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.

A system includes: an exhaust aftertreatment system that includes a particulate matter sensor that includes a heating element configured to selectively provide heat to the particulate matter sensor; and a controller programmed to: receive particulate matter data indicating a state of the particulate matter sensor; determine that the particulate matter sensor is in a full state based on the particulate matter data; and activate the heating element to: (i) a first temperature for a first period of time, the first temperature being sufficient to burn off water or ammonia; (ii) a second temperature for a second period of time immediately after the first period of time, the second temperature being greater than the first temperature and being sufficient to burn off urea, biuret, or melamine; and (iii) a third temperature for a third period of time immediately after the second period of time, the third temperature being greater than the second temperature and being sufficient to burn off carbon.

A control device of an exhaust sensor comprises a heater control part configured to set a target temperature of an electrochemical cell and control a heater so that a temperature of the electrochemical cell becomes the target temperature, and a judging part configured to judge whether a water repellency of a protective layer is falling when the heater control part sets the target temperature to a temperature of a lowest temperature at which a Leidenfrost phenomenon occurs at an outer surface of the protective layer or more. The heater control part is configured to rise the target temperature when the judging part judges that the water repellency of the protective layer is falling.

With respect to a vehicle mass air-flow sensor that includes a temperature sensor for measuring a temperature of a sensor element of the mass air-flow sensor, a method for controlling a heating element for heating the sensor element of a mass air-flow sensor includes identifying a dew formation on the sensor element by evaluating a temperature profile that is recorded during an operation of the vehicle using the temperature sensor, and generating a switch-on signal for switching on the heating element in response to the identification of the dew formation.

Compensator circuitry is provided for an oxygen sensor which includes a pump cell and a reference cell. The compensator circuitry includes a feedback control loop which maintains the reference cell at a reference voltage. The feedback control loop includes a digital compensator which determines and outputs a compensation current to the pump cell dependent on a reference voltage measured from the reference cell. The digital compensator also suspends the determination and output of the compensation current for a set time which is dependent on detection of edges in an oxygen sensor heater Pulse Width Modulation signal.

A gas sensor includes a sensor element body having a porous layer provided on an outer surface, and a power supply device which supplies power to a heater element that is in the sensor element body. The amount of power being applied to the heater element by the power supply device when gas detection is being performed by the gas sensor in a steady state is designated as P [W], the volume of the length range of a heating region of the heater element provided in the sensor element body as V [mm.sup.3], and the applied power density as X [W/mm.sup.3], where X is a value expressed by P/V. In that case, the following relationship is satisfied between the applied power density X and the average thickness Y [m] of the porous layer:

Y509.322884.89X+5014.12X.sup.2

Systems and methods for operating an internal combustion engine that includes an oxygen sensor are described. In one example, a voltage that is applied to a heating element of an oxygen sensor is integrated to determine a resistance of the heating element. The resistance of the heating element is the basis for adjusting voltage applied to the heating element during subsequent engine starts.

Methods and systems are provided for adjusting heater power of an oxygen sensor. In one example, a method for an engine includes adjusting heater power of a heating element of the oxygen sensor when the heater power increases by a threshold amount. The method includes subsequently increasing heater power back to a baseline power level responsive to a temperature of the heating element.

A control apparatus is provided for controlling an exhaust gas sensor. The exhaust gas sensor includes a first cell, a second cell configured to output electric current depending on the concentration of a measurement target component in exhaust gas from which oxygen has been removed by the first cell, and a heater configured to heat the first and second cells. The control apparatus includes a heater controlling unit, a current detecting unit configured to detect the electric current outputted from the second cell, and a deterioration determining unit. The deterioration determining unit causes the heater controlling unit to change output of the heater and thereby changes the temperature of the first cell. During the change in the output of the heater, the deterioration determining unit determines, based on an amount of change in the electric current detected by the current detecting unit, whether or not the second cell is deteriorated.

In a method for diagnosing a particle filter of a motor vehicle a particle sensor which is connected downstream and has a ceramic sensor element is used, wherein, for the particle sensor, regeneration (10) of the ceramic sensor element is provided by thermal heating to a specific temperature and for a specific time after the start of the motor vehicle. Within the scope of an on-board diagnosis a confirmed diagnosis result is output after a repeated occurrence of a first diagnosis result. In the proposed method reduced regeneration (40) of the ceramic sensor element takes place after a first diagnosis result (30).