Optically powered sensor system with improved signal conditioning

• US 4,963,729 A
• Filed: 03/03/1989
• Issued: 10/16/1990
• Est. Priority Date: 03/03/1989
• Status: Expired due to Term

• Current Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Simmonds Precision Products, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Andresen, Richard P., Spillman, William B.
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): SHAMI, KHALED
• Application Number:
  US07/318,636
• Time in Patent Office: 592 Days
• Field of Search: 250/227, 250/551, 250/231 R, 455/612
• US Class Current: 250/227.21
• CPC Class Codes: G01D 5/12 using electric or magnetic means G01D5/06 takes precedence
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: G01F 23/266 measuring circuits therefor

Abstract

An optically powered sensor system with improved signal conditioning includes a plurality of sensors connected to a system optical bus that communicates with a system controller. Optical energy is transmitted along the bus for distribution to all sensor in the system with return pulses from the various sensors transmitted on the bus to the system controller. Each sensor includes a photodiode array for converting optical energy transmitted system-wide by the controller into electrical energy for storage in a storage capacitor associated with each sensor. A capacitance probe transducer and a fixed-value reference capacitor are connected to a resettable integrating pulse encoder that produces a series of short-duration pulses having a pulse spacing that is dependent upon the fixed value of the reference and the parameter-affected value of the transducer. The pulses are used to drive an optical source for transmitting optical pulses from the sensor to the system controller.

Claims

1. An optically powered sensor system comprising:

an optical energy source for transmitting optical energy;

an optical pathway for conveying the optical energy transmitted by said optical energy source;

at least one sensor connected to said optical pathway for receiving optical energy from said optical energy source, said sensor including means for converting optical energy from said optical pathway to electricity and storing the electrical energy, a transducer having a capacitive characteristic that varies as a function of a parameter to be sensed, a reference component having a capacitance value that is independent of the parameter to be measured, circuit means for providing electrical energy from said converting and storing means to said transducer and said reference component for selectively integrating the capacitance values of said transducer and reference component to produce a multi-pulse output having first time attribute that is a function of the capacitance of said transducer and a second time attribute that is a function of the capacitance of said reference component.

2. The optically powered sensor system of claim 1, wherein said circuit means produces at least a first set of two pulses, the interpulse spacing of which is a function of the capacitance of said transducer, and another set of pulses, the interpulse spacing of which is a function of the capacitance said reference component.

3. The optically powered sensor system of claim 1, wherein said circuit means produces at least a first set of two pulses, the interpulse spacing of which is a function of the combined capacitance of said transducer and said reference component, and another set of pulses, the interpulse spacing of which is a function of the capacitance said reference component.

4. The optically powered sensor system of claim 3, wherein the pulses of said first and second sets of pulses are fixed-duration pulses.

5. The optically powered sensor system of claim 1, wherein said circuit means comprises:

an integrator having a feedback path and first switching means for selectively switching said transducer and reference component into said feedback path.

6. The optically powered sensor system of claim 5, wherein said circuit means comprises:

second switching means for selectively shunting said feedback path.

7. The optically powered sensor system of claim 5, wherein said circuit means comprises:

means responsive to first and second values of the output of said integrator to produce pulse outputs at said values.

8. The optically powered sensor system of claim 7, wherein said circuit means comprises:

first and second comparators that switch output states at first and second values of the output of said integrator.

9. The optically powered sensor system of claim 8, wherein said circuit means comprises:

first and second pulse generators coupled, respectively, to said first and second comparators to produce pulse outputs at said first and second values.

10. The optically powered sensor system of claim 5, wherein said circuit means comprises:

timing and control means coupled to said first switching means to selectively (a) switch said transducer and reference component in parallel circuit into said feedback path and (b) switch said transducer into said feedback path.

11. The optically powered sensor system of claim 1, wherein said transducer comprises:

liquid level sensing probe.

12. The optically powered sensor system of claim 1, further comprising:

means for converting the pulse output of said circuit means to an optical pulse output.

13. The optically powered sensor system of claim 1, further comprising:

means for converting the pulse output of said circuit means to an optical pulse output and for introducing the optical pulse output onto said optical pathway.

14. An optically powered sensor comprising:

means for converting optical energy from an optical energy source to electricity and storing the electrical energy, a transducer having a capacitive characteristic that varies as a function of a parameter to be sensed, a reference component having a capacitance value that is independent of the parameter to be measured, circuit means for providing electrical energy from said converting and storing means to said transducer and said reference component for selectively integrating the capacitance values of said transducer and reference component to produce a multi-pulse output having first time attribute that is a function of the capacitance of said transducer and a second time attribute that is a function of the capacitance of said reference component.

15. The optically powered sensor of claim 14, wherein said circuit means produces at least a first set of two pulses, the interpulse spacing of which is a function of the capacitance of said transducer, and another set of pulses, the interpulse spacing of which is a function of the capacitance said reference component.

16. The optically powered sensor of claim 14, wherein said circuit means produces at least a first set of two pulses, the interpulse spacing of which is a function of the combined capacitance of said transducer and said reference component, and another set of pulses, the interpulse spacing of which is a function of the capacitance said reference component.

17. The optically powered sensor of claim 16, wherein the pulses of said first and second sets of pulses are fixed-duration pulses.

18. The optically powered sensor of claim 14, wherein said circuit means comprises:

an integrator having a feedback path and first switching means for selectively switching said transducer and reference component into said feedback path.

19. The optically powered sensor of claim 18, wherein said circuit means comprises:

second switching means for selectively shunting said feedback path.

20. The optically powered sensor of claim 18, wherein said circuit means comprises:

means responsive to first and second values of the output of said integrator to produce pulse outputs at said values.

21. The optically powered sensor of claim 20, wherein said circuit means comprises:

first and second comparators that switch output states at first and second values of the output of said integrator.

22. The optically powered sensor of claim 21, wherein said circuit means comprises:

first and second pulse generators coupled, respectively, to said first and second comparators to produce pulse outputs at said first and second values.

23. The optically powered sensor of claim 18, wherein said circuit means comprises:

timing and control means coupled to said first switching means to selectively (a) switch said transducer and reference component in parallel circuit into said feedback path and (b) switch said transducer into said feedback path.

24. The optically powered sensor of claim 14, wherein said transducer comprises:

liquid level sensing probe.

25. The optically powered sensor of claim 14, further comprising:

means for converting the pulse output of said circuit means to an optical pulse output.