Distinction of gases with a semiconductor sensor under a cyclic temperature modulation with second-harmonic heating

A gas-sensing system based on a dynamic nonlinear response is reported to improve the selectivity in a sensor response toward sample gases. A cyclic temperature modulation composed of fundamental and second-harmonic heater voltage was applied to a SnO2 semiconductor gas sensor and the resulting conductance of the sensor was analyzed by fast Fourier transformation (FFT). The dynamic nonlinear responses to hydrocarbons and alcohols were further characterized depending on the phase of the second-harmonic heater voltage (θ2).