Use of Room Temperature Infrared Diodes for Determining Methane Concentration in Air.
Gerritsen-H; Crisman-E; Taylor-CD; Et Al
NTIS: PB/262-649 Available for Reference At Bureau Libraries :96 pages
A device for detecting methane at levels above 0.1 pct in the air is described. It is based on the measurement of infrared absorption at 3.3 Micrometers by methane. The infrared light source is an in.97Ga.03As pn junction and the detector is an inas photovoltaic cell. The optical system was a three-mirror, folded-path cell. Various temperature compensation methods in the 0 to 5 deg c range were investigated. The primary temperature sensitivity is in the inas detector rather than in the emitters. The best system, which was demonstrated in a breadboard device, consisted of two emitters and one detector, one emitter being of a composition or distance from the detector so that it responded very little to methane while the other responded strongly to methane. The ratio then gives the desired methane concentration. Interference with water vapor was negligible and the device draws little power.
CP; Final Contract Report;
NTIS Accession No.
NTIS: PB/262-649 Available for Reference At Bureau Libraries