Resistance thermometers are based on the physical effect that metals also change their electrical resistance when their temperature changes. These changes are particularly strong in pure metals. Temperature sensors, so-called measuring resistors, are therefore often made from platinum (Pt 100), which has the additional benefit of being resistant to corrosion and ageing. The classic method of temperature measurement with resistance thermometers is invasive, i.e. the Pt 100 probe is inserted directly into the medium through a hole in the container or tube. A non-invasive alternative for hygienic measurement on tubes is provided by the clamp-on solution. In this case, the thermometer is clamped onto the outside of the tube and measures the temperature of the outer tube surface.