Abstract: A method for determining the reducing agent concentration (NH3) in the exhaust-gas flow of an internal combustion engine, using a zeolitic NH3 gas sensor that supplies a base measuring value, which is initially corrected by an offset value and a correction value that depends on the H2O concentration of the exhaust gas to form an intermediate value. The intermediate value is subsequently corrected by an additional value that depends on the NOx and NH3 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 NOx concentrations >500 ppm, extremely low NH3 concentrations <20 ppm or high NH3 concentrations >100 ppm.

Abstract: A method for determining the reducing agent concentration (NH3) in the exhaust-gas flow of an internal combustion engine, using a zeolitic NH3 gas sensor that supplies a base measuring value, which is initially corrected by an offset value and a correction value that depends on the H2O concentration of the exhaust gas to form an intermediate value. The intermediate value is subsequently corrected by an additional value that depends on the NOx and NH3 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 NOx concentrations >500 ppm, extremely low NH3 concentrations <20 ppm or high NH3 concentrations >100 ppm.

Abstract: 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.