Vapor supply method in odor sensing system and analysis of transient sensor responses

In an odor sensing system, a flow-type measurement system has been used to supply odorant vapors to the sensor cell since the measurement system is quite simple and enables the rapid measurement. Although we have used the peak frequency shifts of QCM gas sensors during the vapor exposure as the sensor outputs, the shapes of the transient responses may be useful to discriminate odor samples. Moreover, the sensing system should be robust when the measurement condition such as supplied vapor concentration fluctuates. Then, we proposed pulse vapor supply method and modelled the measurement system to extract the information for odor identification. Since the variation of the vapor concentration could be ignored in the pulse vapor supply method, the system model became simple enough to be robust to the fluctuation. The pattern separation among various samples with artificially fluctuated concentrations was improved when the model parameters of transient responses after the pulse vapor supply were used.