Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere

Electrical circuitry for detecting a combustible mixture of gas in a mine atmosphere comprising,

• sensor means for continuously monitoring the level of combustible gas in the mine atmosphere,
• said sensor means operable to supply output signals proportional to the concentration of the combustible mixture of gas in the mine atmosphere,
• power means for actuating said sensor means,
• regulator means for maintaining a preselected input signal to said sensor means,
• said regulator means having detector means for comparing the output signals of said sensor means with a preselected signal and generating an input signal proportional to said output signals from said sensor means,
• an alarm device for actuating a preselected alarm signal to indicate the presence of a combustible mixture of gas in the mine atmosphere, said alarm device arranged to receive an output signal from said regulator detector means for actuating the alarm signal when the output signals of said sensor means exceed a preselected value indicating the presence of a combustible mixture of gas in the mine atmosphere,
• comparator means connected to said regulator means and said power means,
• said comparator means operable to receive said input signals proportional to said sensor means output signals from said regulator means and to generate a corresponding output signal responsive to the maximum input signal received,
• meter means connected to said power means and said comparator means for recording the maximum value of the input signals received by said comparator means from said regulator means, and
• signal deviation detector means for receiving input signals from said regulator means and operable to actuate said alarm device and thereby indicate an excess deviation between the output signals of said sensor means.