Electricity: measuring and testing – Magnetic – Displacement
Patent
1998-08-17
2000-11-28
Strecker, Gerard
Electricity: measuring and testing
Magnetic
Displacement
324174, 324252, 338 32R, G01B 730, G01R 3309, G01D 516
Patent
active
061540250
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for determining the position of an object with respect to a predetermined initial position without contact, as well as to a use of the device as a contactless potentiometer.
RELATED TECHNOLOGY
In layers of ferromagnetic transition metals such as Ni, Fe or Co or alloys thereof, the electric resistance may depend on the size and direction of a magnetic field permeating the material. The effect occurring with such layers is called "anisotropic magnetoresistance (AMR)" or "anisotropic magnetoresistive effect." It is based physically on the different scattering cross sections of electrons with a different spin and spin polarity of the D band. The electrons are referred to as majority and minority electrons. For the corresponding magnetoresistive sensors, a thin layer of such a magnetoresistive material, with magnetization in the plane of the layer, is generally provided. The change in resistance when the magnetization is rotated with respect to the direction of a current passed through the sensor may then amount to a few percent of the normal isotropic (=ohmic) resistance. Furthermore, it has long been known that magnetoresistive multilayer systems may be designed containing ferromagnetic layers arranged in a stack, with the layers separated by intermediate metallic layers and with the magnetization always lying in the plane of the layer. The thickness of the individual layers is selected so it is much smaller than the mean free path length of the conduction electrons. In such multilayer systems, a "giant magnetoresistive effect" or "giant magnetoresistance (GMR)" may also occur in addition to the above-mentioned anisotropic magnetoresistive effect AMR (see, for example, European Patent EP-A 483,373). Such a GMR effect is based on the difference in scattering of majority and minority conduction electrons at the interfaces between the ferromagnetic layers and the adjacent layers as well as scattering effects within these layers, in particular when using alloys. The GMR effect is an isotropic effect, which can be much greater than the anisotropic effect AMR. In such multilayer systems having a GMR effect, adjacent metallic layers are at first oppositely magnetized, with a bias layer or a bias layer part being magnetically harder than a measurement layer. Under the influence of an external magnetic field, i.e., a component of this field which is manifested in the plane of the layer, the initial antiparallel orientation of the magnetizations may then be converted to a parallel orientation. This fact is utilized in corresponding magnetic field sensors.
Such a sensor is derived from International Patent Application WO94/17426. It is part of a device for contactless determination of an angular position of an object. For this purpose, the object is rigidly connected to a permanent magnet which is rotatably arranged in a plane parallel to a measurement layer plane. This magnet generates in the measurement layer a magnetic field component which is thus rotatable with respect to a preferential magnetic axis of a bias part of the sensor and therefore causes the magnetization in the magnetically softer measurement layer to rotate in a similar manner. The electric resistance of the sensor thus depends on the angle between the magnetization of the measurement layer and the preferential direction of magnetization of the bias part. This dependence is generally anisotropic owing to the predetermined shape (geometry) of the layer structure of the sensor. Such a device for detecting an angular position, which may form a contactless potentiometer in particular, is restricted, however, to a common axis of symmetry of the magnet and the sensor about which either the magnet or the sensor itself is rotatably arranged.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a device in which the above-described restriction is at least substantially eliminated.
This object is achieved according to the present invention by the fact that the magnetic
REFERENCES:
patent: 4754221 (1988-06-01), Ao et al.
patent: 5574364 (1996-11-01), Kajimoto et al.
patent: 5650721 (1997-07-01), van den Berg et al.
patent: 5744950 (1998-04-01), Seefeldt
patent: 5841275 (1998-11-01), Spies
Siemens Magnetic Sensors Data Book, "Hall-effect Generators", 1989, pp. 56-59.
Clemens Wolfgang
Schelter Wolfgang
Schmidt Ludwig
Vieth Michael
Siemens AG
Strecker Gerard
LandOfFree
Contactless potentiometer and device for contactlessly sensing a does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Contactless potentiometer and device for contactlessly sensing a, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Contactless potentiometer and device for contactlessly sensing a will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1729250