DEVICE AND METHOD FOR MEASURING MAGNETIC FIELD(S) WITH CALIBRATION SUPERIMPOSED ON THE MEASUREMENT AND CORRESPONDING USES

• US 20030151404A1
• Filed: 10/15/2002
• Published: 08/14/2003
• Est. Priority Date: 04/14/2000
• Status: Active Grant

• Current Assignee: Thales Avionics SA (Thales SA)
• Original Assignee: Thales Avionics SA (Thales SA)
• Inventors: Lescourret, Jean-Louis
• Granted Patent: US 6,894,490 B2
• Time in Patent Office: Days
• US Class Current: 324/228
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G01V 13/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00

Abstract

The invention relates to a device for measuring magnetic field(s). This device comprises at least one measurement acquisition pathway (22₁, 22₂, 22₃; 23₁, 23₂, 23₃) comprising a measurement current generator (24), a coil (25), a measurement resistor (26), at least one amplifier (27) and at least one antialiasing filter, delivering a measurement voltage.

According to the invention, the device for measuring magnetic field(s) comprises means for determination of at least one electrical quantity representative of said acquisition pathway. These means of determination comprise means of injection (21) of a predetermined calibration current, comprising at least two frequency terms at at least two frequencies distinct from that (those) of said measurement current, said calibration current being superimposed on said measurement current. The device for measuring magnetic field(s) also comprises calculation means delivering an estimate of said at least one electrical quantity at the frequency or frequencies of said measurement current.

Claims

1. A device for measuring magnetic field(s), comprising at least one measurement acquisition pathway (22₁, 22₂, 22₃;

23₁, 23₂, 23₃) comprising a measurement current generator (24;

442), a coil (13;

25;

443, 461, 462), a measurement resistor (26;

463), at least one amplifier (27) and at least one antialiasing filter (43), delivering a measurement voltage,

characterized in that it comprises means for determination of at least one electrical quantity representative of said acquisition pathway, said means of determination comprising means of injection (21) of a predetermined calibration current, comprising at least two frequency terms at at least two frequencies distinct from that (those) of said measurement current, said calibration current being superimposed on said measurement current, and calculation means delivering an estimate of said at least one electrical quantity at the frequency or frequencies of said measurement current.

2. The device as claimed in claim 1, characterized in that said at least one electrical quantity representative of said acquisition pathway belongs to the group comprising:

the transfer function of said acquisition pathway;

a calibration output voltage of said acquisition pathway.

3. The device as claimed in either of claims 1 and 2, characterized in that said means of injection of said calibration current are implemented in the course of a calibration cycle, in at least two distinct measurement acquisition pathways.

4. The device as claimed in any one of claims 1 to 3, characterized in that said means of injection of said calibration current are implemented in the course of a calibration cycle, on the one hand in an emitter of magnetic field(s) (1;

44), and on the other hand in a sensor of magnetic field(s) (11;

46).

5. The device as claimed in claim 4, characterized in that said emitter and said sensor defining a reference frame in space each comprise three acquisition pathways,

processing means making it possible to determine the position and the orientation of said sensor with respect to said emitter.

6. The device as claimed in any one of claims 3 to 5, characterized in that said means of injection of said calibration current are implemented successively in each of said acquisition pathways in the course of said calibration cycle.

7. The device as claimed in any one of claims 3 to 6, characterized in that said means of injection of said calibration current implement a current generator (451) of very large internal impedance controlled by a calibration reference voltage and energizing a calibration current generation resistor (452), said resistor and said reference voltage being constant for the duration of a calibration cycle.

8. The device as claimed in claim 7, characterized in that said calculation means perform at least some of the following operations:

measurement of the measurement voltage corresponding to the frequencies of the calibration current;

estimation of the calibration output voltage at the measurement frequency or frequencies;

determination of an estimate of an electrical quantity representative of said acquisition pathway;

determination of a relation between said estimate of said representative electrical quantity, said measurement voltage, said measurement current, said measurement resistance, said calibration resistance, said calibration current and said calibration reference voltage;

calculation of a 3×

3 matrix of the ratios of the measurement currents of said sensor to the measurement currents of said emitter.

9. The device as claimed in any one of claims 1 to 8, characterized in that said calculation means implement one at least of the elements of the group comprising:

polynomial interpolation;

multiple linear regression.

10. The device as claimed in any one of claims 3 to 9, characterized in that, in at least some of said at least two acquisition pathways, said measurement resistor is replaced with a single measurement resistor common to said at least some acquisition pathways.

12. The application of the device as claimed in any one of claims 1 to 9, or of the process as claimed in claim 10, to at least one of the following domains:

precision compasses used for measuring the magnetic heading in navigation;

servocontrolled fluxmeter sensors;

determination of the position and of the orientation of a mobile craft moving (translation and/or rotation) in a frame of reference, for example for a helmet viewfinder in aviation;

detection of magnetic masses in relative motion with respect to a sensor;

metrological measurements of magnetic fields;

measurements in a variable thermal environment.

11. A process for measuring magnetic field(s), implementing at least one measurement acquisition pathway comprising a measurement current generator, a coil, a measurement resistor, at least one amplifier, and at least one antialiasing filter delivering a measurement voltage,

characterized in that it implements:

a step of determination of at least one electrical quantity representative of said acquisition pathway, comprising a step of injection of a predetermined calibration current, comprising at least two frequency terms at at least two frequencies distinct from that (those) of said measurement current, said calibration current being superimposed on said measurement current,

a step of calculation delivering an estimate of said at least one electrical quantity at the frequency or frequencies of said measurement current.