A temperature coefficient
describes the relative change of a physical property that is associated
with a given change in temperature.
For a property R that changes by dR when the temperature changes by dT, the temperature coefficient α is defined by
If the temperature coefficient itself does not vary too much with temperature, a linear approximation can be used to determine the value R of a property at a temperature T, given its value R0 at a reference temperature T0:
Using a material that has low room temperature resistance is also important. Lower resistance across the detecting material mean less power will need to be used. Also, there is a relationship between resistance and noise, the higher the resistance the higher the noise. Thus, for easier detection and to satisfy the low noise requirement, resistance should be low.