Modulated composition flame photometer

Claim 1

An improved flame photometer of the type wherein there is provided a flame chamber containing a burner for burning a stream of sample gas to be analyzed, an optical filter for passing specific spectral components of the luminosity and a photomultiplier for converting light energy to an electrical signal wherein the improvement comprises: a source of a reference gas; means for composition modulating said sample gas stream with said reference gas, said modulating means comprising: a cavity having a first input coupled to said source of reference gas, a second input for receiving said sample gas and first and second outputs for delivering said reference gas and said sample gas to said burner; a flexible diaphragm partitioning said cavity and separating said first input and said first output from said second input and second output; and means for imparting to said diaphragm a sinusoidal displacement to produce peak tidal flows of said sample gas and said reference gas to said burner equal to the reference gas and sample gas inflow rates; and means for measuring the amplitude of the periodic electrical signal corresponding to flame intensity variation occurring at the modulating frequency.