Tragbares Messgeraet zur Bestimmung des Gasgehaltes im Wetterstrom unter Tage

1,110,778. Determining the gas content of air, electrically. R. HœBNER. Jan.4, 1966 [Jan.19, 1965], No.219/66. Heading G1N. A portable instrument, for the determination of methane gas content of air, having a measuring chamber, a motor driven pump to draw an air sample into the chamber wherein gas is burnt catalytically, and a measuring circuit (e.g. a bridge) which utilizes change in resistance of a catalytic resistor to provide a measure of the gas content, is characterized by a delay circuit which provides an adjustable delay of at least one second between switching off of the pump motor and energization of the measuring circuit. Thereby inaccurate measurement due to eddies in the air sample are avoided. The operation of the delay circuit is not described in detail. The instrument may be as described in Specification 1,097,641.