Those are iron and nickel based alloys which are characterised by their high temperature coefficient which confers them a very important variation of resistance .
They are also characterized by their dilatation at some temperatures.
Their resistivity is relatively high (from 0,20 up to 0,83 ohm mm² / m).
They often intervene in the applications where is necessary an autoregulation of the power (thermostats), but also in the manufacture of leading-in for lamps (capping with the glass).
The alloy is used for its property to have a linear expansion coefficient null..
