It defines the relationship between Temperature and resistance thus,

For the range -200°C to 0°C

R_t=R₀ [ 1 + At + Bt² + C(t-100°C)t³]

For the range °C to 850°C

R_t=R₀( 1 + At + Bt²)

For the quality of platinum commonly used in industrial platinum resistance thermometers, the values of the constants are:

A = 3.9083 x 10 ^-3°C^-1
B = -5.775 x 10 ^-7°C^-2
C = -4.183 x 10 ^-12°C^-4


Technical Data Construction
Detectors can be of two basic constructions, wire wound and flat film. Film thermometers can be of thin film or thick film type.
For superior performance TDI detectors are all of the partially supported wire wound type. In this construction the wire is wound into a very small coil and inserted into axial holes in a high purity alumina rod. A small quantity of glass adhesive is introduced into these holes which, after firing, firmly secures part of each turn onto the alumina. This results in a detector in which the majority of the platinum wire is free to move, giving excellent long term stability, and which will withstand levels of vibration up to 30G without damage. The operating temperature range covered is from -200°C to +800°C, and the units will continue to operate up to, and be undamaged by, temperatures as high as 1100°C