|Carl Wilhelm Siemens thermometry|
In 1821, Humphry Davy had observed that conductance of metals varied according to temperature but Davy hadn’t shown that this property could be used to make a thermometer. In 1871, Carl Wilhelm Siemens claimed that platinum would be the best metal for a resistance thermometer, having the most stable relation between resistance and temperature over the greatest range.
How to calibrate
Adjust the sensor to give an accurate reading for a known state of a pure substance, such as the triple point of water. Adjust the sensor to replicate the readings of another sensor that is known to be accurate. Be sure to calibrate the sensor over the range of temperatures in which the sensor is intended to be used.
When a delicate wire gets really hot, it melts, making its resistance a moot question. When it gets incredibly cold, its resistance becomes independent of temperature. Ideally, behavior depends on principles, but in practice can randomly misbehave.