Detector for magnetism using a resistance element

• US 5,182,515 A
• Filed: 07/25/1990
• Issued: 01/26/1993
• Est. Priority Date: 04/24/1987
• Status: Expired due to Fees

• Current Assignee: Wacoh Company
• Original Assignee: Wacoh Company
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Razavi, Michael
• Assistant Examiner(s): DOUGHERTY, ELIZABETH L
• Application Number:
  US07/559,381
• Time in Patent Office: 916 Days
• Field of Search: 73/862.04, 73/862.67, 73/862.68, 73/777, 73/517 R, 73/DIG. 10, 324/259, 324/260
• US Class Current: 324/259
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 5/162 of piezoresistors
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: G01R 33/038 using permanent magnets, e.g. balances, torsion devices
• CPC Class Codes: Y10S 73/10 instrument mechanisms with acceleration compensation

Abstract

A force detector is comprised of resistance elements having a piezo resistance effect such that electric resistance varies due to mechanical deformation, and formed on a single crystal substrate (10), and a strain generative body (20) having a supporting portion (21) and a working portion (23), thus allowing the resistance elements to produce a mechanical deformation on the basis of a displacement with respect to the supporting portion of the working portion. This force detector can detect a force applied to the working portion as changes in resistance values of the resistance elements. The plane on which resistance elements are to be formed on the single crystal substrate is selected so that piezo resistance coefficients in two directions perpendicular to each other exhibit peak. When a weight body (30) is connected to the working portion, it is possible to detect an acceleration acting on the weight body. Moreover, when a magnetic body (330) is connected to the working portion, it is possible to detect a nagnetic force acting on the magnetic body. By using the detector system for acceleration in common to the detector system for magnetic force to perform a compensation computation, detection of a magnetic force which is not influences by acceleration can be made. By devising an arerangement of resistance elements in either detector, it is possible to independently determine magnitudes of objects to be measured with respect to directions of the three-dimensional coordinate system, respectively.

Claims

1. A magnetism detector for detecting magnetism in at least two axial directions in a three-dimensional coordinate system expressed by three axes of X, Y and Z, the detector comprising:

a single crystal substrate having a surface extending along an XY-plane, at least four resistance elements which have a piezo resistance effect such that electric resistance varies due to mechanical deformation of said surface,

a strain generative body having a supporting portion and a working portion, said working portion being displaceable with respect to said supporting portion so as to produce a mechanical deformation of said supporting portion, and

a magnetic body connected to said working portion so as to allow said working portion to undergo a displacement in response to a magnetic force to which said magnetic body is exposed for mechanically deforming said supporting portion,

said substrate being mechanically connected to said supporting portion so that a mechanical deformation of said supporting portion is transmitted to said substrate, and

a bridge circuit being formed by said four resistance elements for detecting said magnetic force in each of two of said axial directions, respectively.

2. A magnetism detector comprising:

(1) first detector means comprising;

a single crystal substrate having a resistance element which has a piezo resistance effect such that electric resistance varies due to mechanical deformation,

a strain generative body having a supporting portion and a working portion, said working portion being displaceable with respect to said supporting portion so as to produce a mechanical deformation of said strain supporting portion, and

a magnetic body connected to said working portion so as to allow said working portion to undergo a displacement in response to a magnetic force to which said magnetic body is exposed,

said substrate being mechanically connected to said supporting portion so that a mechanical deformation of said supporting portion is transmitted to said substrate,

(2) second detector means comprising;

a single crystal substrate having a resistance element which has a piezo resistance effect such that electric resistance varies due to mechanical deformation,

a strain generative body having a supporting portion and a working portion, said working portion being displaceable with respect to said supporting portion so as to produce a mechanical deformation of said supporting portion, and

a weight body connected to said working portion so as to allow said working portion to undergo a displacement corresponding to an applied acceleration, and being made of a material of different magnetic properties from that of said magnetic body,

said substrate being mechanically connected to said supporting portion so that a mechanical deformation of said supporting portion is transmitted to said substrate, and

(3) compensation computation means for inputting a change in a resistance value of said resistance element of said first detector means and a change in a resistance value of said resistance element of said second detector means as first and second data, respectively, to cancel influence of an acceleration of said magnetic body on the basis of said both data, thus to calculate only a magnetic force acting on said magnetic body.

3. A magnetism detector as set forth in claim 2, wherein said first detector means includes at least four resistance elements for detecting a force responsive to the magnetism in at least two axial directions in a three-dimensional coordinate system, and

said second detector means includes at least four resistance elements for detecting a force resulting from an acceleration in said axial directions.

4. A magnetism detector for detecting magnetism in at least two axial directions in a three-dimensional coordinate system expressed by three axes of X, Y and Z, the detector comprising:

a single crystal substrate having a surface extending along an XY-plane, at least four resistance elements which have a piezo resistance effect such that electric resistance varies due to a mechanical deformation of said surface, said substrate having a supporting portion and a working portion, said working portion being displaceable with respect to said supporting portion so as to produce a mechanical deformation of said substrate, and

a magnetic body connected to said working portion so as to allow said working portion to undergo a displacement in response to a magnetic force to which said magnetic body is exposed, and

a bridge circuit being formed by said four resistance elements for detecting said magnetic force in each of two of said axial directions, respectively.

5. A magnetism detector comprising:

(1) first detector means comprising;

a single crystal substrate having a resistance element which has a piezo resistance effect such that electric resistance varies due to mechanical deformation, said substrate having a supporting portion and a working portion, said working portion being displaceable with respect to said supporting portion so as to produce a mechanical deformation of said substrate, and

a magnetic body connected to said working portion so as to allow said working portion to undergo a displacement in response to a magnetic force to which said magnetic body is exposed,

(2) second detector means comprising;

a single crystal substrate having a resistance element which has a piezo resistance effect such that electric resistance varies due to mechanical deformation, said substrate having a supporting portion and a working portion, said working portion being displaceable with respect to said supporting portion so as to produce a mechanical deformation of said substrate, and

a weight body connected to said working portion so as to allow said working portion to undergo a displacement corresponding to an applied acceleration, and being made of a material of different magnetic properties from that of said magnetic body, and

(3) compensation computation means for inputting a change in a resistance value of said resistance element of said first detector means and a change in a resistance value of said resistance element of said second detector means as first and second data, respectively, to cancel influence of an acceleration of said magnetic body on the basis of said both data, thus to calculate only a magnetic force acting on said magnetic body.

6. A magnetism detector as set forth in claim 5, wherein said first detector means includes at least four resistance elements for detecting a force responsive to the magnetism in at least two axial directions in a three-dimensional coordinate system, and

said second detector means includes at least four resistance elements for detecting a force resulting from an acceleration in said axial directions.