Patent ID: 7680607

Claim:
A method of analyzing a chemical analyte, said method consisting of the steps of: generating a fluctuation output signal in response to a plurality of resistance fluctuations of a Metal Oxide Semiconductor (MOS) gas sensor; adjusting current flow through said sensor using a biasing circuit to achieve current differentials sufficient to detect different analytes, and sufficient for obtaining a measurement of said fluctuation output signal; normalizing said measurement of said fluctuation output signal for current differentials by dividing by the standard deviation of a time series of sampled current; and transforming said fluctuation output signal into a bispectrum signal represented by the bispectrum function S 3 ⁢ x ⁡ ( f 1 , f 2 ) = ∑ k = - ∞ ∞ ⁢ ⁢ ∑ l = - ∞ ∞ ⁢ ⁢ C 3 ⁢ x ⁡ ( k , l ) ⁢ ⅇ - j ⁢ ⁢ 2 ⁢ π ⁢ ⁢ f 1 ⁢ k ⁢ ⅇ - j ⁢ ⁢ 2 ⁢ π ⁢ ⁢ f 2 ⁢ l using positive and negative values for frequencies f 1 and f 2 of said bispectrum function; establishing a contour graph that is representative of the results of said transforming step, said contour graph created using said positive and negative values for said frequencies f 1 and f 2 ; comparing said contour graph to a database of reference contour graphs, said reference contour graphs created using said positive and negative values for said frequencies f 1 and f 2 corresponding to known analytes; generating an analyte output signal that identifies a characteristic of said analyte; and determining if said contour graph utilizing said positive and negative values for said frequencies f 1 and f 2 corresponds to one of said reference contour graphs from said database.