A. The amount of absorption is related to the concentration of the gas and is measured by a set of optical detectors and suitable electronic systems. B. The change in the intensity of the absorbed light is measured relative to the intensity of light at a non-absorbed wavelength. C. When there is no gas present the signals of reference signal detector and measurement signal detector are balanced. D. When there is combustible gas present, there is a predictable drop in the output from measurement signal detector because the gas is absorbing light. « Previous Next »
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