Daimler Chrysler Ag

Conti Temic Microelectronic Gmbh

Eckard Irion

Aleksandar Knezevic

Holger Leye

Mirko Smuk

A method for determining the reducing agent concentration (NH ) in the exhaust-gas flow of an internal combustion engine, using a zeolitic NH gas sensor that supplies a base measuring value, which is initially corrected by an offset value and a correction value that depends on the H O concentration of the exhaust gas to form an intermediate value. The intermediate value is subsequently corrected by an additional value that depends on the NO and NH concentration of the exhaust gas. In particular at or above the limits for the operating range, the accuracy of the method increases for one of the following conditions: gas compositions with NO concentrations >500 ppm, extremely low NH concentrations <20 ppm or high NH concentrations >100 ppm.

Method for determining the reducing agent concentration (NH3) in the exhaust-gas flow of an internal combustion engine

A capacitive sensor for measuring a characteristic of a fluid or a filling depth of a liquid in a container is constructed of a printed circuit board that is either flexible or has stiff and flexible sections along its length. Metal coatings forming capacitor plates are formed, for example by printed circuit techniques on one or both sides of the circuit board which is then bent into such a configuration that two capacitor plates forming a capacitor face each other across a spacing that is accurately maintained by spacers. The bent shape of the circuit board has, for example, a U-configuration, an inverted S-configuration, or an e-configuration. Additional metal coatings are provided for screening purposes against adverse field influences. Conductor leads are provided on the printed circuit board for connecting the capacitor plates to an evaluating circuit, and the metal screens to a reference potential such as ground. The bent circuit board is held in position in a frame that itself may form a housing provided with openings for the inflow and outflow of the fluid which forms a dielectric between the capacitor forming plates. Lateral and vertical movement of the bent circuit board is further restrained by position fixing pins.

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Waldenbuch, Germany

Eckard Irion