Abstract: The invention is directed to a circuit for conditioning the output signal of a measuring sensor for further processing in a control apparatus which has a fixed ground potential which does not necessarily correspond to the ground potential of the measuring sensor. A conditioning circuit is provided which can be integrated on a chip and has the following characteristics. The conditioning circuit compensates for the fluctuating ground offset between exhaust gas probe and control apparatus ground when utilizing an exhaust gas probe burdened with a potential. The circuit arrangement includes an external circuit which can be changed to influence the input signal to the conditioning circuit. With this changeable external circuit, the output signal of the circuit arrangement can be so modified that the control apparatus outputs an output voltage with offset and an output voltage without offset.

Abstract: The monitoring circuit for a sensor connected to a low-potential and high-potential line, such as a thermal element, includes a high-resistance pulldown resistor connected between the high potential line and ground, a offset voltage source connected to the low-potential line to supply an offset voltage higher than a minimum transistor control voltage; first and second testing transistor shaving control electrodes connected to respective ones of the lines via resistor arrangements; and a third testing transistor having a control electrode connected to an output of a p-type channel FET having a control electrode connected to one of the two sensor lines. Whether the operating state of the sensor is normal, involves a short circuit to ground or the supply voltage or an interruption of the sensor lines is determined by monitoring the switching states of the first testing transistor and a series combination of the second and third testing transistor.