Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
1999-05-10
2001-02-06
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S11700H
Reexamination Certificate
active
06184679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a magnetic field sensor of the kind having two flux concentrators and a sensor for measuring a magnetic field, wherein the flux concentrators are separated by an air gap.
2. Description of the Prior Art
U.S. Pat. No. 4,749,939 discloses a magnetic field sensor for measuring the energy transported through an electric conductor. The magnetic field sensor has a vertical Hall element and two magnetic flux concentrators. The flux concentrators and an external yoke form a magnetic circuit of ferromagnetic material, in the air gap of which the Hall element is disposed.
The flux concentrators are of a configuration such as to reduce in width towards the Hall element in order to produce a magnetic field which is as high as possible in the air gap in relation to the current flowing in the conductor, and thus to achieve a high level of sensitivity. The geometry of the flux concentrators is optimised in such a way that the magnetic flux outside the air gap, that is to say the leakage field component, is as small as possible so that the linearity of the magnetic field sensor is not adversely affected by saturation effects of the flux concentrators. The minimum possible width of the air gap is limited in a downward direction by the dimensions of the Hall element disposed in the air gap.
Although it is possible with horizontal Hall elements further to reduce the dimensions of the air gap, as however the flux concentrators in principle must be of a different configuration in order to pass the magnetic field through the Hall element, such an arrangement is sensitive to interference fields which act on the Hall element in a perpendicular direction.
SUMMARY OF THE INVENTION
The object of the present invention is to propose a magnetic field sensor for measuring weak magnetic fields, which has a high level of accuracy and which is less sensitive to interference fields.
According to a first aspect, the present invention provides a magnetic field sensor having two flux concentrators and a sensor for measuring a magnetic field, wherein the flux concentrators are separated by an air gap, and wherein two Hall elements serve as the sensor, the Hall elements being arranged outside the air gap and at least a part of the field lines of the magnetic field, which lead from the first flux concentrator to the second flux concentrator, passes through the two Hall elements in approximately opposite directions.
According to a second aspect, the present invention provides a magnetic field sensor having two flux concentrators and a Hall element for measuring a magnetic field, wherein the flux concentrators are separated by an air gap, and wherein the Hall element is arranged outside the air gap and at least a part of the field lines of the magnetic field, which lead from the first flux concentrator to the second flux concentrator, passes through the Hall element in approximately opposite directions.
Advantageous configurations are set forth in the appendant claims.
REFERENCES:
patent: 3736441 (1973-05-01), Masuda et al.
patent: 4692703 (1987-09-01), Extance et al.
patent: 4765345 (1988-08-01), Adib
patent: 5041780 (1991-08-01), Ripple
patent: 5247202 (1993-09-01), Popovic et al.
patent: 5483161 (1996-01-01), Deeter et al.
patent: 5719496 (1998-02-01), Wolf
patent: 5793200 (1998-08-01), Berrill
patent: 5874848 (1999-02-01), Drafts et al.
Blanchard Hubert
Hrejsa Jan
Popovic Radivoje
Racz Robert
Patidar Jay
Proskauer Rose LLP
Sentron AG
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