SELF-CHECKING FLAME FAILURE CONTROLS

摘要

A self-checking system for monitoring the flame of a burner is disclosed. Radiation from the flame impinges upon two photodetectors which produce two separate but comparable signals. These two signals are applied to a comparator which produces a comparison output which is then used to interpret the signal from one of the sensors so that the comparison output is removed. On removal of the comparison output signal, if the flame is still present, both sensors will once again provide the comparable signals. Thus the circuit provides a modulated signal representing alternately affirmative comparison and negation of comparison. Loss of burner flame or failure or malfunction of any of the circuit components will remove the modulated signal resulting in a failsafe alarm being instigated.