| 摘要 |
<p>A gas detection sensor system including active and reference elements (Rsense, Rref) are arranged in a modified bridge circuit (12, 14, 22, 24) which allows power (Vbat) to be supplied separately to the active and reference elements (Rsense, Rref). A digital processor (30) monitors the resistances of the elements (Resense, Rref) to control a pulse-width modulator supplying power to the elements, thereby maintaining nearly constant temperatures in the sensor elements (Rsense, Rref), and to translate the decrease in power needed to maintain constant temperature on the catalytic element into an output proportional to the concentration of combustible gas in air. The system periodically measures the resistance of the elements (Rref, Rsense) and is able to dual operating modes of catalytic-bead detector. One active or reference element (Rsense, Rref) can alternately measure low concentrations of combustible gases up to the lower explosive limit (LEL) or measure high concentrations, up to 100% by volume.</p> |
