There are two ways of measuring temperature in solid, liquid or gaseous media in measurement and control technology. One is the use of the thermoelectric Seebeck effect from physics, where, to put it simply, two differently alloyed wires generate a thermoelectric voltage. The other possibility is to use the temperature behaviour of a metallic resistor e.g. PT100 / Ni100. The linear temperature behaviour of the platinum resistance is used here. The IEC / EN 60751 standard describes and defines the temperature/resistance relationship for industrial PT100 temperature sensors. The international standard applies to PT100 sensors whose temperature coefficient α=3.851x10-3°C-1 has been designated. The PT100 sensors are installed in resistance thermometer measuring inserts according to DIN 43735 in a protective fitting according to DIN 43722.