Robert Boschgmbh

Dietmar Blessing

Erich Junginger

Rene Schenk

Christian Zimmermann

Johann Riegel

Wolfgang Kosak

Guenter Braun

Bernd Hilgenberg

Margit Mueller

Wilhelm Haag

Frank Molwitz

For achieving a highest possible measuring accuracy of a circuit for measuring the internal resistance of an exhaust-gas sensor, a method and a circuit for measuring the internal resistance R() of an electrochemical cell () are provided for determining the temperature of an exhaust-gas sensor, especially of a motor vehicle. The circuit is provided with the objective to improve the control to a constant temperature to therefore also improve the performance of the exhaust-gas sensor. A measurement current I_Mess () is applied to the internal resistance R() of the electrochemical cell () and a resulting first voltage is detected. A switchover to a reference resistor Rtakes place from time to time or at regular time intervals. With a switchover to the reference resistor R, the resulting second voltage is stored and thereafter is applied as a reference value for the measurement of the internal resistance R(). The switchover () to the reference resistor Rtakes place, for example, via force/sense lines.

Determining the temperature of an exhaust gas sensor by means of calibrated internal resistance measurement

A method is distinguished in that outside of the analog/digital converter, on the basis of an analog signal (UA) to be digitized by the analog/digital converter, a sequence of digital pulses (P2) is generated, of which at least the width or the repetition frequency is analog signal-dependent, and that a digital result determined based on the pulse sequence and the digital value generated on the basis of the same analog signal by the analog to digital converter are checked for conformance with one another. As such, in a simple manner, a continuous monitoring of the A/D converter to be monitored is rendered possible during its 'normal' operation.

Method for monitoring the operability of an analog to digital converter

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Holzgerlingen, Germany

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