Device for determining the nitrogen oxide concentration in a gaseous mixture

摘要

Apparatus for determining the nitrogen oxide concentration in a gaseous mixture while minimizing measuring errors. The radiation from a hollow cathode lamp emitting the nitrogen oxide resonance radiation is modulated by a device for generating alternatively an unfiltered or test beam and a reference beam. The reference beam is filtered by a nitrogen oxide filled filter. An absorption cell is disposed in the path of the reference beam. Further, a monochromator or filter is provided and a detector for receiving the radiation from the monochromator filter. A signal processing unit is coupled to the detector for forming electric signals corresponding to the signal from the unfiltered and the reference beam and for forming the quotient thereof. A ray splitter is disposed in the path of the two beams to provide a different beam path and an additional radiation detector is disposed in the additional path. The signal processing unit has additional means for forming the quotient of the two signals generated by the additional detector and which have not passed the absorption cell. This will then provide an additional quotient of the two available quotients thus minimizing the normally occurring errors.