a power of the shaft 13 the power of the shaft 13 is determined from a product of the torque 23 of the shaft 13 and the present angular speed of the shaft in particular if the load bearing force determination step 21 is performed by monitoring of the deformation of the carrier elements 7 it is possible according to the invention before the load bearing force determination step 21 to determine a relationship between the deformation of the carrier elements 7 and an additionally applied force in order to perform a calibration 19 of the sensors 9 for this purpose it is the case in particular that a negative pressure is applied in the turbine housing 3 owing to the decrease of the pressure in the turbine housing 3 the turbine housing 3 is acted on by the ambient pressure 14 as positive pressure in this case the ambient pressure acts on the surface area of the cross section of the inflow compensator 11 since the effected pressure difference between turbine housing pressure and ambient pressure 14 and the cross sectional area of the inflow compensator 11 are known the force additionally acting on the turbine housing is also known the additional force and the elastic deformation of the carrier elements 7 vary linearly with respect to one another this possibility for calibration 19 exists in particular for reasons relating to type of construction in the case of steam turbines 2 which are already assigned evacuation.