An important instrument in the development of gas sensor systems and pattern recognition methods is the test and measurement system itself. Whereas for a calibration of commercial gas sensors prefabricated gas mixture were often uses, research purposes need a more flexible system. The test system of the Fraunhofer-Institute for Solid State Technology (IFT) provides independent mixing of two test gases together with a humidification at a high dynamic range. Gas mixing is performed via volumetric method. An overview about the calculations necessary for the volumetric mixing is given. Two test chambers were developed, optimized for a small volume and a precisely defined gas stream. These test chambers simultaneously contain up to ten sensors of different types (semiconductor, dielectric, microbalance, ...) and provide measurements of gas temperature and pressure. The exhaust gases are analysed by a dew point mirror and an optional infrared gas analyzer to assure gas combination and accura cy of gas concentration. Measurements with semiconductor sensors, dielectric sensors and microbalances demonstrate the quality and flexibility of the test system.
