Patent ID: 8293179

Claim:
A gas detection apparatus comprising: a gas sensing unit having a detection resistor heated by Joule heat in the presence of an electric current flowing therethrough and an igniter configured to ignite a flammable gas by a catalytic action as a result of being heated by the heat of said detection resistor; a load resistor connected in series to said detection resistor; a plurality of bridge resistors connected between both ends of a series circuit composed of said detection resistor and said load resistor to form a bridge circuit with the series circuit; a heater voltage application circuit configured to apply a pulsed heater voltage having a cycle shorter than a thermal time constant of said gas sensing unit across the series circuit composed of said detection resistor and said load resistor; a first integrating circuit unit composed of a CR integrating circuit including a resistor and a capacitor, and configured to integrate a voltage at a connection point between said detection resistor and said load resistor; a second integrating circuit unit composed of a CR integrating circuit including a resistor and a capacitor, and configured to integrate a voltage at a connection point between said bridge resistors; a differential amplification circuit unit configured to amplify a differential voltage between output voltages of both said integrating circuit units; and a gas detection circuit configured to provide an output signal of a magnitude corresponding to a concentration of the flammable gas from an output of said differential amplification circuit unit.