Magnetic-based transducer for measuring displacement

• US 6,810,754 B2
• Filed: 02/24/2003
• Issued: 11/02/2004
• Est. Priority Date: 02/22/2002
• Status: Expired due to Term

• Current Assignee: Methode Electronics Incorporated
• Original Assignee: ABAS Inc. (Methode Electronics Incorporated)
• Inventors: May, Lutz Axel
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US10/373,634
• Publication Number:
  US 20040035221A1
• Time in Patent Office: 617 Days
• Field of Search: 738/623.31, 738/623.32, 738/623.33
• US Class Current: 73/862.333
• CPC Class Codes: G01D 5/14 influencing the magnitude of a current or voltage
• CPC Class Codes: G01D 5/2046 by a movable ferromagnetic element, e.g. a core
• CPC Class Codes: G01L 3/101 involving magnetic or electromagnetic means
• CPC Class Codes: G01L 3/105 involving inductive means G01L3/102, G01L3/104 take precedence

Abstract

A transducer for measuring displacement comprises a transducer assembly in which there is a coil wound about an axis and energisable to generate a magnetic field, and first and second magnetic field sensor devices, that are axially spaced with the coil therebetween, each device being in proximity to the coil to respond to a magnetic field component generated by energisation of the coil. A ferromagnetic member is disposed to interact with the field generated by the coil, the ferromagnetic member and the transducer assembly being mounted for relative displacement in the direction of said axis, such that the balance of the respective field components sensed by the first and second sensor devices is a function of the axial position of the ferromagnetic member relative to the transducer assembly.

Claims

1. A transducer for measuring displacement comprising:

a transducer assembly in which there is

a coil wound about an axis and energisable to generate a magnetic field, and first and second magnetic field sensor devices, that are axially spaced with coil therebetween, each device being in proximity to the coil to respond to a magnetic field component generated by energisation of the coil;

and a ferromagnetic member disposed to interact with the field generated by the coil,

the ferromagnetic member and the transducer assembly being mounted for relative displacement in the direction of said axis, such that the balance of the respective field components sensed by the first and second sensor devices is a function of the axial position of the ferromagnetic member relative to the transducer assembly.

2. A transducer as claimed in claim 1 in which said axis is linear and said

ferromagnetic member and said transducer assembly are mounted for a relative linear displacement.

3. A transducer as claimed in claim 1 in which a structure of ferromagnetic material is interposed between said member and said transducer assembly.

4. A transducer as claimed in claim 3 in which said structure is a tube, one of said transducer assembly and ferromagnetic member being mounted within the tube and the other being mounted exterior to the tube.

5. A transducer as claimed in claim 4 in which the ferromagnetic member is in the form of a ring and the member and the coil are disposed in proximity to the respective surface walls of the tube.

6. A transducer as claimed in claim 5 in which the ferromagnetic member and the transducer assembly are mounted exteriorly and interiorly of the tube respectively.

7. A transducer as claimed in claim 1 in which the ferromagnetic member is a part of or secured to move with a device whose displacement is to be measured.

8. A transducer as claimed in claim 1 further comprising an output circuit for developing a signal that is a function of relative displacement and to which said first and second sensor devices are connected in opposition so that the output signal represents the balance of the respective magnetic field components sensed thereby.

9. A transducer as claimed in claim 1 further comprising an A.C. source connected for energising said coil.

10. A transducer as claimed in claim 9 in which said A.C. source generates bipolar pulses of low duty cycle.

11. A transducer for measuring displacement comprising:

a transducer assembly in which there is

a first and a second coil each wound about an axis, the first and second coils being axially spaced and being interconnected for energisation such that the coils generate opposing fields in a region between the coils, and a magnetic field sensor device located in said region and responsive to the balance of the opposing fields generated therein;

and a ferromagnetic member disposed to interact with the magnetic fields generated in said region by the energised coils;

said ferromagnetic member and transducer assembly being mounted for relative displacement in the direction of said axis, such that the balance of opposing magnetic fields detected by said sensor device is a function of the axial position of the ferromagnetic member relative to the transducer assembly.

12. A transducer as claimed in claim 11 in which said axis is linear and said ferromagnetic member and said transducer assembly are mounted for a relative linear displacement.

13. A transducer as claimed in claim 11 in which a structure of ferromagnetic material is interposed between said member and said transducer assembly.

14. A transducer as claimed in claim 13 in which said structure is a tube, one of said transducer assembly and ferromagnetic member being mounted within the tube and the other being mounted exterior to the tube.

15. A transducer as claimed in claim 14 in which the ferromagnetic member is in the form of a ring and the member on the one hand and the first and second coils on the other hand are disposed in proximity to respective surface walls of the tube.

16. A transducer as claimed in claim 15 in which the ferromagnetic member and the transducer assembly are mounted exteriorly and interiorly of the tube respectively.

17. A transducer as claimed in claim 11 in which the ferromagnetic member is a part of or secured to move with a device whose displacement is to be measured.

18. A transducer as claimed in claim 11 further comprising an output circuit for developing a signal that is a function of relative displacement and to which said sensor device is connected so that the output signal represents the balance of the respective magnetic field components generated by the first and second coils.

19. A transducer as claimed in claim 11 further comprising an A.C. source connected for energising said coils.

20. A transducer as claimed in claim 19 in which said A.C. source generates bipolar pulses of low duty cycle.

21. A transducer as claimed in claim 19 in which said coils are connected in series to said source.