PURPOSE: To improve easily the accuracy of the lineality by correcting an output of a current integration circuit with range switching.

CONSTITUTION: An integrating capacity in correspondence to a relay which is turned on is measured beforehand, and a ratio from the prescribed capacity is obtained and stored as a correction coefficient of integrating capacity at a correction coefficient storing circuit part 18 of integrating capacity. Then an output signal of an A/D converter 16 and a correction coefficient read out of the circuit part 18 are calculated at an arithmetic control circuit part 17. Thus the calculated result is outputted as a digital output having corrected errors of the integrating capacity to an external signal terminal.