Abstract: An infrared emittance combustion analyzer utilizing detectors in a flame burner which monitor the radiation at two preselected wavelengths. The respective radiation signals are filtered to eliminate DC signal variations, rectified and converted into a DC value which is representative of the measured radiation signals. The respective DC values are formed into a ratio which is compared against a predetermined setpoint signal, and the error signal resulting from this comparison is utilized to drive an electromechanical controller which adjusts either the air damper or the fuel damper to adjust the fuel/air mixture which is fed into the burner.

Abstract: The linearity of a photoresistive device at varying levels of radiant signal is improved by masking the sensitive area of the photoresistive device so that only a portion of the sensitive area is illuminated. The masking prevents exposure of the entire surface area of the cell, which increases the dynamic range, allowing a more linear, small signal sensitivity over wide variations in brightness.

Abstract: The presence of a flame from a burner is determined by analyzing the signal produced by a radiation sensor aimed at a burner. Specifically, a Fourier transformation is applied to the signal producing amplitude values for a spectrum of component frequencies produced by changes in the power of the flame over time. A logarithmic value is derived for each of the amplitude values. The degree of linearity of the distribution of the component frequency logarithmic amplitude values provides an indication of the flame presence. Several parameters, including integrated linear error, linearity regression correlation and slope difference, provide an indication of the degree of linearity. A plurality of values for each of these parameters are produced during an interval of time.