APPARATUS AND METHODS FOR PROXIMITY SENSING CIRCUITRY

• US 20090140728A1
• Filed: 11/29/2007
• Published: 06/04/2009
• Est. Priority Date: 11/29/2007
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Inventors: Rollins, George E., Kulkarni, Prachi S.
• Granted Patent: US 7,808,235 B2
• Time in Patent Office: Days
• US Class Current: 324/207.160
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence

Abstract

An inductive proximity sensor is disclosed. The proximity sensor includes a resonator with a bifurcated inductance coupled to a plurality of transimpedance amplifiers. A portion of the resonator is configured to generate eddy currents in a target containing metal. In various embodiments, the transimpedance amplifiers provide signals associated with eddy currents to a synchronous detector. Apparatus and methods for operating the inductive proximity sensor are disclosed.

Claims

1. A proximity sensor comprising:

a resonator having a bifurcated inductance, the bifurcated inductance including a reference portion and a target sensing portion;

a plurality of transimpedance amplifiers coupled to the resonator at the reference portion and the target sensing portion; and

a detector coupled to an output of the transimpedance amplifiers, wherein the detector is to provide a differential signal associated with an electromagnetic field interacting with a metal.

2. The sensor of claim 1, further comprising a reference signal generator coupled to an input of the resonator.

3. The sensor of claim 2, further comprising an inductive circuit to provide energy to the resonator.

4. The sensor of claim 1, wherein the resonator includes an attenuator in series with at least one of the reference portion and the target sensing portion.

5. The sensor of claim 1, wherein the detector is at least one of a synchronous detector and a quadrature detector.

6. The sensor of claim 1, wherein at least one of the plurality of transimpedance amplifiers is an operational amplifier.

7. The sensor of claim 1, wherein an inductive element associated with the target sensing portion is oriented orthogonal to an inductive element associated with the reference portion.

8. The sensor of claim 1, wherein one of the transimpedance amplifiers is coupled in series with the reference portion and another one of the transimpedance amplifiers is coupled in series with the target sensing portion.

9. The sensor of claim 1, wherein the target sensing portion is to generate eddy currents in a metal.

10. The sensor of claim 1, wherein the target sensing portion includes a current flowing through an inductive element that is used to determine proximity.

11. The sensor of claim 1, wherein an inductive element associated with the reference portion is at least one of shielded or isolated from a target metal.

12. A method of operating an inductive proximity sensor, the method comprising:

charging an inductive source to a steady state value;

initiating transfer of energy from the inductive source to a resonant circuit, the resonant circuit including a reference portion and a target sensing portion;

generating current oscillations in the reference portion and the target sensing portion;

sensing the current oscillations using a plurality of transimpedance amplifiers; and

generating a time dependent differential signal from signals provided by the transimpedance amplifiers and a reference signal generator.

13. The method of claim 12, wherein generating current oscillations includes generating current oscillations in the reference portion with an amplitude greater than or equal to an amplitude of the oscillations in the target sensing portion.

14. The method of claim 12, wherein generating current oscillations includes generating current oscillations in the reference portion with an amplitude less than an amplitude of the oscillations in the target sensing portion.

15. The method of claim 12, wherein sensing includes sensing using a reference signal associated with the transfer of energy.

16. The method of claim 12, wherein generating a time dependent differential signal includes generating a signal including phase information.

17. A dynamic control system comprising:

a processor;

an inductive proximity sensor coupled to the processor, the sensor including;

a source circuit comprising at least one of an inductive element and a step current source;

a resonator coupled to the source circuit, the resonator including an inductive portion having a reference portion and a target sensing portion;

a plurality of transimpedance amplifiers coupled to the resonator; and

a detector coupled to an output of the resonator to provide signals for determining proximity, and

wherein the inductive proximity sensor is configured to;

initiate transfer of energy from the source circuit to the resonant portion,

generate current oscillations in the reference portion and the target sensing portion;

sense the current oscillations using the plurality of transimpedance amplifiers; and

generate a time dependent differential signal from signals provided by the transimpedance amplifiers.

18. The system of claim 17, wherein the resonator includes an attenuator in series with at least one of the reference portion or the target sensing portion.

19. The system of claim 17, wherein the detector is at least one of a synchronous detector or a quadrature detector.

20. The system of claim 17, wherein an inductive element associated with the reference portion is at least one of oriented substantially orthogonal to an inductive element associated with the target sensing portion, shielded from a target metal and isolated from the target metal.

21. The system of claim 17, wherein one of the transimpedance amplifiers is coupled in series with the reference portion and another one of the transimpedance amplifiers is coupled in series with the target sensing portion.

22. The system of claim 17, wherein the target sensing portion is to generate eddy currents in a metal.