Flame monitoring system for combustion system burners - has liquid crystal diaphragm to modulate signal light from burner flame to sensor

摘要

The device is for flame sensing or monitoring in burners employed in a heating or combustion installation. The line of sight connecting the flame and an optical flame sensor is periodically interrupted, has an electronically controlled liquid crystal diaphragm (3) mounted in front of the optical flame sensor (6). The optical signal panes from the flame (2) to the sensor (6) solely through this liquid crystal diaphragm (3). The liquid crystal is periodically altered from its clear to its non-transparent state and the resulting modulated signal is evaluated by a frequency filter (9) after passage from the flame sensor (6) before transmission of a warning or alarm system.