METHOD AND APPARATUS FOR CALIBRATION OF GAS AND LIQUID CONCENTRATION SENSORS WITHOUT THE NEED FOR KNOWN CALIBRATION STANDARDS
A device and method for calibrating a NO delivery device using NO and NO 2 measurements, without using a known standard.
1 . A method for tankless calibration of a nitric oxide (NO) sensor device comprising:
obtaining a gas in a closed volume, the gas including NO and oxygen, wherein the oxygen content exceeds the NO concentration;
measuring a change in NO signal and nitrogen dioxide (NO 2 ) signal by sampling the gas in the closed volume over a time frame;
calculating a rate of loss of NO signal and/or a rate of increase of the NO 2 signal,
determining whether the sum of the NO signal and the NO 2 signal is substantially constant over the time frame;
establishing the NO concentration from the rate of loss of NO signal; and
optionally, recalibrating the NO sensor according to the established NO concentration.
2 . The method of claim 1 wherein the time frame is about 15 to 30 seconds to 1 to 4 minutes.
3 . The method of claim 1 wherein the closed volume is between 0.5 and 1 liter of gas.
4 . The method of claim 1 wherein obtaining the gas in the closed volume includes filling the closed volume with the gas generated by a gas generation portion of the device.
5 . The method of claim 1 further comprising comparing the rate of loss of NO signal and/or the rate of increase of the NO 2 signal at two or more different NO starting concentrations, to determine that the rates vary by the square power of the starting NO concentration.
6 . The method of claim 1 , wherein the NO signal decreases by the same amount that the NO 2 signal increases.
7 . The method of claim 1 , wherein the oxygen content exceeds the NO concentration by at least a factor of 10.
8 . The method of claim 1 , wherein the oxygen content exceeds the NO concentration by at least a factor of 100,000.
9 . A method for confirming calibration of a nitric oxide (NO) sensor device comprising:
obtaining a gas in a closed volume, the gas including NO and oxygen, wherein the oxygen content is known;
measuring a change in NO concentration or nitrogen dioxide (NO 2 ) concentration by sampling the gas at a specific time after obtaining the gas;
calculating an original concentration of NO based on the specific time, the known oxygen content, and the measured NO concentration or the measured NO 2 concentration; and
determining whether the original concentration is accurate.