Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Patent
1987-06-04
1989-05-30
LaRoche, Eugene R.
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
356437, 356438, G01J 142, G01N 2100
Patent
active
048353930
ABSTRACT:
To improve the accuracy and reduce the sensitivity of interference absorptions in a method for determining the concentration of formaldehyde in a medium by an absorption measurement in the range of at least one characteristic absorption band of the formaldehyde and, in the appropriate instance, subtraction of an interference absorption which is determined by at least one absorption measurement in a wavelength range outside of the characteristic absorption band of the formaldehyde, it is proposed that a discharge be maintained at a current strength of several milliamperes in a hollow-cathode lamp filled with molecular nitrogen at a pressure of less than 2 millibar to generate the radiation for the absorption measurement, that the absorption measurement be performed on at least two different characteristic absorption bands of the formaldehyde with absorption coefficients at a previously known ratio to one another which lie in the range of emissions of the gas discharge in the hollow-cathode lamp, that the ratio of the actual absorptions measured on the characteristic absorption bands be formed and compared with the previously known ratio, that in the event of non-coincidence with the previously known ratio, the interference absorption be determined and subtracted from the measured absorptions, and that in the event of coincidence with the previously known ratio, the concentration of the formaldehyde be determined from the measured absorption values or, if interference absorptions are to be subtracted, from the absorption values which have been reduced by the interference absorption.
REFERENCES:
patent: 4536090 (1985-08-01), Schmidt et al.
Analytical Chemistry, "Generation of Formaldehyde in Test Atmospheres with ow Concentrations of Hydrogen and Carbon Monoxide", 1983, pp. 1440-1442.
Technisches Messen, Band 50, No. 11, Nov. 1983, pp. 417-422.
Deutsche Forschungs -und Versuchsanstalt fur Luft -und Raumfahrt
LaRoche Eugene R.
Mis David
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