Method and system for sensing gas incorporating an integrated reference element

1. A system for sensing hydrogen in a gas stream, the system comprising:

(a) a thermally conductive, electrically insulative substrate;

(b) a metal-gated metal-oxide semiconductor (MOS) gas-sensing element mounted on said substrate, said MOS gas-sensing element comprising a MOS gas sensing capacitor having a capacitance at a bias voltage, said MOS gas-sensing element capable of sensing said hydrogen in said gas stream;

(c) a metal-gated metal-oxide semiconductor (MOS) reference element mounted on said substrate, said MOS reference element comprising a MOS reference capacitor having a capacitance, said metal-gate comprising a metal that is inert with respect to said hydrogen in said gas stream, said MOS reference element and said MOS gas-sensing element having congruent electrical properties; and

(d) an electronic circuit interconnecting said MOS gas-sensing element and said MOS reference element, said circuit capable of actuating both of said elements, adjusting the bias voltage of said MOS gas-sensing capacitor to match the capacitance of said MOS gas-sensing capacitor with the capacitance of said MOS reference capacitor and driving said MOS reference capacitor and said MOS gas-sensing capacitor with complimentary AC waveforms signals that cancel when added together and having a control loop which drives the bias voltage of said MOS gas-sensing capacitor to maintain a minimum amplitude for a sum of outputs;

whereby a concentration of hydrogen in said gas stream has a proportional relationship to a change in the bias voltage.

2. The system of claim 1 wherein said MOS gas-sensing element comprises a material having electrical properties that change upon exposure to said hydrogen in said gas stream.

3. The system of claim 1 wherein the metal gate of said MOS gas-sensing element comprises a metal selected from the group consisting of palladium and a palladium alloy.

4. The system of claim 3 wherein said palladium alloy is selected from the group consisting of palladium/nickel, palladium/gold and palladium/silver.

5. The system of claim 1 wherein said inert metal is gold.

6. The system of claim 1 wherein said substrate comprises a silicon-containing material.

7. A method for sensing hydrogen in a gas stream comprising:

(a) mounting a metal-gated metal-oxide semiconductor (MOS) gas-sensing element on a thermally conductive, electrically insulative substrate, said MOS gas-sensing element comprising a MOS gas-sensing capacitor having a capacitance at a bias voltage, said MOS gas-sensing element capable of sensing said hydrogen in said gas stream;

(b) mounting a metal-gated metal-oxide semiconductor (MOS) reference element on said substrate, said MOS reference element comprising a MOS reference capacitor having a capacitance, said MOS reference element and said MOS gas-sensing element having congruent electrical properties, said MOS reference element insensitive to said hydrogen in said gas stream having essentially the same composition and conformation as said MOS gas-sensing element;

(c) interconnecting said MOS gas-sensing element and said MOS reference element in an electronic circuit;

(d) actuating both of said elements and adjusting the bias voltage on said MOS gas-sensing capacitor to match the capacitance of said MOS gas-sensing capacitor with the capacitance of said MOS reference capacitor and driving said MOS capacitor and said MOS gas-sensing capacitor with complimentary AC waveforms signals that cancel when added together and having a control loop which drives the bias voltage of said MOS gas-sensing capacitor to maintain a minimum amplitude for a sum of outputs, and

(e) measuring a change in the bias voltage of said electronic circuit, said change in the bias voltage having a proportional relationship to a concentration of said hydrogen in said gas stream.

8. A system for sensing hydrogen in a gas stream, the system comprising:

(a) a thermally conductive, electrically insulative substrate;

(b) a metal-gated metal-oxide semiconductor (MOS) gas-sensing element mounted on said substrate, said MOS gas-sensing element comprising a MOS gas-sensing capacitor having a capacitance at a bias voltage, said MOS gas-sensing element capable of sensing said hydrogen in said gas stream;

(c) a metal-gated metal-oxide semiconductor (MOS) reference element mounted on said substrate, said MOS reference element comprising a MOS reference capacitor having a capacitance, said metal gate comprising a passivated metal that is non-inert with respect to said hydrogen in said gas stream, said MOS reference element and said MOS gas-sensing element having congruent electrical properties; and

(d) an electronic circuit interconnecting said MOS gas-sensing element and said MOS reference element, said circuit capable of actuating both of said elements and adjusting the bias voltage of said MOS gas-sensing capacitor to match the capacitance of said MOS gas-sensing capacitor with the capacitance of said MOS reference capacitor and driving said MOS gas-sensing capacitor and said MOS reference capacitor with complimentary AC waveforms signals that cancel when added together and having a control loop which drives the bias voltage of said MOS gas-sensing element to maintain a minimum amplitude for a sum of outputs,

whereby a concentration of said hydrogen in said gas stream has a proportional relationship to a change in the bias voltage.

9. The system of claim 8 wherein each of said MOS gas-sensing element and said MOS reference element comprises a material having electrical properties that change upon exposure to said hydrogen in said gas stream.

10. The system of claim 8 wherein the metal gate of said MOS gas-sensing element comprises a metal selected from the group consisting of palladium and a palladium alloy.

11. The system of claim 10 wherein said palladium alloy is selected from the group consisting of palladium/nickel, palladium/gold and palladium/silver.

12. The system of claim 8 wherein said substrate comprises a silicon-containing material.