An ADC code given in response to input of an analog input value to an A/D converter circuit is measured at a site where an A/D converter unit is used to measure a user-measured value. A user-set value calculating part calculates a user offset value and a user gain value on the basis of one user-measured value, a factory offset value, and a factory gain value, and stores the calculated user offset value and the user gain value in a nonvolatile memory.