Development of a continuous methane monitor

Two prototype continuous methane monitors capable of being mounted on a mining machine were designed and built for in mine safety use. The monitors incorporated a nondispersive infrared optical electronic analyzer design in which the response to the sample gas was achieved by synchronous detection and measurement of the amplitude oscillations of the transmitted energy from an infrared source caused by the pressure modulation of the sample gas within the optical cell. Zero and span stability were to be achieved by the amplitude modulating of the infrared source and using the detected signal to correct for optical electronic system variation. This design effort was to simplify and reduce the cost of the major components while eliminating the need for daily calibration.