Method and arrangement for determining nitric oxide concentration
AssigneeDeutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt e.V.
InventorHelmut Meinel
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Abstract
A method and arrangement for determining the concentration of nitric oxide n a gas mixture, particularly exhaust gases, wherein a beam from a hollow-cathode tube is directed through a modulator, an absorption cell containing a gas mixture with an unknown concentration of nitric oxide, and a monochromator, to a beam detector. A readout arrangement displaying the concentration of nitric oxide gas is operatively connected to the beam detector.
Claims42
A method of determining the concentration of nitric oxide (NO) in a gas mixture of unknown composition, particularly exhaust gas, comprising the steps of pumping air through a hollow-cathode tube and keeping the air pressure therein subatmospheric;
- continuously producing in the tube, from the nitrogen and oxegen in the air passing therethrough, excited nitric oxide molecules which emit radiation consisting of a plurality of discrete rotational spectral lines, by applying a potential difference across the anode and cathode of the tube and operating the tube at a current having an order of magnitude of about 1 milliampere;
- directing a beam of such radiation through said gas mixture so that such radiation becomes attentuated due to resonance absorption by nitric oxide molecules in said gas mixture;
- and measuring said attentuation.
An arrangement for measuring the concentration of nitric oxide (NO) in a gas mixture of unknown composition, comprising, in combination, a hollow-cathode tube comprised of a container having an inlet and an outlet and an anode and a can-like cathode in the container;
- pump means for pumpting air through said tube;
- valve means connected to said inlet operative for keeping the air pressure in said tube subatmospheric;
- means for effecting continuous conversion of nitrogen and oxygen in the air passing through said tube into excited nitric oxide molecules which emit to outside said tube radiation consisting of a plurality of discrete rotational spectral lines;
- a radiation detector located in the path of the radiation emitted from said tube by said excited nitric oxide molecules;
- and in the path of said radiation intermediate said tube and said detector an absorption cell for holding said gas mixture.
A method of determining the concentration of nitric oxide (NO) in a gas mixture of unknown composition, particularly exhaust gas, comprising the steps of generating radiation consisting of a plurality of discrete rotational spectral lines emitted from excited nitric oxide molecules;
- directing a beam of such radiation through said gas mixture so that such radiation becomes attenuated due to absorption by nitric oxide molecules in said gas mixture;
- and measuring the attenuation.
An arrangement for measuring the concentration of nitric oxide (NO) in a gas mixture of unknown composition, comprising, in combination, means for generating radiation consisting of a plurality of discrete rotational spectral lines emitted from excited nitric oxide molecules;
- means for directing a beam of such radiation through said gas mixture so that such radiation becomes attenuated due to absorption by nitric oxide molecules in said gas mixture;
- and means for measuring said attenuation.
Dependencies are inferred from the claim text.