Electrical circuitry for detecting a combustible mixture of gas in a

Abstract

A pair of sensor assemblies that change in electrical resistance when exposed to a mixture of combustible gas are positioned at a selected location in a mine or on a piece of operating equipment and receive power for continuous operation from a regulated power source. Regulator devices maintain a preselected input signal to the sensor assemblies. When exposed to a mixture of combustible gas, the sensor assemblies generate output signals which are received by a comparator and switch assembly. If an output signal of a sensor assembly exceeds a preselected signal of the comparator associated therewith, an alarm signal is generated and an audible and visual alarm device is actuated to indicate the presence of a combustible mixture of gas in the mine atmosphere. A time delay mechanism is operable to interrupt the input signal to the sensor assemblies if the alarm signal continues longer than a preselected interval. The time delay mechanism also generates a latch signal to continue generation of the alarm signal when the presence of combustible gas has been detected. The regulator device for each sensor assembly transmits an amplified signal proportional to the sensor output signal to a signal deviation detector. If the difference between the amplified signals of the sensor assemblies exceed a preselected value, the signal deviation detector also transmits an output signal to the above alarm device and time delay mechanism.