Method for detecting a gas using an infrared gas analyser and gas analyser suitable for carrying out said method

A method for detecting a test gas that may be present at a measuring location, using an infrared gas analyser, said analyser comprising:

• a cuvette accepting the gases to be analysed, an infrared light source located at one face side of the cuvette, an infrared detector located at the other face side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at the measuring location, and two gas lines serving the purpose of supplying gases to the infrared gas analyser in which a first of said gas lines is adapted to take up a measuring gas at said measuring location that may contain test gas and a second of said gas lines is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present, said method including the steps of:
• taking up the measuring gas at the measuring location:
• and
• feeding the reference gas to the cuvette of the infrared gas analyser such that the measuring gas taken up at the measuring location constantly flows through the cuvette;
• and
• adding reference gas to the cuvette periodically and where only in the instance that at the measuring location test gas is taken up, the concentration of which is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration.

An infrared gas analyzer for detecting a test gas that may be present at a measuring location said analyzer comprising:

• a cuvette accepting the gases to be analyzed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at an opposite side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at the measurement location;
• and
• first and second gas lines serving the purpose of supplying gases to the infrared gas analyser wherein the first gas line is adapted to take up a measuring gas at a measuring location that may contain test gas and where the second gas line is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present wherein said device further includes means for admitting measuring gas taken up at the measuring location and the reference gas into the cuvette of an infrared gas analyser in such a manner that they are alternately present in the cuvette and in which said analyzer provides alternating signals indicative of an increased test gas concentration at the measuring location only when the measuring location test gas concentration is higher than the test gas concentration of said reference gas.

An infrared gas analyzer for detecting a test gas that may be present at a measuring location, said analyzer comprising:

• a cuvette accepting the gases to be analysed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at the other face side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at the measuring location;
• and
• two gas lines serving the purpose of supplying gases to the infrared gas analyser in which a first of said gas lines is adapted to take up a measuring gas at a measuring location that may contain test gas and a second of said gas lines is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present, wherein the measuring gas is taken up at the measuring location and the reference gas is fed to the cuvette such that the measurement gas taken up at the measuring location constantly flows through the cuvette, and gas admitting means for adding reference gas at times wherein said analyzer provides alternating signals indicative of an increased test gas concentration only when the measuring location test gas concentration is higher than the test gas concentration of the reference gas, said gas admitting means including a control valve in the second gas line serving the purpose of supplying the reference gas.

An infrared gas analyzer for detecting a test gas that may be present at a measuring location, said analyzer comprising:

• a cuvette accepting the gases to be analyzed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at an opposite side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at the measuring location;
• two gas lines serving the purpose of supplying gases to the infrared gas analyser wherein a first of said gas lines is adapted to take up a measuring gas at a measuring location that may contain test gas and where a second gas line is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present;
• and
• gas admitting means for admitting measuring gas taken up at the measuring location and the reference gas into the cuvette such that the reference gas and measuring gas are alternately present, and only in the instance that at the measuring location test gas is taken up, the concentration of which in the measuring gas is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration, wherein for signal processing lock-in technology is employed including at least one lock-in amplifier as a component of the electronics, and a line carrying a clock signal from said amplifier being connected to at least one of said gas admitting means and said infrared light source.

An infrared analyzer for detecting a test gas that may be present at a measuring location, said analyzer comprising:

• a cuvette accepting the gases to be analyzed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at an opposite side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at the measuring location;
• two gas lines serving the purpose of supplying gases to the infrared gas analyser wherein a first of said gas lines is adapted to take up a measuring gas at a measuring location that may contain test gas and where a second gas line is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present, and in which measuring gas is taken up at the measuring location and reference gas is fed to the cuvette such that the reference gas and measuring gas are alternately present;
• gas admitting means for admitting measuring gas taken up at the measuring location and the reference gas into the cuvette such that the reference gas and measuring gas are alternately present, and only in the instance that at the measuring location test gas is taken up, the concentration of which in the measuring gas is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration;
• and
• means for constantly monitoring the operation of the gas analyzer including means for exchanging the measuring gas and the reference gas at a fundamental frequency fg and means for modulating the infrared light source with a reference frequency fr including a second lock-in amplifier, the line carrying the clock signal for the reference frequency being connected to the infrared light source.

An infrared gas analyzer for detecting a test gas that may be present at a measuring location, said analyzer comprising:

• a cuvette accepting the gases to be analyzed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at an opposite side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at a measuring location;
• two gas lines serving the purpose of supplying gases to the infrared gas analyser wherein a first of said gas lines is adapted to take up a measuring gas at the measuring location that may contain test gas and where a second gas line is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present;
• and
• gas admitting means for admitting measuring gas taken up at the measuring location and the reference gas into the cuvette such that the reference gas and measuring gas are alternately present, and only in the instance that at the measuring location test gas is taken up the concentration of which in the measuring gas is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration, wherein said gas flow is being continuously monitored by said device including a differential pressure sensor connected to each of the first and second gas lines wherein the output of the pressure sensor is connected to processing logic.

An infrared gas analyser comprising:

• a cuvette accepting gases to be analysed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at the other face side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at a measuring location;
• two gas lines serving the purpose of supplying gases to the infrared gas analyser in which a first of said gas lines is adapted to take up a measuring gas at a measuring location that may contain test gas and a second of said gas lines is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present;
• means for taking up the measuring gas at the measuring location;
• means for admitting the reference gas to the cuvette such that the measuring gas taken up at the measuring location constantly flows through the cuvette wherein reference gas is added at times and only in the instance that at the measurement location test gas is taken up, the concentration of which is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration wherein for signal processing, a first lock-in amplifier processes the alternating signals to the detector;
• said analyzer further including a line carrying a clock signal from said first lock-in amplifier connecting at least one of the gas admitting means to said cuvette and to said infrared light source.

An infrared gas analyzer for detecting a test gas that may be present at a measuring location, said analyzer comprising:

• a cuvette accepting gases to be analyzed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at the other face side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at measuring location;
• two gas lines serving the purpose of supplying gases to the infrared gas analyser in which a first of said gas lines is adapted to take up a measuring gas at the measuring location that may contain test gas and a second of said gas lines is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present;
• means for taking up the measuring gas at the measuring location;
• and
• means for admitting the reference gas to the cuvette such that the measuring gas taken up at the measuring location constantly flows through the cuvette wherein reference gas is added at times and only in the instance that at the measurement location test gas is taken up, the concentration of which is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration;
• and
• means for constantly monitoring the operation of the gas analyzer including means for exchanging gas at a fundamental frequency fg and modulating the infrared light source with a reference frequency fr, and further including a lock-in amplifier connected by a line to the infrared light source for carrying a clock signal for the reference frequency fr.

An infrared gas analyzer for detecting a test gas that may be present at a measuring location, said analyzer comprising:

• a cuvette accepting the gases to be analyzed;
• an infrared light source located at one face side of the cuvette;
• an infrared detector located at an opposite side of the cuvette, the signals from the infrared detector serving the purpose of determining test gas recorded at a measuring location;
• two gas lines serving the purpose of supplying gases to the infrared gas analyser wherein a first of said gas lines is adapted to take up a measuring gas at a measuring location that may contain test gas and where a second gas line is adapted to take up gas from the surroundings of the measuring location (reference gas), which gas may contain a test gas background that is to be taken into consideration when detecting the test gas taken up at the measuring location, wherein only one cuvette is present;
• means for taking up the measuring gas at the measuring location;
• means for admitting the reference gas to the cuvette such that the measuring gas taken up at the measuring location constantly flows through the cuvette wherein reference gas is added at times and only in the instance that at the measurement location test gas is taken up, the concentration of which is higher than the test gas concentration in the reference gas, do the alternating signals supplied by the infrared detector serve the purpose of determining the increased test gas concentration;
• and
• wherein said gas flow is being continuously monitored, said device including a differential pressure sensor connected to each of the first and second gas lines wherein the output of the differential pressure sensor is connected to processing logic.