Device for analyzing exhaust emissions from motor vehicles

This description refers to a device for analyzing the most important environmentally relevant substances, such as CO, HC and NO, that are present in vehicle exhaust emissions. It is based on the principle of IR gas absorption. This involves producing measuring signals and a reference signal in a measured optical length (stainless steel tube), with the aid of an infrared source and detector. The production of a ratio then gives a reading and a warning signal is produced whenever a certain limit value is exceeded. The OBM system is made up of modular components, such as a sampling device, exhaust gas processing unit, analyzing device and evaluation unit, which are built into the vehicle. The fluctuating conditions present in the vehicle are compensated for by robust construction and correction of temperature drift by means of production of the first derivation and readjustment of signal strength using an electronically regulated amplification control. Further correction possibilities are: calibration of the zero line using ambient air via a switchover system, and the establishment of a tolerance limit around the noise signals in the detector. The measuring system should in future be installed in all motor vehicles as an extension to using OBD (on board diagnosis) systems. Modification kits are available for older vehicles.