Gas detecting circuit

Claim 1

CIRCUIT ARRANGEMENT FOR DETECTING THE PRESENCE OF SMALL QUANTITIES OF A COMBUSTIBLE GAS PRESENT IN AN ATMOSPHERE COMPRISING IN COMBINATION A GAS DETECTING ELEMENT INCORPORATING A MATERIAL WHICH IN THE PRESENCE OF THE COMBUSTIBLE GAS ACTS AS A CATALYST TO PROMOTE COMBUSTION OF THE COMBUSTIBLE GAS ON THE ELEMENT AND A CONSEQUENTIAL HEATING OF THE ELEMENT, A CLOSED VESSEL OF LOW INTERNAL VOLUME ENCLOSING THE GAS DETECTING ELEMENT AND HAVING AT LEAST A LARGE PART THEREOF MADE OF A POROUS SINTERED METAL THROUGH WHICH THE GASES OF AN ATMOSPHERE SURROUNDING THE VESSEL MAY DIFFUSE INTO THE VESSEL, THE SAID POROUS PART OF THE CLOSED VESSEL HAVING A POROSITY SUCH THAT THE FLOW OF GASES FROM THE SURROUNDING ATMOSPHERE INTO THE VESSEL IS SUBSTANTIALLY IMPEDED AND SUCH THT GASES FROM THE SURROUNDING ATMOSPHERE MAY DIFFUSE INTO THE VESSEL AT A RATE SUFFICIENT TO JUST MAINTAIN COMBUSTION OF THE COMBUSTIBLE GAS ADJACENT THE SURFACE OF THE GAS DETECTING ELEMENT AT A RATE DEPENDENT UPON THE PROPORTION OF THE COMBUSTIBLE GAS PRESENT IN THE ATMOSPHERE SURROUNDING THE VESSEL WITHOUT CAUSING ANY SUBSTANTIAL PRESSURE CHANGE INSIDE THE VESSEL, AND THE INTERNAL VOLUME OF THE VESSEL BEING SUITABLY LOW AS TO REDUCE TO A LOW VALUE THE DISSIPATION OF HEAT FROM THE GAS DETECTING ELEMENT BY CONVECTION, AND MEANS FOR PRODUCING AN ELECTRIC SIGNAL DEPENDENT UPON SAID HEATING CAUSING A CHANGE IN TEMPERATURE OF THE GAS DETECTING ELEMENT BROUGH ABOUT BY SAID COMBUSTION OF THE COMBUSTIBLE GAS IN CONTACT THEREWITH.