Magnetic sensing device and electronic compass using the same
First Claim
1. A magnetic sensing device comprising:
- a magnetic sensor that detects a magnetic field from a change in resistance;
magnetic field generating means for applying an AC magnetic field to the magnetic sensor;
determining means for determining, on the basis of an output voltage corresponding to the applied AC magnetic field, a sensing state of the magnetic sensor;
amplitude controlling means for controlling the amplitude of the AC magnetic field on the basis of a determination result obtained by the determining means;
magnetic field canceling means for supplying a DC current for canceling out an external magnetic field to be sensed, which is superimposed on the magnetic sensor, to the magnetic field generating means; and
output means for obtaining the strength of the external magnetic field from the DC current value and outputting the strength.
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Accused Products
Abstract
[Object] To provide a magnetic sensing device that can obtain the strength of an external magnetic field under circumstances where a relatively strong disturbance takes place, and an electronic compass using the same.
[Solving Means] A current c supplied to a coil 112 and its current deviation x are set. The current c, current c+x, and current c−x are supplied to the coil 112 to generate AC magnetic fields, which are then applied to MR elements 111, and voltages V0 to V2 are detected. Using the voltages V0 to V2 detected by the voltage detector 13, an amplitude determining unit 14 determines whether the magnetic field is outside a sensing range of the MR elements 111. When the magnetic field is outside the sensing range of the MR elements 111, an amplitude controller 17 increases the current deviation x, and the current amplifier 18 supplies current using the current deviation newly set by the amplitude controller 17 to the coil 112. In this manner, the slope of the MR elements 111 is detected.
33 Citations
11 Claims
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1. A magnetic sensing device comprising:
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a magnetic sensor that detects a magnetic field from a change in resistance; magnetic field generating means for applying an AC magnetic field to the magnetic sensor; determining means for determining, on the basis of an output voltage corresponding to the applied AC magnetic field, a sensing state of the magnetic sensor; amplitude controlling means for controlling the amplitude of the AC magnetic field on the basis of a determination result obtained by the determining means; magnetic field canceling means for supplying a DC current for canceling out an external magnetic field to be sensed, which is superimposed on the magnetic sensor, to the magnetic field generating means; and output means for obtaining the strength of the external magnetic field from the DC current value and outputting the strength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification