Optopairs with temperature compensable electroluminescence for use in optical gas absorption analyzers

An improved optical absorption gas analyser for determining the concentration of a target gas in a sample, in which is found a chamber for containing the sample in use;

• a radiation source assembly arranged to emit radiation into the chamber;
• a first radiation detector assembly arranged to detect radiation transmitted along a first optical path through the chamber;
• a second radiation detector assembly arranged to detect radiation transmitted along a second optical path through the chamber, wherein the length of the second optical path which the sample can intercept is shorter than that of the first optical path;
• and a processor adapted to generate a sensing signal Sx based on the detected radiation transmitted along the first optical path and a reference signal SR based on the detected radiation transmitted along the second optical path, and to determine the concentration of the target gas in the sample based on a comparison of the sensing signal with the reference signal, wherein the improvement comprises an LED acting as said radiation source assembly arranged to emit radiation into the chamber, said LED having at least one active area whose spectral maximum is de-tuned from the maximum absorption spectrum line of the absorption spectral. band of the gas being analyzed.