Abstract: Apparatus for detecting a combustible gas which comprises a Wheatstone bridge circuit having a detector element comprising an electrically conducting member coated with a refractory and having on the surface of said refractory a catalyst for the oxidation of said gas, said detector element constituting one leg of said bridge, and a reference element comprising an electrically conducting member coated with a refractory, said reference element constituting a second leg of said bridge, whereby upon catalytic oxidation of said gas an electrical signal approximately proportional to the amount of said gas present at the detector element is produced. The improvement comprises a reaction control block having a cover in the form of a dust shield and having two chambers, one containing said detector element, and the other containing said reference element.

Abstract: An improvement is provided in a portable gas detector used to detect combustible gases, such as methane, which embodies a Wheatstone bridge circuit including a refractory-coated detector element having thereon a catalyst for promoting oxidation of the combustible gas to be detected constituting one leg of the bridge and a refractory-coated reference element constituting a second leg of the bridge. The improvement consists in the application of a cobalt oxide coating to the reference element, whereby the occurrence of spurious signals by the Wheatstone bridge circuit due to causes other than the presence of a combustible gas is greatly reduced, if not completely eliminated.

Abstract: An improvement is provided in a portable gas detector used to detect combustible gases, such as methane, which embodies a Wheatstone bridge circuit including a refractory-coated detector element having thereon a catalyst for promoting oxidation of the combustible gas to be detected constituting one leg of the bridge and a refractory-coated reference element constituting a second leg of the bridge. The improvement consists in the application of a cobalt oxide coating to the reference element, whereby the occurrence of spurious signals by the Wheatstone bridge circuit due to causes other than the presence of a combustible gas is greatly reduced, if not completely eliminated.

Abstract: An improvement is provided in apparatus used to detect combustible gases, which embodies a Wheatstone bridge circuit including a refractory-coated detector element having thereon a catalyst for promoting oxidation of the combustible gas to be detected constituting one leg of the bridge and a refractory-coated reference element constituting a second leg of the bridge. The improvement, in its broadest aspect, consists in using a mixture of palladium, palladium oxide and nickel oxide as the catalyst on the detector element. In addition, an improved reference element is provided which has a coating of either sodium metasilicate or lead borate deposited thereon.

Abstract: This is an improvement in apparatus for detecting combustible gases, such as methane, that embodies a Wheatstone bridge circuit including a refractory-coated reference element constituting one leg of the bridge and a refractory-coated detector element having thereon a catalyst for promoting oxidation of the combustible gas to be detected constituting a second leg of the bridge. Upon oxidation of combustible gas at the detector element the temperature and resistance thereof increases relative to the reference element to unbalance the bridge, thereby producing an electrical signal proportional to the amount of combustible gas being oxidized. This invention improves the stability, linearity, and stabilization time of the bridge signal by constructing the reference element so that at zero percent combustible gas or during oxidation of the combustible gas at the detector element the radiant energy of both the detector and reference element are substantially equal.