Patent ID: 7248357

Claim:
A system for measuring heat energy of a combustible fluid, the system comprising: radiation means for directing radiation through a sample of said combustible fluid; detection means for detecting an absorbance of at least one combustible component of said combustible fluid at a selected spectral line, there being at least one said spectral line for each said combustible component to be considered in said combustible fluid; a data processor comprising storage means for storing a plurality of spectra of combustible gas mixtures and for comparing said plurality of spectra to a measured absorbance spectrum, combination means for combining at least one heat energy proportional factor with said absorbance at each said spectral line, and summing means for summing said combinations to determine said heat energy of said combustible fluid; and calibration means for calibrating a source of said radiation, said calibration means comprising at least two focusing lenses, at least two light intensity detectors adapted to provide an output signal to said data processor, each said light intensity detector linearly aligned with one of said focusing lenses, and at least one narrow band interference filter disposed between, and linearly aligned with, each of said focusing lenses and said light intensity detectors.