INTELLECTUAL SENSING BASED ON NONLINEAR D YNAMICS - MEASUREMENT OF COMPONENTS BY TIME-DEPENDENT RESPONSE OF A SEMICONDUCTOR GAS SENSOR

By processing multi-dimensional information involved in nonlinear dyna mical response, we propose an intellectual process to imitate the high ability of chemical sensing in living organisms. As an example of the application, we show an experimental result on gas sensing when a sin usoidal voltage is applied to a heater inserted into a SnO2 gas sensor . The nonlinearity in the resulting output resistance of the gas senso r is evaluated by using the algorithm of the fast Fourier transformati on (FFT). It is demonstrated that one can distinguish small difference in the chemical structure in alkanes and alkenes, based on the inform ation in the higher harmonics of the FFT.