Patent ID: 8221613
Filing Date: 2012-07-17
Classification: G01N

Abstract:
1. A gas-measuring system, comprising: a measurement sensor configured to record an exhaust gas from an internal combustion engine, the sensor having an outer electrode exposed to the exhaust gas, a first measuring cell, a second measuring cell that is connected to the first measuring cell, a measuring electrode arranged within the second measuring cell, and a reference electrode exposed to ambient air, the first measuring cell and the second measuring cell being located in a solid electrolyte, the measuring electrode and the reference electrode being in contact with the solid electrolyte, and a circuit operative to provide a first pump flow of oxygen ions between the first measuring cell and the outer electrode, a second pump flow of oxygen ions between the second measuring cell and the outer electrode, and a third pump flow of oxygen ions between the measuring electrode and the outer electrode, a control unit operative to record and evaluate Nernst voltages between a first electrode on the first measuring cell, a second electrode on the second measuring cell, the measuring electrode and the reference electrode and the circuit being operative to control the second pump flow to a desired value based on an evaluation of the Nernst voltages recorded, wherein the control unit can be switched between a first operating mode and a second operating mode, the desired value for the second pump flow being higher in the first operating mode than in the second operating mode, the control unit, in the first operating mode, being configured to regulate second and third Nernst voltages and the second pump flow to constant values by changing the first and third pump flows, and to set a lean mixture in the first measuring cell so that nitrogen oxides are not reduced in the first measuring cell, whereby a measurement signal for an oxide content in the exhaust gas is derived from a value of the third pump flow and, in the second operating mode, being configured to control a desired value of the second Nernst voltage and the desired valve of the second pump flow so that a different predetermined first Nernst voltage is set in the first measuring cell, whereby a measurement signal for an oxygen content or a lambda value of the exhaust gas is derived from the first pump flow, and a control input operative to switch between the first operating mode and the second operating mode.