The temperature shift is measured with the help of thermistors. These are resistors made of semiconducting ceramics on the basis of Mn, Ni, Co, Cu, Fe and U oxidases with a high negative temperature coefficient of the electric impedance. The linear size of the modern thermistors does not exceed several millimeters. The temperature dependence of the thermistor resistance R is expressed by the empirical Steinhart–Hart Eq. (3.94 ).