Specific detection of various organic solvents by means of sensor arrays with internal reference for facilitated calibration (PEGAS)

摘要

An array of semiconductor gas sensors is being optimized for qualitative and quantitative detection of several organic solvents. Depending on the substance, the detection ranges vary from 0-100 ppm to 0-1000 ppm. The problem of common electronic "noses" for practical industrial use is that the required accuracy can only be achieved by frequent re-calibration with a considerable number of different test gas mixtures and concentrations. The arrays developed in the PEGAS project include, as an internal reference, a narrowband infrared sensor, which is adapted to the application. The signal curves of the reference sensor for the solvents to be detected, are stored in the gas warning system and will be taken for comparison with every detection process. During the re-calibration the system determines for every individual sensor and for the whole array the signal relation to the reference sensor. Thus it can recognize and compensate the different drift and ageing effects occuning at individual sensors. Without the internal reference these effects could only be compensated by an extremely higher quantity of calibration gas mixtures. A further emphasis of the PEGAS project is the aspect of using the arrays for safety applications. For the signal evaluation it must be made sure that the presence of a strange combustible gas (which is not supposed to appear in the application) creates danger report, even if the quality of the substance is not detected. Any ambiguity of the signal evaluation must result in a danger report.