Device for analysing exhaust emissions from motor vehicles

The invention relates to a device for analysing the most important environmentally relevant substances such as CO,HC and NO in exhaust fumes from motor vehicles, based the principle of IR gas absorption. Measuring signals and a reference signal are picked up along an optical measuring distance (special steel tube) using an infrared source and a detector and a measuring value is determined by forming quotients. The OBM system consists of modular components such as a removal device, an exhaust gas processor, an analysis device and an evaluation unit which are integrated into the construction of the motor vehicle. Vibratory conditions in the motor vehicle are compensated by a robust design structure and correction of temperature drift by forming a first derivation and adjustment of the signal height by electronically adjustable amplification regulation. Other correction options are calibration of the zero line with ambient air during switching operations in addition to the creation of a range of tolerance around the noise signals in the detector. The measuring system is to be fitted in the future in all motor vehicles as an addition to the existing OBD (On board Diagnosis) system. Retrofitting devices can be used for older vehicles.