| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a magnetic sensor which uses a magnetism detection (MI) element, which is hardly influenced by a change in a power-supply voltage and by the temperature characteristic or the like of an electric element and in which it is not required to fine adjust an oscillation circuit. SOLUTION: An AC bias current is made to flow to a coil 22 which is wound on an MI element 1 built in a Colpitts oscillation circuit, and an AC bias magnetic field is applied to the MI element 1. Due to a change in the impedance of the MI element 1 according to an external magnetic field and to a bias magnetic field, an amplitude- modulated waveform whose peaks have a height difference alternately is obtained as the output of the oscillation circuit. Then, the height difference corresponds to the intensity of the external magnetic field. The output of the oscillation circuit is detected by a detection circuit, its DC portion is removed so as to be input to a comparator, and an output signal in a pulse-width-modulated digital waveform is obtained according to the height difference. The intensity of the external magnetic field is found not by the absolute value of the output of the oscillation circuit but by a change portion.</p> |
