Target sensor

• US 9,030,212 B2
• Filed: 09/28/2012
• Issued: 05/12/2015
• Est. Priority Date: 09/28/2011
• Status: Active Grant

• Current Assignee: Salunda Limited
• Original Assignee: Salunda Limited
• Inventors: Karenowska, Alexy Davison, Wherritt, Peter, Harrison, Martin Roy, Gregg, John Francis
• Primary Examiner(s): Vazquez, Arleen M
• Assistant Examiner(s): HAWKINS, DOMINIC E
• Application Number:
  US13/630,880
• Publication Number:
  US 20130076373A1
• Time in Patent Office: 956 Days
• Field of Search: 324/603, 324/602
• US Class Current: 324/603
• CPC Class Codes: F01D 21/003 Arrangements for testing or measuring for measuring vibrations G01H
• CPC Class Codes: F01D 21/04 responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position
• CPC Class Codes: F05D 2260/80 Diagnostics
• CPC Class Codes: F05D 2270/804 Optical devices
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: H03K 17/9545 with variable frequency
• CPC Class Codes: H03K 2017/9527 Details of coils in the emitter or receiver; Magnetic detector comprising emitting and receiving coils

Abstract

Target sensor comprising: sensor probe having a resonance frequency that changes as the separation of the sensor probe and a target changes. Oscillator arranged to apply a radio frequency (RF) signal to the sensor probe, the oscillator having: control circuitry configured to regulate the frequency of the RF signal applied to the sensor probe to below the resonance frequency of the sensor probe. Detector arranged to detect an electrical characteristic of the oscillator that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target.

Claims

1. A target sensor comprising:

a sensor probe having a resonance frequency that changes as the separation of the sensor probe and a target changes;

an oscillator arranged to apply a radio frequency (RF) signal to the sensor probe, the oscillator having;

control circuitry configured to regulate the frequency of the RF signal applied to the sensor probe to a regulated frequency which is, both in the presence and absence of interaction between the sensor probe and a target, simultaneously;

(a) not less than ω

₀/Q below the resonance frequency ω

₀ of the sensor probe (Q being the quality factor of the sensor probe), and (b) not below the frequency ω

_L=R*/L where R* is the sum of the source impedance from which the sensor probe is driven and its resistance, and L is its inductance; and

a detector arranged to detect an electrical characteristic of the oscillator that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target.

2. The target sensor of claim 1 further comprising a circuit arranged to determine the resonance frequency of the sensor probe.

3. The target sensor of claim 1, wherein the control circuitry is further configured to regulate the frequency of the RF signal to a constant frequency.

4. The target sensor according to claim 1, wherein the detector is an amplitude modulation detector.

5. The target sensor according to claim 1, wherein the electrical characteristic is selected from the group consisting of:

frequency;

amplitude;

quality factor, Q;

current; and

voltage.

6. The target sensor according to claim 1, wherein the control circuitry is configured to regulate the applied RF signal between 1% and 25% below the resonance frequency of the sensor probe.

7. The target sensor according to claim 1, wherein the control circuitry is configured to regulate the applied RF signal between 100 KHz and 400 MHz.

8. The target sensor according to claim 1, wherein the detector is further arranged to indicate target clearance from the change in impedance.

9. The target sensor according to claim 1, wherein the detector is further arranged to indicate that the target clearance is within a range of clearances.

10. The target sensor according claim 1, wherein the detector further detects the real and imaginary components of the impedance of the sensor probe.

11. The target sensor according to claim 1 further comprising a validation circuit configured to apply a DC continuity current to the sensor probe.

12. The target sensor according to claim 1 in which the target is selected from the group consisting of:

rotor blade, rotor, surface, conductive surface, pipe, gas pipe, oil pipe, water pipe, tubing or well casing.

13. The target sensor according to claim 1 wherein the target sensor is used within an aero engine.

14. A system comprising:

a plurality of target sensors each comprising;

a sensor probe having a resonance frequency that changes as the separation of the sensor probe and a target changes;

an oscillator arranged to apply a radio frequency (RF) signal to the sensor probe, the oscillator having;

control circuitry configured to regulate the frequency of the RF signal applied to the sensor probe to a regulated frequency which is, both in the presence and absence of interaction between the sensor probe and a target, simultaneously;

(a) not less than ω

₀/Q below the resonance frequency ω

₀ of the sensor probe (Q being the quality factor of the sensor probe), and (b) not below the frequency ω

_L=R*/L where R* is the sum of the source impedance from which the sensor probe is driven and its resistance, and L is its inductance; and

a detector arranged to detect an electrical characteristic of the oscillator that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target; and

a single transmission line configured to provide an electrical connection between each sensor probe and its corresponding oscillator, wherein each oscillator is configured to drive its corresponding target sensor at a different frequency.

15. The system of claim 14 further comprising a multiplexor arranged to maintain the electrical connection within the single transmission line.

16. A method of sensing a target comprising the steps of:

providing a sensor probe having a resonance frequency that changes as the separation of the sensor probe and the target changes;

driving the sensor probe with a radio frequency, RF, signal regulated to a regulated frequency which is, both in the presence and absence of interaction between the sensor probe and a target, simultaneously;

(a) not less than ω

₀/Q below the resonance frequency ω

₀ of the sensor probe (Q being the quality factor of the sensor probe), below the frequency ω

_L=R*/L where R* is the sum of the source impedance from which the sensor probe is driven and its resistance, and L is its inductance; and

detecting an electrical characteristic that varies with the impedance of the sensor probe indicating an interaction of the sensor probe with the target such that the target is sensed.

17. The method of claim 16, wherein the RF signal is regulated to a constant frequency.

18. The method of claim 16, wherein detecting the electrical characteristic further comprises detecting changes in amplitude of the RF signal at the regulated frequency.