Calibrating nitrogen oxide sensor in engine exhaust system, shuts off engine for interval during which decay of nitrogen oxide signal is observed and evaluated

摘要

From To to To + delta , the engine is shut off. For a given interval, up to To + delta , the decay behavior of the NOx signal is evaluated. From the result, a correction parameter for the NOx signal is determined. The correction parameter is an offset value. Before and/or after To, values of a given operational parameter of the exhaust are determined. Evaluation only takes place when values determined lie within given operational regions. A variant of the procedure according with the foregoing principles is also described. The operational parameter is an nitrogen oxides (NOx) sensor (9, 10) temperature, an exhaust gas mass flow rate at the sensor, an NOx concentration measured by it and/or an air ratio at the NOx sensor. Measurements are taken of the NOx fluctuations and its decay curve. A parametric-, exponential- or polynomial function is fitted to the curve. An independent claim is included for corresponding instrumentation and equipment.