GB1419361A - Multi-channel combustible gas detector - Google Patents

Abstract

1419361 Measuring gas concentration electrically GENERAL MONITORS Inc 26 March 1974 13358/74 Heading G1N A system for measuring the concentration of a combustible gas in an atmosphere has two parallel sensor circuits feeding into a comparator which provides an indication of the higher concentration, the system including means for indicating malfunction. As shown, Fig.2, two catalytic type resistance sensors 16, 18 are connected in individual bridge networks fed from separate current sources 12, 14. The outputs from the bridges are compared at 52 and the larger signal causes operation of switch 58 or 60 to by-pass the smaller signal and selectively energize the appropriate indicator lamp 80 or 82. The larger signal is further amplified at 84 and fed to a threshold detector 92 associated with alarm devices 108, 118 for a low or high level of gas concentration. The currents fed to the sensor networks are noted at 130, 132 which send corresponding signals to AND gate 134. If one or both currents are missing, an alarm relay 138 is energized. In an alternative arrangement, Fig. 4 (not shown), the output signals from the sensor bridges are fed to a common point through diodes, whereby the largest signal back biases the diodes in the other channels. (For Figure see next page)