Apparatus and method of measuring the multi-dimensional magnetic field distribution of a magnetic sample in real-time

• US 6,611,142 B1
• Filed: 01/28/2000
• Issued: 08/26/2003
• Est. Priority Date: 04/01/1997
• Status: Expired due to Fees

• Current Assignee: Redcliffe Limited
• Original Assignee: Redcliffe Limited
• Inventors: Nicholson, Pascual Ian, Cox, Paul Gerald, Jones, David Geraint Rhys
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US09/402,106
• Time in Patent Office: 1,306 Days
• Field of Search: 324/205, 324/211, 324/219, 324/220, 324/226, 324/227, 324/235, 324/244, 324/247, 324/248, 324/251, 324/252, 324/261, 324/262, 324/263
• US Class Current: 324/261
• CPC Class Codes: G01R 33/10 Plotting field distribution ; Measuring field distribution

Abstract

An apparatus for measuring the magnetic field distribution of a magnetic sample includes a magnetic field sensor arrangement having three, orthogonally-disposed, Hall sensors for sensing the magnetic field produced by a magnetic sample at a given location, The sensor arrangement is scanned along a predetermined scan pattern. The apparatus then acquires sampling data from the sensor arrangement, the sampled data providing a representation of the magnetic field distribution of the magnetic sample. The data is preferably acquired by an interface card for a PC, which stores sampled data in the main memory of the PC for data analysis and display.

Claims

1. An apparatus for determining the magnetic field distribution of a magnetic sample, the apparatus comprising:

magnetic field sensing means for sensing the magnetic field produced by the sample at a given location, said magnetic field sensing means comprising a sensing head having a plurality of magnetic sensors arranged to sense magnetic field strength in plural orthogonal directions;

scanning means arranged to effect area scanning of said magnetic sample by movement of said sensing head relative to the sample along a predetermined scan pattern, said scanning means making sub-millimeter positional movements of said sensing head and thus achieving a correspondingly high resolution of the magnetic field distribution determined by the apparatus;

data acquisition means coupled to said magnetic field sensing means and to said scanning means, said data acquisition means-being dedicated to the processing of signals outputted by said sensors and to the control of said scanning means and comprising analog-to-digital signal conversion means coupled to said sensors for converting the analog outputs thereof into corresponding digital signals;

storage means for storing said digital signals;

a microprocessor controlling the operation of said analog-to-digital signal conversion means and the storage of said digital signals in said storage means, said microprocessor additionally controlling the operation of said scanning means in coordination with said analog-to-digital signal conversion means and said storage means; and

computer means including display means, said computer means being arranged to receive digital data from the storage means of said data acquisition means under control of said microprocessor, to process said digital data into user understandable magnetic field maps, and to display said magnetic field maps upon said display means,

wherein the scanning means comprises a robot assembly to which said sensing means is coupled, said robot assembly including first means for moving said sensing means in one coordinate dimension, and second means for effecting relative rotation between the sample and the sensing means.

2. An apparatus according to claim 1, wherein the data acquisition means is arranged to carry out data acquisition and to store the digital data in said storage means in real time.

3. An apparatus according to claim 1, wherein said storage means provides a temporary storage and said data acquisition means is arranged to carry out a direct memory access to a main storage means to which the data acquisition means is connected.

4. An apparatus according to claim 1, further comprising a program storage means for storing a program for controlling the microprocessor to carry out data acquisition.

5. An apparatus according to claim 1, wherein the data acquisition means includes means for checking the status of the scanning means and the sensing means to ensure that the apparatus is only operated under predetermined status conditions.

6. An apparatus according to claim 1, wherein said magnetic field sensing means and said data acquisition means are arranged to sense the magnetic field of the magnetic sample in three orthogonal directions and to obtain a three-dimensional representation of the magnetic field.

7. An apparatus according to claim 1, wherein said computer means is arranged to provide a false color image display format.

8. An apparatus according to claim 1, wherein said computer means includes means for analyzing the data from the data acquisition means to determine magnetic force vectors and/or lines of force and for superimposing such vectors and/or lines of force on the displayed magnetic field map.

9. An apparatus according to claim 1, wherein said computer means includes means for analyzing the data from the data acquisition means to provide a magnetic field strength cross-section through a user selectable position on the magnetic field map.

10. An apparatus according to claim 1 wherein the scanning means comprises a robot assembly to which said sensing means is coupled, said robot assembly including first means for moving said sensing means in one coordinate dimension, and second means for moving the sensing means in another coordinate dimension transverse to said one coordinate dimension.

11. An apparatus according to claim 1 wherein said sensing means comprises a head with a plurality of sensors spaced-apart along a scan line, each sensor sensing magnetic field strength in a different direction than the other sensors, the sensing means being arranged to be moved along said scan line during a scanning operation such that each sensor can sense the magnetic field in its direction at any given location.

12. An apparatus according to claim 11, wherein each of said plurality of sensors is a Hall Effect sensor.

13. The apparatus of claim 1, wherein said scanning means comprises a scanner robot assembly.

14. The apparatus of claim 1, wherein said scanning means comprises an X-Y flatbed device.

15. The apparatus of claim 1, wherein said scanning means effects area scanning of the magnetic sample by stepwise movement of the sensing head by a step size of 0.1 mm.

16. The apparatus of claim 1, wherein said scanning means effects area scanning of the magnetic sample by stepwise movement of the sensing head by a step size in the range of 0.1 to 10.0 mm.

17. The apparatus of claim 1, wherein said scanning means effects area scanning of the magnetic sample by stepwise movement of the sensing head by a step size selected from the group consisting of 0.1 mm, 0.2 mm, 1.0 mm, 5.0 mm, and 10.0 mm.

18. A magnetic field scanner for measuring the magnetic field distribution of a magnetic sample in a curved plane about the sample, the scanner comprising:

magnetic field sensing means for sensing the magnetic field produced by the magnetic sample in a plurality of directions at a given location along the curved plane; and

scanning means comprising rotation means and linear movement means, said rotation and linear movement means being operable on at least one of said sample or sensing means to provide both linear and rotational relative movement between the sample and the magnetic field sensing means in use,

wherein the magnetic field sensing means comprises an elongate probe for insertion into an inner region of a hollow cylindrically shaped magnetic sample, the probe having at least one sensor provided at a free insertion end thereof.

19. A magnetic field scanner according to claim 18, wherein the rotation means is operable on the sample and the linear movement means is operable on the sensing means.

20. A magnetic field scanner according to claim 19, wherein the rotation means comprises a means for retaining the magnetic sample and means for rotating the retaining means and the magnetic sample together.

21. A magnetic field scanner according to claim 20, wherein the rotation means comprises a stepper motor with a rotary output and a free bearing, the retaining means and magnetic sample being provided between the rotation means and the free bearing.

22. A magnetic field scanner according to claim 20, wherein the retaining means comprises at least one chuck mechanism and at least one adaptor, said at least one adaptor being securable in a respective one of said at least one chuck mechanisms and being arranged to be releasably secured to an end of said magnetic sample.

23. A magnetic field scanner according to claim 18 wherein the magnetic field sensing means comprises a plurality of spaced apart Hall Effect sensors.

24. A magnetic field measuring apparatus incorporating a magnetic field scanner according to claim 18 wherein the apparatus is arranged to display data obtained from the scanner in a polar coordinate magnetic field map.