To easily adjust detection voltage by calculating a correction value at the time of applying reference voltage and adding the correction value to measurement voltage.
CPU 6 starts a battery voltage correction program stored in F-ROM 7. A battery pack 1 is taken out and external reference voltage V is connected instead. External reference voltage V is divided into 1/2 by division resistances 2 and 3 and they become internal reference voltage. It is inputted to an A/D converter 5. A difference between external reference voltage V and measurement voltage is set to be the correction value and is stored in F-ROM 7. At a battery voltage detection mode, the battery voltage of the battery pack 1 is inputted and the correction value is added to measurement voltage at that time so as to make it to be detection voltage. The correction value is calculated and the correction value is added to measurement voltage. Thus, detection voltage can precisely be adjusted by absorbing the fluctuation of the respective parts of a device. Thus, detection voltage can highly precisely be adjusted by detecting a peripheral temperature and correcting fluctuation owing to the temperature.
TSUKUDA MASATO
NISHIMURA TADAO
NAKAMURA MASAHIRO
FUJITANI KEIJI
