Gas-sensing system based on the cyclic temperature

Distinguishing Among Gases with a Semiconductor Sensor Depending on the Frequency Modulation of a Cyclic Temperature

“…(1) A fundamental harmonic (frequency: f 0 ¼ 0.08 Hz) voltage (V a ) was generated with a waveform generator (NF Electronic Instruments, WF1946, Japan) and supplied to the heater of a semiconductor sensor. Under this condition, the timevariation of temperature was almost sinusoidal [21]. The time-variation of the output conductance as the sensor response was characteristically deformed from the sinusoidal input signal of temperature depending on the sample gas, i.e., the plot of sensor temperature versus sensor conductance was characteristically deformed from an ellipsoid.…”

“…The characteristic nonlinear responses of a semiconductor gas sensor under the application of temperature perturbation including frequency modulation were not only evaluated by a polynomial approximation but also calculated based on a reaction-diffusion model for the solid surface. Figure 1 shows a schematic representation of the experimental apparatus developed from our previous system, and processes (1) and (2) were performed [3,16,21,22]. Process (2) was developed in this paper.…”

1.4.3 The EMD Based IMF Analysis of Gas Sensor Dynamic Signals

“…This leads to the development of response patterns, which are characteristic of the species being detected. By retrieving information from response dynamics, new response features are obtained that confer more selectivity to metal oxide sensors [1][2][3][4]. In deed, several authors have developed this strategy and applied several techniques to extract features that important for the discrimination or quantification of gases.…”

“…In deed, several authors have developed this strategy and applied several techniques to extract features that important for the discrimination or quantification of gases. Very often Fast Fourier Transform and Discrete Wavelet Transform have been used as feature extraction tools [3][4]. However, most features extracted are more related with the pattern recognition approaches than sensors, and their meanings are not easy to analyze.…”

Distinction of gases with a semiconductor sensor depending on the scanning profile of a cyclic temperature

“…To overcome this problem, a time-dependent sensor response under temperature modulation has been developed, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] in addition to the strategy of using sensor arrays. 20 We have been developing a gas-sensing system based on the dynamic nonlinear response under a cyclic temperature [21][22][23][24][25][26][27][28] or cyclic diffusion 29 to obtain multi-dimensional information in addition to one-dimensional information under a steady state. We have reported that the nonlinear dynamic response of a gas sensor changes characteristically depending on the concentration and chemical structure of gas molecules, and these characteristic responses can be qualitatively reproduced by a numerical simulation based on the kinetics of gas molecules (diffusion, adsorption, and reaction) on the sensor surface.…”