has an ice point tolerance of 0.12 ohms. Class B is widely used by most industries.
The accuracy will decrease with temperature. Class A will have an accuracy of 0.43 ohms ( 1.45ºC) at 600ºC and class B will be 1.06 ohms ( 3.3ºC) at 600ºC. The chart below shows the tolerance versus temperature (IEC 751).
Other accuracy classes like 1/3, 1/5, 1/10 of class B are available.
Platinum resistance temperature sensors (PRT) They offer excellent accuracy over a wide temperature range(from -200 to +850ºC).
Other resistance value options
RTD elements are also available with resistances of 200, 500, and 1000 O at 0ºC. Such type of
RTDs is normally known as PT200, PT 500, and PT 1000 respectively. These RTDs have the same temperature coefficients as previously described, but because of their higher resistances at 0ºC, they provide more resistance change per degree, allowing for greater resolution.
Standard Platinum RTDs (SPRTs)