Heated electrode refrigerant detector utilizing one or more control loop

• US 6,644,098 B2
• Filed: 04/19/2001
• Issued: 11/11/2003
• Est. Priority Date: 01/18/2001
• Status: Active Grant

• Current Assignee: SPX Corporation
• Original Assignee: Advanced Test Products, Inc. (SPX Corporation)
• Inventors: Zubik, Robert, Cardinale, Dennis
• Primary Examiner(s): Kwok, Helen
• Assistant Examiner(s): WIGGINS, JOHN DAVID
• Application Number:
  US09/838,169
• Publication Number:
  US 20020092341A1
• Time in Patent Office: 936 Days
• Field of Search: 73/250.1, 73/250.5, 73/232, 73/310.5, 422/98, 422/90, 422/109, 324/98, 324/109, 324/610, 324/464, 324/443-444
• US Class Current: 73/25.01
• CPC Class Codes: G01N 27/12 of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid , for detecting components in the fluid

Abstract

A gas detector for sensing the presence of at least one predetermined gas is operative in conjunction with a electrical power source and includes a detection circuit, a temperature controller, and a electrical current controller, wherein the detection circuit includes a sensing device having first and second electrodes, the first electrode being connected to the power source for heating the first electrode, the temperature controller is operatively connectable to the detection circuit for maintaining a temperature of the first electrode at a predetermined magnitude, and the current controller is operatively connectable to the detection circuit for maintaining a current in the second electrode at a predetermined magnitude.

Claims

1. A gas detector, operative in conjunction with a power source, for sensing the presence of at least one predetermined gas, the gas detector comprising:

a detection circuit, the detection circuit including a sensing device having first and second electrodes, wherein the first electrode is connected to the power source for heating the first electrode;

a temperature controller operatively connectable to the detection circuit for maintaining a temperature of the first electrode at a predetermined magnitude;

a current controller operatively connectable to the detection circuit for maintaining a electrical current in the second electrode at a predetermined magnitude; and

a switch adjustable between at least two positions, wherein in a first switch position the temperature controller is operatively connected to the detection circuit and in a second switch position the current controller is operatively connected to the detection circuit, the position of the switch is determined on the basis of an operating condition of the gas detector.

2. The gas detector as in claim 1, wherein the switch is located internally to the gas detector.

3. The gas detector as in claim 1, wherein the switch is located externally on the gas detector.

4. A method of controlling a gas detector for sensing the presence of at least one predetermined gas, the gas detector having a heated first electrode and a second electrode, herein the method comprises the steps of:

heating the first electrode to a predetermined absolute temperature;

upon reaching the predetermined absolute temperature, placing the electrodes in a test location;

upon being exposed to one of the predetermined gases, generating an increased electrical current in the second electrode; and

maintaining the first electrode at substantially the predetermined absolute temperature while placing the electrodes in the test location and while generating the increased current.

5. The method of claim 4, further including the steps of selecting the predetermined absolute temperature and providing an indication of the predetermined absolute temperature to the gas detector.

6. The method of claim 5, wherein the step of providing an indication of the predetermined absolute temperature takes place while the detector is being operated.

7. The method of claim 5, wherein the step of providing an indication of the predetermined absolute temperature includes the step of predefining the predetermined absolute temperature during manufacturing.

8. The method of claim 5, wherein the step of providing an indication of the predetermined absolute temperature includes the step of entering the predetermined absolute temperature into the gas detector.

9. The method of claim 4, wherein the amount of heat applied to the first electrode is dependent on a duty cycle, and wherein the step of maintaining the first electrode at substantially the predetermined absolute temperature includes the step of adjusting the duty cycle.

10. The method of claim 4, further including the step of monitoring the actual temperature of the first electrode, and wherein the step of maintaining the first electrode at substantially the predetermined absolute temperature includes the steps of reducing the temperature of the first electrode upon determining that the actual temperature exceeds the predetermined absolute temperature and raising the temperature of the first electrode upon determining that the actual temperature is below the predetermined absolute temperature.

11. A gas detector, operative in conjunction with a power source, for sensing the presence of at least one predetermined gas, the gas detector comprising:

an anode/cathode assembly coated with a ceramic material, the anode/cathode assembly including a cathode wire and an anode wire at least partly surrounding the cathode wire, wherein the anode wire has opposing ends and wherein one of the anode wire ends is electrically connected to the power source;

a pair of supply contacts electrically connected to the respective ends of the anode wire;

a pair of temperature sense contacts electrically connected to respective ends of the anode wire;

a cathode contact electrically connected to an end of the cathode wire;

a temperature-sensing circuit electrically connected to at least one of the temperature sense contacts for monitoring the temperature of the anode/cathode assembly; and

a bias current-sensing circuit electrically connected to the cathode contact.

12. A system for controlling a gas detector for sensing the presence of at least one predetermined gas, the gas detector having a heated first electrode and a second heated electrode, comprising:

means for heating the first electrode to a predetermined absolute temperature;

means for placing the electrodes in a test location;

means for generating an increased electrical current in the second electrode; and

means for maintaining the first electrode at substantially the predetermined absolute temperature while placing the electrodes in the test location and while generating the increased current.

13. The system as in claim 12, further comprising means for selecting the predetermined absolute temperature and means for indicating the predetermined absolute temperature of the gas detector.

14. The system as in claim 13, wherein the means for providing the indication of the predetermined absolute temperature while the detector is being operated.

15. The system as in claim 13, wherein the means for providing the indication of the predetermined absolute temperature includes a predefined absolute temperature.

16. The system as in claim 15, wherein the predefined absolute temperature is determined at the time of manufacturer.

17. The system as in claim 13, further comprising means for entering the predetermined absolute temperature into the gas detector.

18. The system as in claim 12, wherein the amount of heat applied to the first electrode is dependent on a duty cycle and wherein the means for maintaining the first electrode at substantially the predetermined absolute temperature comprises means for adjusting a duty cycle.

19. The system of claim 12, further comprising means for monitoring the temperature of the actual temperature of the first electrode, means for reducing the temperature of the first electrode upon determining that the actual temperature exceeds the predetermined absolute temperature and means for raising the temperature of the first electrode upon determining that the actual temperature is below the predetermined absolute temperature.

20. The gas detector as in claim 19, wherein the internal switch is implemented with discrete components.