Abstract: A measure obtained by a counting circuit (2) is converted by a processing circuit (3) to an indication angle signal at a predetermined conversion cycle. A smoothing circuit (4) comprises a division circuit (11) for calculating the difference between the previous indication angle data .theta..sub.0 and the present indication angle data .theta..sub.1 which is outputted after the conversion cycle T and has changed, and sequentially accumulating the angle data corresponding to T/n (where n is an integer of 2 or more) shorter than the conversion cycle T at a division cycle T/n and a voltage memory (12) for converting and outputting a two-phase driving signal for driving a stepper motor type measuring instrument (6) on the basis of the indication angle data .theta..sub.i outputted from the division circuit (11) every division cycle T/n. A voltage signal is generated through an output circuit (5) for converting the signal to a voltage signal to be applied to a two-phase excitation coil of a stepper motor.