Analysis of QCM gas sensor transient response by visualizing gas concentration

Gas‐source localization systems are required to quickly detect gas concentrations at various locations while moving. It is therefore necessary to design the system by taking account of the delay in the response and recovery of the gas sensor in the presence of variations in gas concentration. Also, in order to model the dynamic characteristics of the gas sensor in open air, it is essential to understand the delay in response and recovery of the gas sensor. To carry out a transient response analysis of such a gas sensor, it is necessary to know the gas concentration (changing in time) at the gas sensor. In the present study, in order to analyze the transient response of a QCM (quartz crystal microbalance) gas sensor, the gas concentration is visualized. A photodiode is placed close to the gas sensor and the intensity of scattered laser light is measured optically in order to know the concentration of the gas passing over the sensor. The sensor response and the intensity of scattered light are measured simultaneously and the sensor response is estimated from the visualized gas concentration by means of the models of a second‐order system and a neural network. When the measured results and the estimated results are compared, the model based on the neural network is found to estimate more accurately. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(6): 14–21, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10062