Flame thermal radiation has the discrete spectrum of gas radiation and continuous spectrum of solid radiation YS 17 flame using infrared sensor on the characteristics of the flame is very sensitive use special infraredreceiving tube to detect flame thermal radiation and then the flame brightness changes into high and low levelsignal again through the comparator compared with reference voltage threshold reachesthe threshold voltage output low level modules.YS 17 flame sensor for all kinds of fire fire detection.Can detect the flame or wavelength at 760 nm to 1100 nm range of light source the greater the flame test the farther the distance detection Angle is about60 degrees particularly sensitive to the flame spectrum