Device for measuring a magnetic field
AssigneeAtware
InventorThierry Augais
Life of this patent
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Abstract
A device for measuring a magnetic material includes four coils having cores made of a superparamagnetic material, and a unit for injecting, into the coils, a direct current and two alternating currents of different frequencies. The value of the magnetic field is derived from the value of the direct current required to cancel an amplitude of a component at a mixing frequency. A structure of the electrical connections to the coils reduces disturbances caused by the alternating currents used with respect to the detection of the component at the mixing frequency. Moreover, specific configurations of the coils reduce the influence of stray electromagnetic radiation on the measurement results. The device can also be used to measure direct currents.
Claims20
Device for measuring a magnetic field, comprising:
- four coils (1-4) of electrical wire with non-linear magnetic cores devoid of hysteresis, called superparamagnetic cores (1N-4N), the four cored coils having identical or substantially identical geometries and electrical and electromagnetic properties, and being electrically connected in series so as to form a chain with two end terminals (A, B) of said chain, a central terminal (C) in said chain, and two secondary terminals (S1, S2) of said chain that are each located between the central terminal and one of the two end terminals;
- means (5) for injecting a direct current (IDC) into the chain of coils, connected to the two end terminals (A, B) of the chain of coils (1-4), and means for adjusting an intensity of the direct current;
- means (6) for injecting a first alternating current (ILF) having a first frequency (LF), connected in order to inject said first alternating current into the chain of coils (1-4) via the central terminal (C), and to recover said first alternating current via the two end terminals (A, B), so that the first alternating current flows with first intensities that are identical or substantially identical via said two end terminals without flowing via the secondary terminals (S1, S2);
- means (7) for injecting a second alternating current (IH) having a second frequency (HF) different from the first frequency (LF), connected in order to inject said second alternating current into the chain of coils (1-4) via the two secondary terminals (S1, S2), and to recover said second alternating current via the central terminal (C) and the two end terminals (A, B) so that the second alternating current flows with second intensities that are identical or substantially identical via the two secondary terminals, and in such a way that said second alternating current flows with third intensities that are identical or substantially identical in all of the coils but in opposite directions between two coils that are successive in the chain;
- and
- means (9) for detecting at least one voltage component that exists between both secondary terminals (S1, S2) of the chain of coils (1-4), a frequency of said voltage component, called mixing frequency, being a linear combination of the first frequency (LF) and the second frequency (HF), with linear combination coefficients that are fixed non-zero integers,
- said device being suitable for simultaneously activating the means (6, 7) for injecting the first (ILF) and second (IHF) alternating currents, and for adjusting the intensity of the direct current (IDC) so as to cancel an amplitude of the voltage component that has the mixing frequency, while said first and second alternating currents are injected,
- so that when the four coils (1-4) are placed in the magnetic field, a value of the intensity of the direct current (IDC) that cancels the amplitude of the voltage component having the mixing frequency is proportional to an intensity of the magnetic field.
Dependencies are inferred from the claim text.