Fiberoptic temperature/pressure sensor system

• US 4,672,199 A
• Filed: 03/02/1984
• Issued: 06/09/1987
• Est. Priority Date: 03/02/1984
• Status: Expired due to Fees

• Current Assignee: Fiber Dynamics, Inc. (Évora SA)
• Original Assignee: Fiber Dynamics, Inc. (Évora SA)
• Inventors: Lamb, Archie C., Anderson, John C., Davies, Morris J.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US06/585,430
• Time in Patent Office: 1,194 Days
• Field of Search: 250/227, 250/231 R, 374/19, 374/161, 374/162, 374/205, 374/121
• US Class Current: 250/227.21
• CPC Class Codes: G01D 5/268 using optical fibres G01D5/28 - G01D5/38 take precedence
• CPC Class Codes: G01K 5/72 with electric transmission means for final indication
• CPC Class Codes: G01L 11/02 by optical means
• CPC Class Codes: G01L 9/0089 Transmitting or indicating the displacement of pistons by electrical, electromechanical, magnetic or electromagnetic means G01L9/0008 takes precedence
• CPC Class Codes: G02B 6/3624 Fibre head, e.g. fibre probe termination optical details of light guide terminations G02B6/241; reshaping of light guides G02B6/2552; optical details of coupling light into or out of fibre end G02B6/262

Abstract

A fiberoptic sensing system comprising a light source, a sensor responsive to external stimulus, an optical fiber connected to the light source and the sensor, a detector arranged to receive light from the optical fiber, and output electronics electrically connected to the detector. The sensor includes a reflective surface arranged so as to reflect light from the optical fiber. This reflective surface is movable relative to the optical fiber. The light source comprises a light-emitting diode and a reference diode electrically connected to the source of electrical energy and to the light-emitting diode. A beamsplitter is disposed about the light source, the optical fiber, and the photodetector. The detector includes a transimpedance amplifier and a RMS to DC converter. The output electronics includes a gain control and a offset control. The sensor may be either a temperature sensor or a pressure sensor.

Claims

1. A fiberoptic sensing system comprising:

a light source means;

temperature sensor means responsive to an external stimulus, said temperature sensor means comprising;

a housing;

a carrier arranged within said housing, said carrier having a reflective surface thereto; and

a temperature-sensitive member connected to said carrier at one end and anchored to said housing at the other end, said temperature-sensitive member causing said carrier to move within said housing responsive to changes in temperature affecting said temperature-sensitive member, said temperaturesensitive member comprising;

a first bimetallic strip having an inner metallic portion and an outer metallic portion, and

a second bimetallic strip having an inner metallic portion and an outer metallic portion, said first and second bimetallic strips arranged in plane parallel to each other within said housing, said inner metallic portions of said first and second bimetallic strips having a higher coefficient of thermal expansion than said outer metallic portions of said first and second bimetallic strips;

fiberoptic means for transmitting light from said light source means to said temperature sensor means, said reflective surface for reflecting light from said fiberoptic means back into said fiberoptic means, said temperature-sensitive member causing said carrier to change in distance between said fiberoptic means and said reflective surface in a direction perpendicular to said reflective surface;

detector means arranged so as to receive the light reflected by said reflective surface of said temperature sensor means through said fiberoptic means, said detector means being responsive to the intensity of light from said fiberoptic means; and

output means electrically connected to said detector means for producing a signal relative to the light as received by said detector means,

2. The apparatus of claim 1, said light source means comprising:

a light-emitting diode; and

current stabilizing means electrically connected to a source of electrical energy and to said light-emitting diode for stabilizing current to said light-emitting diode.

3. The apparatus of claim 2, said current stabilizing means comprising:

a Zener diode circuit;

an operational amplifier electrically connected to said Zener diode circuit; and

a potentiometer electrically associated with said Zener diode circuit and said operational amplifier and said light-emitting diode, said potentiometer for setting the power level to said light-emitting diode.

4. The apparatus of claim 1, said temperature sensor means further comprising:

fiberoptic connection means attached to one end of said housing, said fiberoptic connection means arranged such that the longitudinal axis of the end of said fiberoptic means passing therethrough is positioned in perpendicular relationship to said reflective surface.

5. The apparatus of claim 1, said fiberoptic means comprising a single optical fiber from said light source means to said sensor means.

6. The apparatus of claim 1, further comprising beamsplitter means disposed about said light source means, said fiberoptic means and said detector means, said beamsplitter means for passing light from said light source means to said fiberoptic means and passing said light from said fiberoptic means to said detector means.

7. The apparatus of claim 1, said detector means comprising a photodetector positioned relative to said fiberoptic means so as to be electrically responsive to light emitted by said fiberoptic means for producing a current relative to the intensity of the light from said fiberoptic means.

8. A fiberoptic temperature sensor comprising:

a housing;

a carrier arranged within said housing, said carrier having a reflective surface affixed thereto;

a temperature-sensitive member connected to said carrier at one end and anchored to said housing at the other end, said temperature-sensitive member causing said carrier to move within said housing in response to changes in temperature affecting said temperature-sensitive member, said temperature-sensitive member comprising;

a first bimetallic strip having an inner metallic portion and an outer metallic portion; and

a second bimetallic strip having an inner metallic portion and an outer metallic portion, said first and second bimetallic strips arranged in plane parallel to each other within said housing, said inner metallic portions of said first and second bimetallic strips having a higher coefficient of thermal expansion than said outer metallic portions of said first and second bimetallic strips; and

fiberoptic connection means attached to said housing so as to permit the attachment of at least one optical fiber so that the end of said optical fiber is perpendicular to said reflective surface, said temperature sensitive member causing said carrier to change in distance between said fiberoptic connection means and said reflective surface in a direction perpendicular to said reflective surface.