Burner flame sensing system and method

An apparatus for detecting the presence of a flame comprising:

• a sensor for detecting radiation produced by a flame and producing an electrical signal indicative of the radiation;
• an automatic gain controlled amplifier for amplifying the electrical signal;
• means for digitizing the electrical signal from said amplifier into a plurality of signal samples;
• means for storing the plurality of signal samples;
• means for transforming the signal samples from a time domain to a frequency domain to produce a plurality of component frequency amplitude values;
• means for deriving a logarithmic value for each component frequency amplitude value of the electrical signal;
• means for determining a degree of linearity of a distribution of the logarithmic values;
• and
• means for evaluating the degree of linearity to determine whether the flame is present.

A method for determining a characteristic of a flame comprising:

• detecting radiation at a frequency produced by a flame and producing an electrical signal indicative of the radiation;
• transforming the electrical signal from a time domain to a frequency domain to produce amplitude values for a plurality of component frequencies which result from shape changes of the flame with time;
• determining a degree of linearity of a distribution of the amplitude values;
• and
• employing the degree of linearity to determine a flame characteristic.