Electrical resistors – Resistance value responsive to a condition – Magnetic field or compass
Patent
1996-08-23
1998-01-13
Hecker, Stuart N.
Electrical resistors
Resistance value responsive to a condition
Magnetic field or compass
324252, H01L 4300, G01R 3302
Patent
active
057084076
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a current sensor comprising a magnetoresistive tape and to its production process. This sensor or transducer is to be used for measuring currents carried by electrical conductors. It can be used for the manufacture of ammeters, for the detection of threshold currents (maxima or minima) and for the detection of current losses by differential measurement between two sensors constructed in accordance with the invention.
Among current sensors, some make it possible to measure the current flowing in a circuit without having to insert a device in the actual circuit. They have the advantage of not modifying existing electrical arrangements. Their operating principle is based on the detection of the magnetic fields created by the passage of currents in the conductors.
Current sensors of this type are known, which use the magnetoresistive effect of certain materials for evaluating the value of the current flowing in a conductor by means of the magnetic field flowing round said conductor and generated by said current.
A material has a magnetoresistive effect as soon as its resistivity varies in the presence of a magnetic field. This variation is generally in the form of a reduction of the resistivity from a maximum value corresponding to an absence of magnetic field applied to a minimum value corresponding to a saturation magnetic field for said material. There is no further reduction to the resistivity of the material beyond the saturation magnetic field. Thus, the resistivity decrease zone offers the possibility of measuring electric currents.
U.S. Pat. No. 4,937,521 and DE-A-3 929 452 disclose current sensors using the magnetoresistive effect. The magnetoresistive component used is constituted by a single layer or film and is of the ferromagnetic type. It is generally formed from transition metal alloys (iron, nickel, cobalt). This component has an anisotropic magnetoresistive effect dependent on the angle existing between the magnetization direction of the material and the direction of the current made to flow in the magnetoresistive component. A bar-shaped magnetoresistive component has its magnetization generally aligned in parallel with the length of said bar. The resistivity of these components is then insensitive to magnetic fields applied in the same direction. Thus, these components have an anisotropic magnetoresistive effect. The magnetoresistive components of current sensors according to the prior art must be designed as a function thereof.
Thus, the magnetoresistive component of U.S. Pat. No. 4,937,521 has a winding shape, as shown in the attached FIG. 1. The magnetoresistive component 1 is deposited on a rigid, insulating substrate 2 perforated by a central hole 3, the component 1 being located around said hole. Its ends are connected to two contacts 4 and 5 permitting its linking with an external circuit having a magnetization and a measuring device detecting the resistivity variations of the component 1. The central hole 3 is used for the passage of the conductor, whereof the current flowing therethrough is to be measured. A current I.sub.1 induces a magnetic field H.sub.1. Only those parts of the component 1 transverse to the field H.sub.1 will have their resistivity modified by the presence of the field H.sub.1. The parts of component 1 parallel to the field H.sub.1 will not undergo a resistivity modification.
The magnetoresistive component of DE-A-3 929 452 is based on a geometry comparable to that of the preceding document. The electrical parts parallel to the magnetic field are made from a non-magnetic, good conducting material. The parts transverse to the magnetic field are made from a magnetoresistive material and are partly covered with a system of conductive microtongues oriented at 45.degree. from the axis of the magnetoresistive component.
Therefore the prior art magnetoresistive components suffer from the disadvantage that only one part of their structure implements the magnetoresistive effect. They are also produced on rigid supports limiting a collectiv
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Boileau Franck
Fedeli Jean-Marc
Mas Patrick
Mouchot Jean
Commissariat a l''Energie Atomique
Hecker Stuart N.
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