Patent ID: 6763697
Filing Date: 2004-07-20
Classification: G01N

Abstract:
A device for operating a linear lambda probe of an internal combustion engine, comprising:an evaluation circuit which is connected to the lambda probe via its terminals, an oscillator which generates an oscillator signal having a frequency, and a measurement signal which is derived therefrom by means of frequency division and has a relatively low frequency which is fed to a first probe terminal, a first difference amplifier whose inverting input is connected to a third probe terminal and whose noninverting input is connected to a fourth probe terminal, a controller and a pump current source, a first capacitor in which a lower value of the sum voltage is continuously stored is provided, a second capacitor in which an upper value of the sum voltage is continuously stored is provided, a base point of the first and second capacitors being capable of being connected to a second probe terminal and being connected to a negative pole of a reference voltage, a positive pole of the reference voltage being connected to a positive pole of a center voltage, a decoupling amplifier is connected downstream of each of the other terminals of the first and second capacitors, wherein the outputs of the two decoupling amplifiers are connected to one another by means of a voltage divider whose tap is connected to a noninverting input of the controller, whose output is connected to the fourth probe terminal, and whose inverting input lies at the center voltage and is connected to the noninverting input of the pump current source, an inverting input of the pump current source is connected to the third probe terminal, and the output of the pump current source is connected to the second probe terminal.