| 摘要 |
To reduce a dispersion in a sensitivity of a magnetism detecting circuit driving, by current, a magnetism sensor comprising magnetism resistance elements in a bridge constitution to a dispersion in a sensitivity of a magnetism sensor. An electronic azimuth meter is provided with EEPROM and drive current set values are previously stored to EEPROM. The drive current set values are calculated by a predetermined calculation by measuring bridge resistance of a magnetism sensor of the electronic azimuth meter. In detecting magnetism by the magnetism sensor, CPU controls a sensor drive circuit based on the drive current set values stored to EEPROM. Thereby, the sensor drive circuit supplies a magnetism sensor with optimum drive current in accordance with a bridge resistance value thereof.
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