Methods and systems are provided for reducing blackening of an oxygen sensor due to voltage excursions into an over-potential region. Before transitioning the sensor from a lower voltage to an upper voltage during variable voltage operation, an operating temperature of the sensor is reduced via adjustments to a sensor heater setting. The reduction in temperature increases the range of temperatures available to the sensor before the over-potential region is entered.

A method for NOx emission control during start of a vehicle comprising an exhaust aftertreatment system, an engine, and a NOx sensor is provided. The method includes determining a temperature of the NOx sensor; if the determined temperature of the NOx sensor is below a predetermined threshold, initiating heating of the NOx sensor, and performing a preventive action for delaying engine start until a determined temperature of the NOx sensor exceeds or is equal to the predetermined threshold.

A gas sensor element comprising a long plate-like element body and a porous protective layer protecting a surface of the element body, wherein the element body has a gas detection part at an end thereof on one end face side in a longitudinal direction, and the protective layer includes an end face part covering the one end face in laminate, side face parts covering side faces connected to the one end face in laminate, and corner parts where two adjacent ones of the end face part and the side face parts meet. An outer surface of one or more of the end face part and the side face parts has a concave shape that is smoothly continuous with the corner parts and configured such that a layer thickness increases toward the corner parts.

The present invention provides a heater temperature control circuit including a heater and a control circuit that controls a temperature of the heater, wherein the control circuit includes a bridge circuit in which a first circuit and a second circuit are connected in parallel, and an operational amplifier connected to the bridge circuit, wherein in the first circuit, the heater and a resistor are connected in series, and a midpoint of the first circuit is connected to one input portion of the operational amplifier, and an output value V.sub.out from the second circuit is input to the other input portion of the operational amplifier, the output value V.sub.out being obtained by multiplying a division ratio of a target resistance value R.sub.h of the heater and a resistance value R.sub.1 of the resistor with a reference voltage V.sub.ref of the bridge circuit.

Various embodiments of the teachings herein include a method for determining a state parameter of an exhaust gas sensor with a sensor element and a heating device arranged in the sensor element for heating the sensor element. The heating device is electrically connected via a first electrical line and a second electrical line to a control device for electrically controlling the heating device. The heating device includes a measuring line electrically connected between the control device and the first electrical line for controlling the temperature-dependent resistance of the heating section. The method may include: determining a measurement voltage dropped between the first electrical line and the measuring line; determining a compensation voltage on the basis of a predetermined reference voltage and the determined measurement voltage; and determining the state parameter of the exhaust gas sensor by assigning the determined compensation voltage to the state parameter.

A method for diagnosing a heating element of an exhaust gas sensor of an internal combustion engine. The exhaust gas sensor includes a temperature measurement device. A modeled temperature at the point of the exhaust gas sensor is continuously ascertained with the aid of a temperature model. The temperature of the exhaust gas sensor is increased by a heating process. The diagnosis of the heating element of the exhaust gas sensor is provided as the result an enable condition. Upon enablement of the diagnosis, a temperature difference between the modeled temperature of the exhaust gas sensor and the measured temperature of the exhaust gas sensor are ascertained. The heating element of the exhaust gas sensor is recognized as defective when the ascertained temperature difference exceeds a predefinable temperature threshold value.

A method for operating an exhaust gas sensor in an exhaust system of an internal combustion engine of a vehicle. The exhaust gas sensor includes a ceramic sensor element having at least one measuring electrode and a heating device. A binary dewpoint end signal is calculated, based on data which relate to the internal combustion engine and the exhaust gas sensor, which indicates whether or not the occurrence of liquid water in the exhaust system is still to be expected. Whenever the vehicle is turned off and the dewpoint end signal simultaneously has the value which signals that the occurrence of liquid water in the exhaust system is still to be expected, the sensor element is heated by its heating device to a temperature for a certain period of time in such a way that the sensor element dries.

To provide a sensor control device capable of identifying a short circuit terminal with a simple configuration and whose identification operation is not easily affected by environmental conditions around the sensor. The sensor control device includes a short circuit detection unit that detects a short circuit of a sensor having a plurality of terminals, a resistance value control unit that increases a resistance value of an element between the terminals when the short circuit of the sensor is detected by the short circuit detection unit, and a short circuit terminal identification unit that identifies at which of the plurality of terminals a short circuit occurs when the resistance value control unit increases the resistance value of the element between the terminals to a set value or greater.

The present invention obtains a humidity measuring device capable of performing self-diagnosis with high reliability. This humidity measuring device 20 has a diagnosis processing unit 25 for performing self-diagnosis by using gas temperatures and gas humidities before and after a gas in an ambient atmosphere to be measured is heat-controlled. The diagnosis processing unit has a diagnosis start determining unit 26 for determining whether the self-diagnosis can be started on the basis of an exchange state in the ambient atmosphere to be measured and the gas temperature and the gas humidity before the gas in the ambient atmosphere to be measured is heat-controlled, and a diagnosis continuation determining unit 28 for determining whether the self-diagnosis can be continued on the basis of the gas temperature and the gas humidity that are heat-controlled during the self-diagnosis.

A control and evaluation unit for the operation and evaluation of at least one sensor, in particular for the operation and evaluation of at least one lambda probe of an internal combustion engine, signal inputs being disposed for the reception of analog measured signals of the at least one sensor, received analog measured signals being digitized by way of an analog/digital converter, a signal transfer unit, by way of which digitized signals are transferred to a calculation unit, being disposed, and provision being made in particular that the signal inputs are switchable by way of a multiplexer.