Sensing film material

• US 20050248356A1
• Filed: 06/16/2005
• Published: 11/10/2005
• Est. Priority Date: 01/11/2003
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Care, Ian C. D.
• Granted Patent: US 7,281,407 B2
• Time in Patent Office: Days
• US Class Current: 324/686
• CPC Class Codes: G01B 7/06 for measuring thickness measuring during the manufacture of coatings C23C14/54
• CPC Class Codes: G01M 3/025 Details with respect to the testing of engines or engine parts
• CPC Class Codes: G01M 3/16 using electric detection means G01M3/045, G01M3/06, G01M3/12, G01M3/20, G01M3/24, G01M3/26 take precedence
• CPC Class Codes: G01M 3/186 for containers, e.g. radiators
• CPC Class Codes: G01N 27/07 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 27/226 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 33/28 Oils , i.e. hydrocarbon liquidsgaseous fuels G01N33/225; edible oils or edible fats G01N33/03

Abstract

A sensor 30 has first and second electrodes 32A, 32B spaced to define a gap 34 therebetween. The electrodes are formed on a substrate which can be covered with a film of material. The width of the gap 34 is different at different positions on the electrodes 32. This results in a sensing characteristic which can be made substantially linear, without sensitivity varying with film thickness, which arises from the use of a constant gap width. The sensor can be used to detect or measure film or liquid layer thickness, or solid material deposition.

Claims

1. A sensor (30) for sensing a property of a film of material, the sensor (30) comprising first and second electrodes spaced to define a gap (34) therebetween, the film of material being located within the gap (34), during use, characterised in that the width of the gap (34) is different at different positions on the electrode members whereby the sensing characteristics of the sensor (30) are different at different positions on the electrode members.

2. A sensor (30) according to claim 1, wherein the width of the gap (34) varies substantially continuously.

3. A sensor (30) according to claim 1, wherein the width of the gap (34) changes in step fashion at one or more discontinuities.

4. A sensor (30) according to claim 1, wherein the width of the gap (34) varies to create a substantially linear output characteristic for the sensor (30), in response to changes in the property being sensed.

5. A sensor (30) according to claim 1, wherein the electrodes are generally elongate.

6. A sensor (30) according to claim 1, wherein the electrodes are interdigitated fingers, the gap (34) width being different at different positions along each finger.

7. A sensor (30) according to claim 6, wherein the interdigitated fingers form a repeating pattern.

8. A sensor (30) according to any of claims 1 to claim 1, wherein the electrodes are generally curved to define a curved gap (34) therebetween.

9. A sensor (30) according to claim 8, wherein the electrodes form inner and outer closed curves, the gap (34) forming a continuous curve therebetween.

10. A sensor (30) according to claim 1, wherein the thickness of at least one electrode is different at different positions on the electrode.

11. A sensor (30) according to claim 1, wherein the electrodes are mounted to be adjustably positioned relative to one another, to allow the gap (34) widths to be changed.

12. A sensor (30) according to claim 1, further comprising control means operable to take measurements from the electrodes, across the gap (34), and to deduce the film property therefrom.

13. A sensor (30) according to claim 12, wherein the control means is operable at a plurality of frequencies.

14. A sensor (30) according to claim 13, wherein the or one of the operating frequencies of the voltage source is DC.

15. A sensor (30) according to claim 13, wherein the control means is operable to combine measurements to eliminate at least one frequency-dependent component of the property being sensed.

16. A sensor (30) according to claim 1, wherein the control means is operable to sense one or more of the resistance, reactance, capacitance, conductance or impedance between the electrodes.

17. A machine incorporating a sensor (30) as aforesaid.

18. A machine according to claim 17, wherein the sensor (30) is formed at a surface of the machine, the film of material being on the surface, during use of the machine, whereby the sensor (30) is covered by the film, which spans the gap (34).