Temperature Dependent Changes in Electrical Resistance

Platinum sensors exploit the fact the electrical resistance of platimum metal is temperature dependent. This behaviour can be described by a polynomial of the form 

Here R0 is the resistance at 0°C, and a and b are coefficients whose values are specified in internationally agreed standards covering platinum temperature sensors, for example DIN EN 60751. The coefficient b is so small that for most applications one can assume a linear relation between Rt and the temperature t. 

For each type of sensor, a classification framework sets precision tolerance ratings. Platinum temperature sensors have a positive temperature coefficient which is defined as  

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