Abstract: In a signal processor for use in an electronic compass for controlling an offset voltage generated in an analog signal process and automatically controlling an amplification gain, an analog signal processor 52 amplifies signals Sx and Sy, and controls an offset voltage and amplitude A generated during an amplification process. An analog/digital (AD) converter 53 converts analog signals Vadcx and Vadcy from the analog signal processor 52 into a digital signal. A digital signal processor 54 measures a maximum value Vadc—max and a minimum value Vadc—min associated with the digital signal from the AD converter 53, and outputs, to the analog signal processor 52, an offset control signal Soc and a gain control signal Sgc based on the maximum value Vadc—max and minimum value Vadc—min. The signal processor can maintain levels of signals, to be inputted into the AD converter, to be within a reference voltage range.

Abstract: An automatic calibration method for use in an electronic compass. Using the automatic calibration method, the electronic compass automatically calculates and corrects offset and scale values of a geomagnetic signal by detecting one rotation of a geomagnetic axis during a predetermined period of time. The electronic compass calculates an azimuth angle upon receiving geomagnetic data from the geomagnetic sensor, and finds maximum and minimum values of sensor signals of individual axes of the geomagnetic sensor using the received geomagnetic data such that it can correct or calibrate deviation of the azimuth angle. When a time consumed for calibration is the same or shorter than a maximum calibration effective time, the electronic compass determines whether a current state of the detected entry signal indicates a predetermined steady-state flow.

Abstract: A signal processor for use in an electronic compass for controlling an offset voltage generated in an analog signal process and automatically controlling an amplification gain. In the signal processor, an analog signal processor 52 amplifies signals Sx and Sy, and controls an offset voltage and amplitude A generated during an amplification process. An analog/digital (AD) converter 53 converts analog signals Vadcx and Vadcy from the analog signal processor 52 into a digital signal. A digital signal processor 54 measures a maximum value Vadc—max and a minimum value Vadc—min associated with the digital signal from the AD converter 53, and outputs, to the analog signal processor 52, the offset control signal Soc and the gain control signal Sgc based on the maximum value Vad—max and minimum value Vadc—min. The signal processor can maintain levels of signals, to be inputted into the AD converter, to be within a reference voltage range.