Design of a Portable E-Nose Instrument for Gas Classifications

In this paper, a portable instrument is developed for a qualitative discrimination among different gas samples. The system is able to implement various gas measurement protocols entered by a user, display incoming online samples during an observation, and display classified gas sets from several observations. The system comprises the following: 1) an input unit, which is a quartz sensor array in a cell with microcontroller circuitry for sampling and data transfer; 2) a computational unit, which is a dedicated computer administrated with specially coded software; and 3) an output unit, which consists of relays for controlling gas valves and a liquid crystal display (LCD) for data presentation. The sampling circuitry is programmed using a low-level language, and the computer is programmed using a high-level programming language. The operating system is specifically configured to obtain a dedicated system. The distributed components of the system (the sampler, the display, and the application processes) are automatically started when the system is turned on. The system can easily be moved to a site where a gas observation is required. The system is extensively tested in a laboratory environment for the qualitative and quantitative properties of three industrial gases: acetone, chloroform, and methanol. Reasonably good results are obtained during both tests, e.g., the system successfully classified different species in qualitative tests and different concentration amounts in quantitative tests.