A method for spark rejection in ultraviolet flame detectors

A novel method is presented to render ultraviolet (UV) flame detectors inse nsitive to ignition spark radiation. The method involves isolating the sign al due to the sparks from the UV-sensor output and subtracting a de signal proportional to it from the output of the flame detector sensor system. A p ractical demonstration of the method is given using a commercially availabl e UV flame detector with the addition of an analog circuit to perform the n ecessary signal processing. A selectivity improvement to spark radiation of greater than 130 has been obtained. The method is robust in that it is ind ependent of the distance between the light source and the flame detector an d has been designed to work with different spark generators found on the ma rket. The analog circuit is simple, requiring few components, thus ensuring rugged, fail-safe operation and low cost.