Flame monitoring system

Claim 1

Flame monitoring system for a burner, characterized by first flame radiation sensing means (10) responsrve to a first radiation wavelength range, said first means providing a first electrical signal indicative of flame radiation sensed at said first wavelength range; dissimilar flame radiation sensing means (11) -responsive to a different radiation wavelength range than said first means , said dissimilar means providing a second electrical signal indicative of flame radiation sensed at said different wavelength range; means for summing (14) said first and second electrical signals from said sensing means (10,11); filter means (15) for passing the AC flicker components and filtering out the DC components of the summed signals to provide an AC output sicnal; means (20) for rectifying to DC said first electrical signal to provide a third signal; non-linear amplifying means (21) for compressing the dynamic range of said third signal which may vary in intensity by orders of magnitude at the input, to provide an output signal which is a function of the input signal but compressed in dynamic range; divider means (16) having a dividend input and a divisor input, whereby said compressed signal is fed to the divisor input and said AC output signal is fed to the dividend input; and circuit means (17) connecting the output of the divider means to indicator means (18).