Determination of the partial pressure and the concentration of a gas
First Claim
1. In a method for determining the partial pressure and concentration of a measuring gas which is in mixture with at least one additional gas according to an optical absorption technique, which method includes producing a beam of light having a predetermined intensity, filtering the beam to alternatingly and cyclically give the light a first spectral distribution in which the light intensity will be reduced by passage through the measuring gas and a second spectral distribution in which the light intensity will not be reduced by passage through the measuring gas, passing the filtered beam through such a mixture, measuring the radiation intensity of the beam after passage through the mixture in a radiation detector having an active element which is heated by the radiation and which produces an output representative of its degree of heating, the output being composed of successive measuring signal segments, resulting from light having the first spectral distribution, alternating with successive reference signal segments, resulting from light having the second spectral distribution, and processing adjacent measuring signal and reference signal segments in order to compensate for fluctuations in the light beam being produced, variations in the light transmission and reflection properties of the beam path and other interference effects, the improvement wherein said step of processing comprises supplying the detector output to an input amplifier having a large signal to noise ratio, and compensating for signal inaccuracies due to superimposition of each signal segment portion produced by heating of the active element on a component representing the cooling behavior which the element would experience after the preceding heating period if further heating did not occur, said compensating step being performed by:
- integrating, in an integration member, each measuring signal occurring during a period when the element is being heated by the radiation, which integration is performed with respect to an integration base;
applying to the integration member a direct voltage whose value determines the integration base; and
adjusting the direct voltage to a magnitude which will cause the integral of a measuring signal, with respect to the integrator base, to have a value of zero when light having the first spectral distribution experiences maximum intensity reduction upon passage through such measuring gas.
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Abstract
For determining the partial pressure and concentration of a measuring gas which is in mixture with at least one additional gas according to an optical absorption technique, in which a beam of light having a predetermined intensity and alternatingly and cyclically having a first spectral distribution in which the light intensity will be reduced by passage through the measuring gas and a second spectral distribution in which the light intensity will not be reduced by passage through the measuring gas, is passed through such a mixture and its radiation intensity after passage through the mixture is measured in a radiation detector having an active element which is heated by the radiation and which produces an output representative of its degree of heating and composed of alternating measuring signal segments, resulting, respectively, from light having the first and the second spectral distribution, and adjacent signals segments are processed in order to compensate for various interference effects, the detector output is delivered to an input amplifier having a large signal to noise ratio, and signal inaccuracies due to superimposition of each signal segment portion produced by heating of the active element on a component representing the cooling behavior which the element would experience after the preceding heating period if further heating did not occur are compensated by integrating, in an integration member, successive portions of the detector output with respect to an integration base which has a fixed value relative to the detector output value corresponding to a constant active element temperature.
28 Citations
19 Claims
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1. In a method for determining the partial pressure and concentration of a measuring gas which is in mixture with at least one additional gas according to an optical absorption technique, which method includes producing a beam of light having a predetermined intensity, filtering the beam to alternatingly and cyclically give the light a first spectral distribution in which the light intensity will be reduced by passage through the measuring gas and a second spectral distribution in which the light intensity will not be reduced by passage through the measuring gas, passing the filtered beam through such a mixture, measuring the radiation intensity of the beam after passage through the mixture in a radiation detector having an active element which is heated by the radiation and which produces an output representative of its degree of heating, the output being composed of successive measuring signal segments, resulting from light having the first spectral distribution, alternating with successive reference signal segments, resulting from light having the second spectral distribution, and processing adjacent measuring signal and reference signal segments in order to compensate for fluctuations in the light beam being produced, variations in the light transmission and reflection properties of the beam path and other interference effects, the improvement wherein said step of processing comprises supplying the detector output to an input amplifier having a large signal to noise ratio, and compensating for signal inaccuracies due to superimposition of each signal segment portion produced by heating of the active element on a component representing the cooling behavior which the element would experience after the preceding heating period if further heating did not occur, said compensating step being performed by:
- integrating, in an integration member, each measuring signal occurring during a period when the element is being heated by the radiation, which integration is performed with respect to an integration base;
applying to the integration member a direct voltage whose value determines the integration base; and
adjusting the direct voltage to a magnitude which will cause the integral of a measuring signal, with respect to the integrator base, to have a value of zero when light having the first spectral distribution experiences maximum intensity reduction upon passage through such measuring gas. - View Dependent Claims (2, 3)
- integrating, in an integration member, each measuring signal occurring during a period when the element is being heated by the radiation, which integration is performed with respect to an integration base;
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4. In a method for determining the partial pressure and concentration of a measuring gas which is in mixture with at least one additional gas according to an optical absorption technique, which method includes producing a beam of light having a predetermined intensity, filtering the beam to alternatingly and cyclically give the light a first spectral distribution in which the light intensity will be reduced by passage through the measuring gas and a second spectral distribution in which the light intensity will not be reduced by passage through the measuring gas, passing the filtered beam through such a mixture, measuring the radiation intensity of the beam after passage through the mixture in a radiation detector having an active element which is heated by the radiation and which produces an output representative of its degree of heating, the output being composed of successive measuring signal segments, resulting from light having the first spectral distribution, alternating with successive reference signal segments, resulting from light having the second spectral distribution, and processing adjacent measuring signal and reference signal segments in order to compensate for fluctuations in the light beam being produced, variations in the light transmission and reflection properties of the beam path and other interference effects, the improvement wherein said step of processing comprises supplying the detector output to an input amplifier having a large signal to noise ratio, and compensating for signal inaccuracies due to superimposition of each signal segment portion produced by heating of the active element on a component representing the cooling behavior which the element would experience after the preceding heating period if further heating did not occur, said compensating step being performed by:
- integrating, in an integration member, successive portions of the detector output with respect to an integration base which has a fixed value relative to the detector output value corresponding to a constant active element temperature, with the period of each integration being set by successive passage of the detector output through such values, thereby producing, cyclically and successively, a first integral corresponding in time to heating of the active element during a reference signal segment, a second integral corresponding in time to the respective succeeding cooling of the active element, a third integral corresponding in time to heating of the active element during the succeeding measuring signal segment, and a fourth integral corresponding in time to the respective succeeding cooling of the active element;
determining the actual difference between the first and second integrals;
determining the actual difference between the third and fourth integrals;
determining the difference which would exist between the third and fourth integrals if the measuring gas were present at a very high pressure; and
subtracting the difference which would exist from each of the actual differences. - View Dependent Claims (5, 6, 7, 8)
- integrating, in an integration member, successive portions of the detector output with respect to an integration base which has a fixed value relative to the detector output value corresponding to a constant active element temperature, with the period of each integration being set by successive passage of the detector output through such values, thereby producing, cyclically and successively, a first integral corresponding in time to heating of the active element during a reference signal segment, a second integral corresponding in time to the respective succeeding cooling of the active element, a third integral corresponding in time to heating of the active element during the succeeding measuring signal segment, and a fourth integral corresponding in time to the respective succeeding cooling of the active element;
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9. In apparatus for determining the partial pressure and concentration of a measuring gas which is in mixture with at least one additional gas according to an optical absorption technique, which apparatus includes a light source producing a beam of light having a predetermined intensity, optical filter means arranged to filter the beam to alternatingly and cyclically give the light a first spectral distribution in which the light intensity will be reduced by passage through the measuring gas and a second spectral distribution in which the light intensity will not be reduced by passage through the measuring gas, a sample container arranged to contain such a gas mixture and disposed in the path of the filtered light beam beyond the filter means, a radiation detector disposed to receive the beam after passage through the container and having an active element which is heated by the radiation, the detector producing an output proportional to the degree of heating of the active element, the output being composed of successive measuring signal segments, resulting from light having the first spectral distribution, alternating with successive reference signal segments, resulting from light having the second spectral distribution, and means connected for processing adjacent measuring signal and reference signal segments in order to compensate for fluctuations in the light beam being produced, variations in the light transmission and reflection properties of the beam path and other interference effects, the improvement wherein said signal processing means are arranged for compensating for signal inaccuracies due to superimposition of each signal segment portion produced by heating of the active element on a component representing the cooling behavior which the element would experience after the preceding heating period if further heating did not occur, and include:
- an analog computer stage containing an input amplifier having a large signal to noise ratio and connected to receive the detector output;
a digital control unit connected for controlling the operation of said computer stage;
a first indicator unit connected to said computer stage for providing an indication of the partial pressure of the measuring gas in said container; and
a second indicator connected to said computer stage for providing an indication of the concentration of the measuring gas in said container. - View Dependent Claims (10, 11, 12, 13, 14)
- an analog computer stage containing an input amplifier having a large signal to noise ratio and connected to receive the detector output;
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15. In apparatus for determining the partial pressure and concentration of a measuring gas which is in mixture with at least one additional gas according to an optical absorption technique, which apparatus includes a light source producing a beam of light having a predetermined intensity, optical filter means arranged to filter the beam to alternatingly and cyclically give the light a first spectral distribution in which the light intensity will be reduced by passage through the measuring gas and a second spectral distribution in which the light intensity will not be reduced by passage through the measuring gas, a sample container arranged to contain such a gas mixture and disposed in the path of the filtered light beam beyond the filter means, a radiation detector disposed to receive the beam after passage through the container and having an active element which is heated by the radiation, the detector producing an output proportional to the degree of heating of the active element, the output being composed of successive measuring signal segments, resulting from light having the first spectral distribution, alternating with successive reference signal segments, resulting from light having the second spectral distribution, and means connected for processing adjacent measuring signal and reference signal segment in order to compensate for fluctuations in the light beam being produced, variations in the light transmission and reflection properties of the beam path and other interference effects, the improvement wherein said signal processing means are arranged for compensating for signal inaccuracies due to superimposition of each signal segment portion produced by heating of the active element on a component representing the cooling behavior which the element would experience after the preceding heating period if further heating did not occur, and include:
- a digital computer stage containing an input amplifier having a large signal to noise ratio and connected to receive the detector output;
a digital control unit connected for controlling the operation of said computer stage;
a first indicator unit connected to said computer stage for providing an indication of the partial pressure of the measuring gas in said container; and
a second indicator connected to said computer stage for providing an indication of the concentration of the measuring gas in said container. - View Dependent Claims (16, 17, 18, 19)
- a digital computer stage containing an input amplifier having a large signal to noise ratio and connected to receive the detector output;
Specification