Apparatus and method for determining the proportion of a substance in a gas sample using an infrared measuring instrument

摘要

The invention relates to an apparatus and a method for improved correction of drift in an infrared measuring instrument. The measurement signal furnished by a thermal detector is split into a direct voltage component and an alternating voltage component. By means of calibration curves ( 24, 27 ), a calculated comparison variable $T_{\mathrm{DC},\mathrm{korr}}^{900}$ is formed from a measured, averaged concentration value $c_{\mathrm{AC1}}^{900}.$ The correction value DeltaT for the drift correction is obtained from the difference between the corresponding measured size of the direct voltage component $T_{\mathrm{DC}}^{900}$ and the comparison variable $T_{\mathrm{DC},\mathrm{korr}}^{900}.$