unit 22 provides for that after the disturbance when the power supply is restored the value that has been stored in the intermediate memory 16 before the disturbance is available for a determined period so the output circuit 18 may be able to provide an output signal with a defined value even immediately after the disturbance if the disturbance has a short duration with regard to the variation velocity of the measuring signal then the output signal can append without great error to the signal form before the disturbance thus the output signal experiences only an indispensable error caused by the disturbance in the power supply a longer term deviation in the measuring signal which may be caused by the measuring circuit 12 having a malfunction due to the disturbance of the power supply can thereby be bridged in one embodiment of the invention the integrated circuit 10 is reset after each disturbance during this time the measuring circuit 12 does not provide the desired measuring signal rather the measuring signal takes a defined but undesired value e g the maximum or minimum possible value the measuring circuit is able to provide in this case the above mentioned period of availability of the value which was stored in the intermediate memory 16 before the disturbance is at least so long that it includes the period of reset in this case too the value stored before the disturbance will mostly append better.