Method and apparatus for determining the concentration of a gas
First Claim
1. A method for determining the concentration of a known type gas present in a gas sample mixture comprising:
- (a) providing light through a chamber;
(b) introducing the gas sample mixture into the chamber;
(c) detecting light in the chamber and producing an electric output signal which is a function of the amount of light detected;
(d) measuring the output signal for three sequential instantaneous periods of time t1, t2, t3 ;
(e) determining the relative difference between the output signals at t1 and the output signal at t2 which gives a change of output signal value CS1 ;
(f) determining the relative difference between the output signal at t2 and the output signal at t3 which gives a change of output signal value CS2 ;
(g) determining the relative difference between the change of output signal value CS1 and the change of output signal value CS2 which gives a change of the change of the output signal value CCS1 ;
(h) repeating the method steps of (d) through (g) to develop a plurality of CCS data which generates a pattern; and
(i) comparing the CCS data of step (h) to corresponding CCS data for the known type of gas at a range of known concentrations and at a range of known temperatures to determine the concentration of the known type gas in the sample mixture contained in the chamber.
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Abstract
A method and apparatus for determining the concentration of a gas using nondispersive infrared absorption. The method includes measuring the output signal for a plurality of instantaneous time periods, calculating the change of the output signals (CS), calculating the change of the change of the output signal (CCS) which creates a pattern of CCS data and comparing the CCS data with corresponding CCS data for a known reference gas at a known concentration and at a range of known temperatures. The apparatus for determining the concentration of a known gas in a sample gas mixture is a gas chamber, a light source, a detector, a signal converter, and a data acquisition and microprocessor unit which measures the output signal and has a memory with a program to calculate the change of the signal (CS) and the change of the change of the signal (CCS), and compare the CCS data generated from the gas sample mixture to CCS data of known gases with known concentrations and at known temperature ranges.
68 Citations
16 Claims
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1. A method for determining the concentration of a known type gas present in a gas sample mixture comprising:
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(a) providing light through a chamber; (b) introducing the gas sample mixture into the chamber; (c) detecting light in the chamber and producing an electric output signal which is a function of the amount of light detected; (d) measuring the output signal for three sequential instantaneous periods of time t1, t2, t3 ; (e) determining the relative difference between the output signals at t1 and the output signal at t2 which gives a change of output signal value CS1 ; (f) determining the relative difference between the output signal at t2 and the output signal at t3 which gives a change of output signal value CS2 ; (g) determining the relative difference between the change of output signal value CS1 and the change of output signal value CS2 which gives a change of the change of the output signal value CCS1 ; (h) repeating the method steps of (d) through (g) to develop a plurality of CCS data which generates a pattern; and (i) comparing the CCS data of step (h) to corresponding CCS data for the known type of gas at a range of known concentrations and at a range of known temperatures to determine the concentration of the known type gas in the sample mixture contained in the chamber.
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2. A method for determining the concentration of a known type gas present in a gas sample mixture comprising:
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(a) providing light through a chamber; (b) introducing the gas sample mixture into the chamber; (c) detecting light in the chamber and producing an electric output signal which is a function of the amount of light detected; (d) measuring the output signal for four sequential instantaneous periods of time t1, t2, t3, t4 ; (e) determining the relative difference between the output signals at t1 and the output signal at t2 which gives a change of output signal value CS1 ; (f) determining the relative difference between the output signal at t3 and the output signal at t4 which gives a change of output signal value CS2 ; (g) determining the relative difference between the change of output signal value CS1 and the change of output signal value CS2 which gives a change of the change of the output signal value CCS1 ; (h) repeating the method steps of (d) through (g) to develop a plurality of CCS data which generates a pattern; and (i) comparing the CCS data of step (h) to corresponding CCS data for the known type of gas at a range of known concentrations and at a range of known temperatures to determine the concentration of the known type gas in the sample mixture contained in the chamber.
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3. A method for determining the concentration of a known type gas present in a gas sample mixture comprising:
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(a) providing light through a chamber; (b) introducing the gas sample mixture into the chamber; (c) detecting light in the chamber and producing an electric output signal which is a function of the amount of light detected; (d) measuring the output signal for a first instantaneous period of time t1 ; (e) measuring the output signal for a second sequential instantaneous period of time t2 ; (f) measuring the output signal for a third sequential instantaneous period of time t3 ; (g) subtracting the output signal at t2 from the output signal at t1 which gives a change of signal value CS1 ; (h) subtracting the output signal at t3 from the output signal at t2 which gives a change of signal value CS2 ; (i) subtracting the value CS2 from the value CS1 which gives the change of the change of the signal value CCS1 ; (j) repeating the method steps of (d) through (i) to develop a plurality of CCS data which generates a pattern; and (k) comparing the CCS data of step (j) to corresponding CCS data for the known type of gas at a range of known concentrations and at a range of known temperatures to determine the concentration of the known type gas in the sample mixture contained in the chamber. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for determining the concentration of a known type of gas present in a gas sample mixture comprising:
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(a) a gas chamber having an inlet and an outlet; (b) an infrared light source connectable to a power supply and mounted within the gas chambers; (c) a detector positioned in the gas chamber for detecting the light in the chamber and converting the light detected to an electric output signal which is a function of the light detected; (d) an optical band pass filter also positioned within the chamber; (e) a signal converter connectable to the detector which transforms the electrical output signal from analog output to digital output; and (f) a data acquisition and microprocessor means connected to the signal converter, the data acquisition and microprocessor means having the following functions; (i) measuring the output signal for four sequential instantaneous periods of time t1, t2, t3, t4 ; (ii) determining the relative difference between the output signals at t1 and the output signal at t2 which gives a change of output signal value CS1 ; (iii) determining the relative difference between the output signal at t3 and the output signal at t4 which gives a change of output signal value CS2 ; (iv) determining the relative difference between the change of output signal value CS1 and the change of output signal value CS2 which gives a change of the change of the output signal value CCS1 ; (v) repeating the functions of (i) through (iv) to develop a plurality of CCS data which generates a pattern; and (vi) comparing the CCS data of function (v) to corresponding CCS data for the known type of gas at a range of known concentrations and at a range of known temperatures to determine the concentration of the known type gas in the sample mixture contained in the chamber. - View Dependent Claims (15, 16)
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Specification