Remote controller for detection of combustible gas - employs multivibrator to apply pulses to power measuring bridge circuits in explosion proof housing

摘要

A Wheatstone bridge (1) contains a compensating filament (2) and detector filament (3) for a catalytic gas detector. A potentiometer (6) provides bridge balancing. An amplifier (7) is connected diagonally across the bridge while a second amplifier (19) is connected across a second bridge circuit (13). The amplifier outputs are connected to a sampling circuit (23) whose output drives a galvanometer (26) via an RC (24,25) circuit. A bistable circuit (12) compares the sampled value with a reference value and enables respective gates (10,21). This allows a multivibrator (11) to apply pulses via transistors (9,20) in the bridge circuits and thereby power the bridges.