A report discusses the second generation of the JPL Electronic Nose (ENose), an array of 32 semi-specific chemical sensors used as an event monitor to identify and quantify contaminants released into breathing air by leaks or spills. It is designed to monitor the environment for changes in air quality, and is trained to identify and quantify selected chemical species at predetermined concentrations, ranging from sub-ppm to ppth. This system has improved reproducibility for making matched arrays, allowing use of data analysis software with minimal recalibration on sensor set replacement. The Second Generation (SG) ENose is a follow- up to the first JPL Electronic Nose that was tested on an earlier space shuttle mission (STS-95). Improvements have been made to the hardware, sensor materials, and data analysis software.
The SG ENose can be adapted to different applications and analyte sets by selection of sensor sets. A monolithic chassis eliminates most fittings, tubing, and dead space, improving the flow system. The SG ENose also includes humidity and temperature sensors in the sensing chamber for improved event deconvolution. The design allows simple and rapid change-out of sensor sets and of filter material. All surfaces exposed to analyte are made of inert materials, and the unit is small enough to be handheld.