Siemens Aktiengesellschaft

Continental Automotive Gmbh

Bertrand Lemire

Hans Meixner

Tim Walde

Susanne Kornely

Johannes Bentner

Willibald Schuerz

Hermann Leiderer

Muammer Kilinc

Dieter Hahn

Willibald Schurz

Sabrina Kolbeck

Birgitta Hacker

A method for operating a probe having a pumped reference cell. A pulse-width-modulated pump current is applied to the reference cell at a first point in time. In accordance with the first point in time, a first voltage characteristic value (representing the voltage applied to the reference cell) is determined within a first time frame. The pulse-width-modulated pump current applied to the reference cell is switched off at a second point in time. A third point in time is determined, at which a pulse-width-modulated pump current applied to the reference cell is switched off. In accordance with the third point in time, a second voltage characteristic value (representing the voltage applied to the reference cell) is determined within a second time frame. The first and second voltage characteristic values are used to determine a diagnostic characteristic value, which is representative of an error in determining the nitrogen oxide concentration.

Method for operating a probe

A gas measuring system, having a measurement sensor () which records an exhaust gas from an internal combustion engine and has an outer electrode (), which is exposed to the exhaust gas to be measured, a first measuring cell (), a second measuring cell () that is connected to the first measuring cell (), and in which a measuring electrode () is arranged, and a reference electrode () that is exposed to the ambient air. The measuring cells () are located in a solid electrolyte (), and all the electrodes () are in contact with the solid electrolyte. A circuit which in a first pump flow (Ip) pumps oxygen ions between the first measuring cell () and the outer electrode (), in a second pump flow (Ip) pumps oxygen ions between the second measuring cell () and the outer electrode (), and in a third pump flow (Ip) pumps oxygen ions between the measuring electrode () and the outer electrode (), and which comprises a control unit (C) which records Nernst voltages between the measuring cells () and a reference electrode ().

Device and method for measuring a plurality of exhaust gas constituents

A thick-film measurement sensor includes two measurement cells and is used to measure the NOx concentration in the exhaust gas from an internal combustion engine. The 1/&lgr; value of the exhaust gas is determined from an oxygen ion pump current flowing in the first measurement cell, for example, by a characteristic diagram, and, a measurement error, which can be used to correct the measured NOx concentration, is determined from this 1/&lgr; value, for example, by a characteristic curve that has previously been determined in a calibration measurement. The invention is based on the discovery that the measurement error is dependent on the air ratio in the exhaust gas. If this is expressed by the 1/&lgr; value, there is no need for a complex division calculation during the correction.

Method for determining a NOx concentration

A method and device for checking the functional ability of a catalyst in an exhaust duct of an internal combustion engine is described. The method and device determines a degree of conversion as a function of the temperature of the catalyst during a heating-up phase. Evaluation of the relationship between the degree of conversion and the temperature, the relationship changing with the age of the catalyst, allows a non-functional catalyst to be checked and diagnosed with high accuracy.

Method and device for monitoring the functional ability of a catalyst of an internal combustion engine

A porous Al.sub.2 O.sub.3 thick film covers the SrTiO.sub.3 layer of an oxygen sensor, said SrTiO.sub.3 layer being contacted by means of two Pt electrodes and deposited on an Al.sub.2 O.sub.3 substrate. The electrically insulating Al.sub.2 O.sub.3 layer bears a protective layer, which is exposed to the exhaust gas and is preferably also made of SrTiO.sub.3. This construction ensures that the output signal of the sensor representing the oxygen partial pressure then depends only on the resistance or, respectively, conductivity value of the non-contaminated SrTiO.sub.2 sensor layer.

Gas sensor

A method for testing the functional capability of a catalytic converter of an internal combustion engine uses an exhaust-gas probe having a measuring electrode for measuring the resistance of a metal oxide layer having low catalytic activity. The resistance of the metal oxide layer is dependent on the oxygen partial pressure in the exhaust gas, for a predetermined air factor. The conversion rate of a catalytic converter has an effect on the oxygen partial pressure in the exhaust gas downstream of the catalytic converter, so that the resistance of the metal oxide layer depends on the conversion efficiency of the catalytic converter. It is thus possible to test the functional capability of the catalytic converter with the simply constructed exhaust-gas probe using a simple resistance measurement.

Method for testing the functional capability of a catalytic converter

An exhaust gas sensor has first and second sensor elements. Exhaust gas surroundings of the first sensor element are catalytically activated, so that an oxygen partial pressure which is in equilibrium will always be measured by the first sensor element, regardless of the conversion capability of a catalytic converter. The exhaust gas surroundings of the second sensor element are separate from the exhaust gas surroundings of the first sensor element, so that the exhaust gas surroundings of the second sensor element are not catalytically active. As a function of the conversion capability of the catalytic converter, the second sensor element measures either an equilibrium oxygen partial pressure or a free oxygen partial pressure, which are of different magnitudes. A malfunction of the catalytic converter is detected by comparing measurement signals of the first and second sensor elements.

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Schierling, Germany

Bertrand Lemire