Patent ID: 6776890
Filing Date: 2004-08-17
Classification: G01N

Abstract:
A circuit arrangement for carrying out a method for operating a mixed-potential exhaust-gas probe for an internal combustion engine wherein exhaust gas is generated, the exhaust-gas probe including: a heatable probe ceramic; a first electrode arranged in a chamber subjected to a reference atmosphere; and, a second electrode, which detects gas molecules, and is arranged in the exhaust gas of the internal combustion engine; the method comprising the steps of: providing a pump voltage source and applying a pump voltage across the first and second electrodes so that, in the interior of the chamber, a reduced oxygen partial pressure relative to the oxygen partial pressure in the exhaust gas is adjusted by the electrochemical pumping off of the oxygen molecules and the voltage across said first and second electrodes deviating from the thermodynamic equilibrium voltage of the reaction which takes place in said exhaust-gas probe; and, measuring and evaluating the current flowing across the electrodes; the arrangement comprising:an inverting operational amplifier having a non-inverting input, an inverting input and a feedback loop; a voltage divider R2 connected to said non-inverting input; the exhaust-gas probe being connected to said inverting input; a reference resistor R1 arranged in said feedback loop; and, a differential amplifier which amplifies the voltage difference between said non-inverting input and the output of the operational amplifier and outputs the difference as a measurement signal.