Gas sensor with temp. regulation circuit including resistance bridge - has control circuit for maintaining temp. of sensors in resistance bridge circuit constant, with circuit output indicating heat caused by gas

摘要

At the surface of the resistive sensing element (24), the reactive gas produces a specific emission of heat to unbalance the bridge circuit (23-27) which maintains the operating temp. of the sensing element. A feedback operational amplifier (27) in a diagonal of the bridge produces an output which gives a measure of the heat evolved by the gas reaction. A clock-controlled potentiometer (22) is connected to the adjustable resistance (23) and clocked with a periodicity longer than the thermal time constant of the sensor. USE/ADVANTAGE - For detection of trace gases in mixt. analysis. S simple circuit, high sensitivity with very low thermal capacity and time constant.