Title:
磁気探知装置
Document Type and Number:
Japanese Patent JP4007464
Kind Code:
B2
Abstract:
The present invention relates to a magnetic sensor apparatus which is capable of detecting a very weak magnetic field even when the DC bias magnetic field is at zero and greatly reducing detection output occurring due to factors such as inconsistency of a magnetic body, temperature fluctuations, distortional fluctuations and drift. A magnetic sensor element S generates a pulse-type signal which is in proportion to a rate of change of the magnetic permeability of a magnetic body M and the size of an external magnetic field at a detection winding Wd. A drive circuit 11 cyclically changes the magnetic permeability of the magnetic body by supplying a pulse-type drive current for sampling to the magnetic body. A peak value detection unit 12 detects a positive peak value and a negative peak value of the pulse-type signal. A feedback circuit supplies an AC current which is in synchronization with the pulse-type drive current to the detection winding and also superimposes a DC current component on the AC current to set the absolute values of the positive peak value and the negative peak value equal to each other. The size of a magnetic field to be detected is detected based upon a DC current component at the detection winding.
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Inventors:
Kazuo Fukunaga
Application Number:
JP28756797A
Publication Date:
November 14, 2007
Filing Date:
October 06, 1997
Export Citation:
Assignee:
tdk Corporation
International Classes:
G01C17/32; G01R33/04
Domestic Patent References:
| JP3092782A | ||||
| JP9005084A | ||||
| JP62105069A |
Attorney, Agent or Firm:
Takashi Murai