To measure the thermal displacements under service conditions, the device should perform continuous movements, in wich the grab breaks forth after a certain time to a defined measuring point at which the repeatability of the three main axis directions of three precision measurement feeler or inductive is measured. The thermal displacements to wear as a function of time in a diagram. Parallel to the shift measurements, the temperatures are at prominent places of the unit detects a resistance thermometer to obtain detailed conclusions about the causes of the thermal displacements.