Method and apparatus for calibration of gas and liquid concentration sensors without the need for known calibration standards

1. A method, comprising:

collecting a sample of a gas containing nitric oxide (NO) and oxygen in a container;

measuring a rate of a decrease in an NO signal over a period of time, the NO signal produced by a first electrochemical sensor based on a concentration of NO in the container;

determining based on the rate of the decrease in the NO signal, a concentration of NO in the gas at a time before any NO in the gas reacted with oxygen; and

adjusting a calibration parameter of the first electrochemical sensor based on the concentration of NO in the gas at the time before any NO in the gas reacted with oxygen.

2. The method of claim 1 , wherein:

the gas is a first gas; and

collecting the sample includes directing a second gas containing NO to the container, the second gas being devoid of oxygen and NO 2 , the method further comprising:

mixing the second gas within the container with a third gas to produce the first gas.

3. The method of claim 1 , wherein:

the gas is a first gas; and

collecting the sample includes directing a second gas containing NO to the container, the second gas being devoid of oxygen and NO 2 , the method further comprising:

mixing the second gas within the container with a third gas to produce the first gas at a first time, the first time being the time before any NO in the gas reacted with oxygen.

4. The method of claim 1 , wherein:

the gas is a first gas; and

collecting the sample includes directing a second gas containing NO to the container, the second gas being devoid of oxygen and NO 2 , the method further comprising; and

mixing a volume of the second gas within the container with a volume of a third gas to produce the first gas, the volume of the third gas being between 100 and 10,000 times larger than the volume of the second gas.

5. The method of claim 1 , wherein collecting the sample includes:

diverting a source gas to the container, the source gas containing NO at a concentration between 30 ppm and 80 ppm in air.

6. The method of claim 1 , further comprising:

measuring a rate of an increase in an NO 2 signal over the period of time, the NO 2 signal produced by a second electrochemical sensor based on a concentration of NO 2 in the container; and

determining based on the rate of the decrease in the NO signal and the rate of the increase in the NO 2 signal, the concentration of NO in the gas at the time before any NO in the gas reacted with oxygen.

7. The method of claim 6 , further comprising:

comparing a sum of the NO signal and the NO 2 signal; and

sending an indication of a calibration failure based on the sum of the NO signal and the NO 2 signal varying during the period of time.

8. The method of claim 1 , wherein the period of time is between 30 seconds and 4 min.

9. A method, comprising

collecting a sample of a gas containing nitric oxide (NO) and oxygen in a container;

measuring a rate of a decrease in an NO signal over a period of time, the NO signal produced by a first electrochemical sensor based on a concentration of NO in the container;

determining based on the rate of the decrease in the NO signal a concentration of NO in the gas; and

adjusting a calibration parameter of the first electrochemical sensor based on the concentration of NO in the gas.

10. The method of claim 9 , wherein:

the gas is a first gas; and

collecting the sample includes directing a second gas containing NO to the container, the second gas being devoid of oxygen and NO 2 , the method further comprising:

mixing the second gas within the container with a third gas to produce the first gas.

11. The method of claim 10 , wherein the concentration of NO in the gas is determined at a time when the second gas is mixed with the third gas and before any NO in the second gas has reacted with oxygen.

12. The method of claim 9 , wherein:

the gas is a first gas; and

collecting the sample includes directing a second gas containing NO to the container, the second gas being devoid of oxygen and NO 2 , the method further comprising; and

mixing a volume of the second gas within the container with a volume of a third gas to produce the first gas, the volume of the third gas being between 100 and 10,000 times larger than the volume of the second gas.

13. The method of claim 9 , wherein collecting the sample of NO includes:

diverting a source of gas to the container, the source of gas containing NO at a concentration between about 30 ppm to about 80 ppm.

14. The method of claim 9 , further comprising:

measuring a rate of an increase in an NO 2 signal over the period of time, the NO 2 signal produced by a second electrochemical sensor based on a concentration of NO 2 in the container; and

determining based on the rate of the decrease in the NO signal and the rate of the increase in the NO 2 signal, the concentration of NO in the gas.

15. The method of claim 14 , further comprising:

measuring a rate of an increase in an NO 2 signal over the period of time, the NO 2 signal produced by a second electrochemical sensor based on a concentration of NO 2 in the container;

determining based on the rate of the decrease in the NO signal and the rate of the increase in the NO 2 signal, the concentration of NO in the gas at the time before any NO in the gas reacted with oxygen.

16. The method of claim 9 , wherein the period of time is between about 30 seconds to about 4 min.

17. The method of claim 9 , further comprising:

measuring a rate of an increase in an NO 2 signal over the period of time, the NO 2 signal produced by a second electrochemical sensor based on a concentration of NO 2 in the container;

determining based on the rate of the decrease in the NO 2 signal, the concentration of NO 2 in the gas; and

adjusting a calibration parameter of the second electrochemical sensor based on the concentration of NO 2 in the gas.

18. A method, comprising

collecting a sample of a gas containing nitric oxide (NO) and oxygen in a container;

measuring a rate of an increase in an NO 2 signal over a period of time, the NO 2 signal produced by an electrochemical sensor based on a concentration of NO 2 in the container;

determining based on the rate of the increase in the NO 2 signal a concentration of NO 2 in the gas; and

adjusting a calibration parameter of the electrochemical sensor based on the concentration of NO 2 in the gas.

19. The method of claim 18 , wherein the electrochemical sensor is a first electrochemical sensor, the method further comprising:

measuring a rate of a decrease in an NO signal over the period of time, the NO signal produced by a second electrochemical sensor based on a concentration of NO in the container;

determining based on the rate of the increase in the NO signal, the concentration of NO in the gas; and

adjusting a calibration parameter of the second electrochemical sensor based on the concentration of NO in the gas.