A memory stores correction coefficients for correcting variations of resistance values of coils L.sub.s and L.sub.c depending upon a temperature. A temperature or a resistance value of a cross coil meter is detected, and an output of a microcomputer is corrected using a correction coefficient stored in the memory. In accordance with the corrected output, a current amount to be supplied to the cross coil meter is controlled. Therefore, the cross coil meter can receive a predetermined amount of current regardless of a temperature variation.