Method of compensating for carrier-gas-composition dependence due to the collision-broadening effect in non-dispersive infrared photometers having a detector comprised of two absorption chambers arranged one behind the other

Claim 1

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing an infrared-active gas component whose concentration is to be measured accompanied by a carrier gas, the carrier gas comprising at least one component which is infrared-inactive, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette.

Claim 2

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing an infrared-active gas component whose concentration is to be measured accompanied by a carrier gas, the carrier gas comprising at least one component which is infrared-inactive, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette.

Claim 3

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the adjusting step comprising adjusting only the absorption chambers of the detector.

Claim 4

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the adjusting step comprising adjusting only the absorption chambers of the detector.

Claim 5

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the adjusting step comprising adjusting the optical path-lengths of the absorption chambers.

Claim 6

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the adjusting step comprising adjusting the optical path-lengths of the absorption chambers.

Claim 10

A method of setting up a non-dispersive infrared photometer of the type comprised of a light souce, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the adjusting step comprising adjusting the photometer to render the measurement signal independent of the carrier-gas composition to below the resolution limit.

Claim 11

A method of setting up a non-dispersive infrared photometer of the type comprised of a light souce, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the adjusting step comprising adjusting the photometer to render the measurement signal independent of the carrier-gas composition to below the resolution limit.

Claim 12

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the carrier gas consisting predominantly of a first gas component in a second gas component, the adjusting step comprising adjusting the photometer to render the measurement signal independent of the carrier-gas composition to below the resolution limit for the entire range of 0 - 100% of the first gas component in the second gas component.

Claim 13

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the carrier gas consisting predominantly of a first gas component in a second gas component, the adjusting step comprising adjusting the photometer to render the measurement signal independent of the carrier-gas composition to below the resolution limit for the entire range of 0 - 100% of the first gas component in the second gas component.

Claim 14

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the carrier gas consisting of a plurality of gas components, the absorption chambers each containing a gas identical to the gas whose concentration is to be measured accompanied by an inert gas, the adjusting step comprising obtaining a plurality of test gas samples, each test gas sample having the same concentration of the gas component whose concentration is to be measured, but different relative proportions of the components of the carrier gas, successively introducing each of the test gas samples into the measurement cuvette and performing a photometric measurement of the concentration of the gas component whose concentration is to be measured, determining the dependence of the measurement signal upon the differences in the relative proportions of the components of the carrier gas, based upon that determination changing the concentration in the absorption chambers of the gas identical to the gas whose concentration is to be measured, again performing photometric gas concentration measurements using the test gas samples, again determining the dependence of the detector output signal upon the carrier-gas composition, based upon the last-mentioned determination again changing the concentration of the gas in the absorption chamber, and repeating these steps until the output signal of the detector is made substantially independent of carrier-gas composition changes.

Claim 15

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the carrier gas consisting of a plurality of gas components, the absorption chambers each containing a gas identical to the gas whose concentration is to be measured accompanied by an inert gas, the adjusting step comprising obtaining a plurality of test gas samples, each test gas sample having the same concentration of the gas component whose concentration is to be measured, but different relative proportions of the components of the carrier gas, successively introducing each of the test gas samples into the measurement cuvette and performing a photometric measurement of the concentration of the gas component whose concentration is to be measured, determining the dependence of the measurement signal upon the differences in the relative proportions of the components of the carrier gas, based upon that determination changing the concentration in the absorption chambers of the gas identical to the gas whose concentration is to be measured, again performing photometric gas concentration measurements using the test gas samples, again determining the dependence of the detector output signal upon the carrier-gas composition, based upon the last-mentioned determination again changing the concentration of the gas in the absorption chamber, and repeating these steps until the output signal of the detector is made substantially independent of carrier-gas composition changes.

Claim 16

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the carrier gas in the measurement cuvette consisting of a plurality of carrier-gas components, the adjusting step comprising adjusting the photometer to render the measurement signal substantially independent of the relative proportions of the carrier-gas components.

Claim 17

A method of setting up a non-dispersive infrared photometer of the type comprised of a light source, a reference cuvette containing a reference gas, a measurement cuvette containing a gas component whose concentration is to be measured accompanied by a carrier gas, a light modulator for effecting antiphase modulation of the light passing through the two cuvettes, and a detector arrangement comprised of two gas-filled absorption chambers arranged one behind the other and a transducer for converting pressure changes induced in the absorption chambers into a measurement signal, the method comprising the step of adjusting the photometer to render the measurement signal substantially independent of the composition of the carrier gas in the measurement cuvette, the carrier gas in the measurement cuvette consisting of a plurality of carrier-gas components, the adjusting step comprising adjusting the photometer to render the measurement signal substantially independent of the relative proportions of the carrier-gas components.