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 infrared receiving tube to detect flame thermal radiation, and 
then the flame brightness changes into high and low level signal, again 
through the comparator compared with reference voltage threshold, 
reaches
the 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 about
60 degrees, particularly sensitive to the flame spectrum