Abstract: The invention relates to an apparatus for the determination of a concentration of a component to be measured in a gas, comprising a light source, a wavelength selection unit, a measurement cuvette, a reference cuvette arranged in the optical beam path in parallel thereto, at least one light receiver and an evaluation unit which determines the concentration from the signals of the light receiver, wherein the gas to be analyzed is supplied to the measurement cuvette, on the one hand, and, on the other hand, to the reference cuvette via an absorption apparatus which includes a substance which completely absorbs the component to be measured. Further, the component to be measured is H2S and a wavelength selection unit is provided for the selection of an absorption wavelength.

Abstract: A method for measuring NOx having a specific discharge lamp. The method controls a photometric analysis device, in which an electrically rotatable filter wheel or shutter wheel is used to change various shutters and/or filters in a beam path with beam source, cuvette and detector. The filter and/or shutter wheel is controlled in such a way that the measurement time is greater than the transfer time. This control improves the detection limit of the NOx resonance absorption method.

Abstract: An interferometric analyzer for the detection of substances having a structured absorption spectrum such as a periodic or quasiperiodic absorption line pattern, within a gas blend, and comprising a source of radiation for directing radiation into a radiation path that includes a container, cell or the like which contains the substances to be detected, the path includes further a filter system, which includes an electrically or temperature controlled Fabry Perot element such that the spacing between the transmission lines of the interference corresponds to spacing of absorption lines of different substances for different absorption bands of these substances; and a dispersion filter each circularly variable or another Fabry Perot filter is positioned in the radiation path for selecting a respective spectral region as far as a particular substance is concerned by means of the controlled disperging element.

Abstract: An interferometric device for the detection of substances having a periodic or quasiperiodic absorption structure of their absorption spectrum includes a source of radiation, a chamber containing the material to be investigated and a downstream detector, a thermo-optically effective and temperature controlled interference filter means is interposed, its thickness determines the spacing of interference transmission lines and temperature control shifts these lines.

Abstract: Interferometric equipment for detecting a substance having a structure preferably a periodic or quasiperiodic absorption spectrum; the equipment includes a source of radiation, a path for that radiation that includes a sample cell with the substance to be detected, an interference filter and a detector, and is improved in that the interference filter is constructed as an electrically tunable filter, including a plate or cell element with semitransparent reflective boundaries serving as electrodes; an electrical voltage is applied to said electrodes such that the transmission characteristics of the filter is varied and the amplitude of the voltage as applied to these electrodes is an indication of that variation; and the thickness of the plate or cell is selected to meet one of the following criteria (i) a distance between the interference lines produced equals a distance of absorption lines within a periodic absorption spectrum of said substance; (ii) the equipment causes a line to be separated from the radia