EP3155411A1

EP3155411A1 - Method for operating a sensor apparatus

Info

Publication number: EP3155411A1
Application number: EP15729362.2A
Authority: EP
Inventors: Bernhard Ledermann; Ronaldi Rusli; Rolf Reischl
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-06-13
Filing date: 2015-05-29
Publication date: 2017-04-19
Also published as: KR20170018328A; WO2015189055A1; CN106461599B; DE102014211321A1; CN106461599A; KR102383817B1

Abstract

A method for operating a sensor apparatus (110) is proposed. The sensor apparatus (110) has at least one sensor element (112) for sensing at least one portion of a gas component in a gas in a measuring gas chamber (114). The sensor element (112) comprises at least one first electrode (116) and at least one second electrode (118). The second electrode (118) is arranged in at least one measuring cavity (120). The measuring cavity (120) can be supplied with gas from the measuring gas chamber (114) via at least one diffusion barrier (122). The first electrode (116) and the second electrode (118) are connected by means of at least one solid electrolyte (124) and form a pump cell (126). The sensor apparatus (110) additionally has at least one controller (128). The controller (128) is connected to the first electrode (116) by means of at least one first signal line (130). The controller (128) is connected to the second electrode (118) by means of at least one second signal line (132). The first signal line (130) is connected to an electrical earth (136) by means of at least one first interference suppression capacitance c1 (134). The second signal line (132) is connected to the electrical earth (136) by means of at least one second interference suppression capacitance c2 (138). At least one measuring resistor (140) is arranged between the electrical earth (136) and at least one from the first signal line (130) and the second signal line (132). The controller (128) is set up to operate the pump cell (126) with a function current. The method involves application of a plurality of different switching states to the pump cell (126) in order to determine the first interference suppression capacitance c1 (134) and the second interference suppression capacitance c2 (138).

Description

Description title

Method for Operating a Sensor Device State of the Art In principle, methods for operating a motor are known from the prior art

Sensor device known. With such a sensor device, a qualitative and / or quantitative detection of a gas component of a gas, in particular a detection of a gas component in an air-fuel mixture. Alternatively or additionally, however, other properties of the gas can also be detected with such a sensor device, for example any physical and / or chemical property of the gas. Also, several properties of the gas can be detected in principle. In particular, such

Sensor devices are used in the automotive field. The gas may be, for example, an exhaust gas in a measuring gas chamber of an internal combustion engine, in particular in the motor vehicle sector, and in the measuring gas chamber

for example, an exhaust tract.

Such sensor devices may include a sensor element for detecting at least a portion of a gas component of a gas. For example, a sensor element can be designed as a lambda probe as described in Konrad Reif (ed.) "Sensors in the Motor Vehicle", 2nd edition 2012, pages 160-165 A lambda probe can be used to determine a gas component of a gas mixture in a combustion chamber, for example the air ratio λ, which indicates the air / fuel ratio. With

Two-point lambda probes is a determination of the air-fuel ratio only in a narrow range, with stoichiometric mixtures (λ = 1) possible. By contrast, with a broadband lambda probe, which generally operates on the principle of a pumping cell, preferably connected to a Nernst electrochemical cell, a determination can be made over a large range of λ. Such ceramic sensor elements are based on the use of electrolytic properties certain solids, in particular on ion-conducting properties of these

Solids. These sensor elements usually comprise a ceramic

Solid electrolyte preferably of zirconium and / or yttrium or also

Solid state layers preferably of zirconium dioxide.

Such a pumping cell may consist of two connected via a solid electrolyte

Electrodes, in particular an inner and an outer pumping electrode, are formed. In principle, the sensor device can have a controller which is set up to apply a pumping current to the pumping cell. For example, a sensor element can be operated with a direct current or in a pulse mode.

For example, DE 10 2008 001 697 A1 describes that the pumping current is a

Pulse-shaped pumping current with a fixed frequency, a variable

Duty cycle and an adjustable sign can be. An operation of a

Sensor element with such a pumping current can as pulse operation of

Sensor element are called.

In principle, in signal lines, for example in a cable harness of the sensor device, suppression capacitances for protection, for example against static

Charges, an electronics of the sensor device may be provided. From DE 10 2010 000 663 A1 is known that for the attenuation of radio frequency interference and

High voltage inputs between signal lines of the broadband lambda probe and the earth capacitors may be provided. In a pulsed operation of

Sensor element, these capacities can be reloaded constantly. A charge transfer current flows in part via the pump cell of the sensor element and increases or decreases the pump current and must be taken into account in a characteristic calibration.

Furthermore, in DE 10 2010 000663 A1 a method for calibrating a

Umladekorrekturkennlinie described. By a periodic change between two switching states Z_1 and Z_2 is caused to an inner

Pump electrode terminal IPE and at an outer pumping electrode terminal APE the broadband lambda probe a pulse-shaped pumping current l _SQ is applied. The

Switch positions Z_1 and Z_2 thereby enable an edge-triggered measurement of the voltage drop U _G ND across the resistor R _G ND for calibration of the charge-over correction. The reloading of the capacitors is due to the flow of current through the

Resistor R _G ND off. The voltage drop across the resistor R _G ND voltages U _gua for the switching position Z_1 and U _gui for the switching position Z_2 therefore contain Umladeinformationen. The charge-reversal current d 1 _um is the most important component for the calibration and is calculated in DE 10 2010 000663 A1 by d 1 _um = F _um - (U _gui -U _gua / RGND _S ), _where F _um = T _sd / T _p . In this case, T _{sd is} the duration of the measurement conversion (integration time), T _{p is} the duration of the clock period of the pulse operation, and R _G ND _{s is} the nominal value of a resistor.

Basically, without taking into account the _{recharge current} l _pum a medium

_Pump current I _{p0 can be calculated} from a set effective duty cycle IPS and the measured current of a constant current source of the sensor device I _sq : I _p0 = IPS-I _sq , where the effective duty cycle IPS = (T _p -T _m ) / T _cydus . T _cydus is the duration of a measurement cycle, for example T _cydus = 666 με. T _p and T _m are each the duration of exposure of the sensor device with a positive or with a negative current pulse. With consideration of the _{charge-reversal} current l _pum , an average pump current l _{p can be determined} from l _p = l _p0 + l _pum . In the measuring cycle, the sensor device can be subjected to three switching states, wherein in a first switching state, the sensor device with a positive

Current pulse, in a second switching state, the sensor device with a negative current pulse and in a third switching state, the sensor device with a pulse pause, in which the sensor device is supplied with no current, can be acted upon. For example, first the sensor device can be subjected to a pulse pause, for example with a fixed time duration of 185 με. Subsequently, the sensor device can be acted upon with a further switching state, for example with a negative current pulse. Then again, the

Sensor device are applied with a further pulse pause. The duration of the pulse pause can be variable and, for example, be between 0 and 301 με. After the pulse pause, the sensor device can be subjected to a further switching state, for example with a positive current pulse. A duration of a switching state with a positive or a negative current pulse can be variable. For example, the duration can be between 90 and 391 με. Any change in the switching state can cause a charge reversal voltage swing at the suppression capacitors. The amount of charge per Umladehub can be a difference of

Voltages at the suppression capacitors between two switching states can be determined. In each case, a voltage at the end of a switching state for

Determination of the difference can be used. A charge amount dQ per _sx

Switching state change can be made from the voltage difference dUsx between two

Switching states are determined multiplied with a respective capacitance value of the interference suppression capacitance c _n: dQ = c _sx _n -dUsx. The average _{charge current} l _umsx one Switching state change may from l _to sx = _sx dQ / T _cyC | _{US be} determined. If now all transhipment, whose current flows through the sensor element added, the total Umladestrom l _pum can be _determined by the sensor element. This charge-reversal current can be taken into account in the calculation of the probe current; in particular, a correction of the probe current can take place. For example, in the pulsed operation, the sensor element with different current pulse patterns (timing mode) can be applied, for example with a pulse counter-pulse current pulse pattern (timing mode 1) or with a current pulse patterns with only negative pulses (timing mode 2). In the timing mode 1, a correction formula for the recharging current

lpum = [d (U _i2 -U _ref ) + c _a (U _a2 _-U _ref _{-U p0} )] / T _cydus , where U _{ref is} the reference value of the reference voltage of the sensor device and U _{p0 is} the value of the pump voltage in the pulse pause , U _i2 and U _a2 are voltage values at the end of a switching state, for example, a switching state with a negative

Current pulse, wherein the voltage U _a2 between the outer electrode and a mass can be measured and the voltage U _i2 between the inner electrode and the mass can be measured. Next are c, and c _a capacity values of

Entstörkapazitäten. In the timing mode 2, a correction formula for the charge-reversal current lpum = [d (U _i2 + U _i4 -2 _-U _re f) -2 c _a (U _a2 + U _ref + U _p0 )] / T _cydus , where U _i4 a voltage value at the end of a switching state is, for example, a switching state with a positive current pulse. To determine the

Correction formulas can basically be used for the capacitance values of the suppression capacities.

Such known methods for calibration, in particular the characteristic calibration, are dependent on capacitance values of the interference suppression capacities. In principle, nominal values of the components can be used for these capacitance values. However, this does not take account of specimen scatters, a possible temperature gradient and also not a possible long-term drift of the capacitance values. For applications, however, a pumping current accuracy of less than ± 10 μΑ may be required. For capacitance tolerances of up to ± 30% at λ = 1, calibration can be performed by means of the setpoint values of the

Suppressor capacitances lead to pumping current inaccuracies. Thus, overshoots can occur in a voltage curve, in particular in the voltage curve of a pumping voltage, which can not be acceptable for applications. Disclosure of the invention Therefore, a method is proposed for operating a sensor device which at least largely avoids the expected disadvantages of known methods. In particular, a pumping current accuracy of less than ± 10 μΑ should be achieved. In principle, a sensor device can be understood as any device which is set up to detect a proportion of a gas component, in particular in a gas mixture, for example in a measuring gas space such as, for example, an exhaust gas tract of an internal combustion engine. The sensor device has at least one sensor element for detecting at least a portion of one

Gas component in a gas in a sample gas chamber. A sensor element for detecting at least a portion of a gas component in a gas may be understood to be an element which, for example, is part of a

Sensor device, is set up or can contribute to a share of

Gas component of a gas to detect. With regard to possible embodiments of the sensor element, reference may in principle be made to the above-mentioned prior art. The sensor element may in particular be a ceramic

Be sensor element, in particular a ceramic sensor element with a

Layer structure. In particular, the sensor element can be a planar ceramic

Be sensor element. Under a collection of at least a portion of a

Gas component can be a qualitative and / or quantitative detection of a

Gas component of the gas to be understood. In principle, however, the sensor element can be set up to detect any physical and / or chemical property of the gas, for example a temperature and / or a pressure of the gas and / or particles in the gas. Other properties are basically detectable. The gas can basically be any gas, for example exhaust gas, air, an air-fuel mixture or even another gas. The invention can be used in particular in the field of motor vehicle technology, so that the gas can be, in particular, an air-fuel mixture. In general, a measuring gas space can be understood as meaning a space in which the gas to be detected is located. The

As stated above, the invention can be used in particular in the field of motor vehicle technology, so that the measuring gas chamber can be, in particular, an exhaust gas tract of an internal combustion engine. However, other applications are conceivable. The sensor element comprises at least a first electrode and at least one second electrode. The term "first" and "second" electrode are considered pure Designations used and in particular give no information about a

Order and / or about whether, for example, more electrodes are available. Under an electrode may generally be an electrically conductive region of the

Sensor element can be understood, which can be acted upon, for example, with electricity or voltage. The first and the second electrode may in particular be designed as metal-ceramic electrodes, that is to say as so-called cermet electrodes, in particular as platinum cermet electrodes.

The second electrode is arranged in at least one measuring cavity. A measuring cavity can be understood as a cavity within the sensor element which can be set up to receive a supply of a gas component of the gas. The measuring cavity can be configured completely or partially open. Furthermore, the measuring cavity can be completely or partially filled, for example with a porous medium, for example with porous alumina. For example, the second electrode may be configured as an inner pumping electrode.

The measuring cavity is at least one diffusion barrier with gas from the

Sample gas space acted upon. A diffusion barrier can be understood as meaning a layer of a material which promotes or enables a diffusion of a gas and / or fluid and / or ions, but suppresses a flow of the gas and / or fluid. In particular, the diffusion barrier may have a porous ceramic structure, in particular a porous ceramic structure with specifically set pore radii. The diffusion barrier may have a diffusion resistance, wherein the diffusion resistance is to be understood as the resistance which the diffusion barrier opposes to a diffusion flow.

The first electrode and the second electrode are connected via at least one solid electrolyte and form a pumping cell. A solid electrolyte may in particular be a ceramic solid electrolyte, for example zirconium dioxide, in particular yttrium-stabilized zirconium dioxide (YSZ) and / or scandium-doped zirconium dioxide (ScSZ). The solid electrolyte may preferably be gas-impermeable and / or may ensure ionic transport, for example ionic oxygen transport. In particular, the first and the second electrode can be an electrically conductive region, for example an electrically conductive metallic coating, which can be applied to the at least one solid electrolyte and / or in another way Can contact solid electrolyte. In particular, by applying a voltage, in particular a pumping voltage, to the first and second electrodes, oxygen can be pumped in or out of the gas into the measuring cavity through the diffusion barrier.

The sensor device furthermore has at least one controller. A control can be understood as a device that is set up

To operate sensor element. The control can be central or decentralized. The

Control may comprise at least one data processing device,

For example, at least one processor, in particular at least one

Microcontroller. The controller may for example be wholly or partially integrated into another device, for example in a control unit and / or in a

Engine control unit. The sensor element may have at least one interface which can be connected to the controller. For example, the controller may also be completely or partially integrated into the sensor element or, alternatively, be integrated in whole or in part in other components of the sensor arrangement, for example in a plug.

The controller is connected to the first electrode via at least one first signal line. In principle, a first signal line can be understood to mean any connection of the controller and the first electrode which is set up, at least one signal, in particular a current signal and / or a voltage signal, from the controller to the first electrode and / or from the first electrode to Transfer control. For example, the first signal line may be wholly or partly designed as a supply line and / or a cable and / or a switch. Supply line can be realized, for example, wholly or partly as a supply line in a layer structure.

The controller is connected to the second electrode via at least one second signal line. Under a second signal line can basically any

Connection of the control and the second electrode are understood, which is adapted to transmit at least one signal, in particular a current signal and / or a voltage signal, from the controller to the second electrode and / or from the second electrode to the controller. For example, the second signal line may also be configured entirely or partially as a supply line and / or as a cable and / or switch. The first signal line is connected to an electrical ground via at least one first interference suppression capacitance c1. The second signal line is connected to the electrical ground via at least one second interference suppression capacitance c2. Under an electrical ground can basically be understood an electrically conductive component having a reference potential, in particular a potential of 0 volts. The designation as "first" and as "second" suppression capacity is used as a pure name and in particular gives no information about an order and / or whether, for example, further suppression capacities are available. Under the first and the second

Noise suppression capacity can basically be understood as meaning any electrical capacitors which are set up to dampen radio frequency interference and high voltage inputs, in particular to conduct radio frequency interference and high voltage inputs against the electrical ground and thus to ensure protection, for example against static charges. Between at least one of the first signal line and the second signal line and the electrical ground is further arranged at least one measuring resistor. Under a measuring resistor can in principle be understood any ohmic resistance at which a current and / or voltage measurement can be performed. The first signal line and / or the second signal line can be connected to the electrical ground via the measuring resistor. Preferably, at least one switch can be provided in a connection comprising the measuring resistor between the first and / or the second signal line and the electrical ground. A switch can be understood to mean any component, in particular an electrically conductive component, which is set up with the first and / or second signal line

To connect measuring resistor and the electrical ground, in particular electrically, and / or a compound of the first and / or second signal line with the

Separate measuring resistor and the electrical ground. For example, in a closed state, the switch can connect the first and / or second signal line to the measuring resistor and the electrical ground and, in an open state, disconnect the first and / or second signal line from the measuring resistor and the electrical ground.

The measuring resistor and the second suppression capacitance c2 can be connected in parallel. In particular, the same pole of the measuring resistor and the second

Suppressor capacity c2 be interconnected. The measuring resistor and the first suppression capacitance c1 can be connected in parallel. The controller is set up to operate the pump cell with a functional current. In principle, a functional current can be understood to mean any current which, in principle, can have any desired profile. Preferably, the

Function stream comprise at least one current pulse, more preferably, the functional stream having a pulsed periodic profile. For example, the functional current can be selected from the group consisting of: a sinusoidal functional current, a rectangular current, a triangular current, a sawtooth current. In principle, the functional flow can also have a different course. In principle, "operating the pump cell with a functional current" can be understood as meaning that the controller can be set up to apply the functional current to the pump cell, in particular the first and / or the second electrode The functional current can furthermore have at least one pulse pause, wherein in a pulse pause the pump cell is not acted upon by a current pulse.

In the method, by applying the pumping cell with several different switching states, the first suppression capacity c1 and the second

Suppressor capacity c2 determined. In particular, the controller may include switches, preferably, the controller may include a plurality of switches. As a first switch, the switch described above may be provided in a connection between the second signal line and the electrical ground comprising the measuring resistor.

Furthermore, a second switch may be provided in a connection between the sensor element and a reference voltage source described in more detail below. A switching state can in principle by a state of the electronic components, in particular a state of at least two switches, and / or by a

Flow direction of the pumping current can be defined. Under a determination of the first interference suppression capacity c1 and the second interference suppression capacity c2 can basically a

Determining the capacitance values in an operation of the sensor device, in particular a determination of deviations from the desired value of the Entstörkapazitäten be understood.

In a further operation of the sensor device, in particular in a pulsed operation with a pulsed impingement of the pumping cell with current and / or voltage, the suppression capacitances can be taken into account. In particular, in the further operation of the sensor device can be corrected by the suppression capacitors caused overshoot. The first and the second suppression capacity can be reloaded in a pulsed operation of the probe depending on an application with a positive or a negative pulse. Such transhipment can lead to an additional current, in particular a recharging current, which can increase or decrease the pumping current. Such changes in the pumping current can too

Overshoot in the voltage curve of a pump voltage of the sensor element lead.

Furthermore, the suppression capacitances can be taken into account when determining a characteristic curve of the sensor device. A characteristic curve of the sensor device can be understood as meaning a dependence of the pumping voltage on the air ratio λ.

In particular, changes in the pumping current due to the recharging current and the resulting overshoots in the voltage curve can be taken into account when determining a characteristic curve of the sensor device.

The method may include the following steps:

a) a first measuring step, wherein in the first measuring step, the pumping cell with a first switching state, z ₀ , is applied, wherein in the first measuring step, a pumping voltage U _{p0 is} detected and a first voltage U _g o is determined at the measuring resistor, wherein in the first measuring step further a voltage Uc _a o between the first electrode and the electrical ground and a voltage Uc _i0 between the second electrode and the electrical ground is determined;

b) a second measuring step, wherein in the second measuring step, the pumping cell with a second switching state, z ₂ , is applied, wherein in the second

Measuring step, a voltage Uc _a 2 between the first electrode and the measuring resistor and a voltage Uc _i2 between the second electrode and the measuring resistor is determined, wherein further in the second switching state, a voltage U _{gua is} detected at the measuring resistor and a charge amount Q _{gua of} the charging current is determined from an overshoot; and

c) a third measuring step, wherein in the third measuring step, the pumping cell with a third switching state, z _1; is applied, wherein in the third measuring step, a voltage Uc _a1 between the first electrode and the measuring resistor and a voltage Uc _M between the second electrode and the measuring resistor is determined, and wherein a voltage U _gui on the Measuring resistance is detected and a charge amount Q _gU i of the charging current is determined from an overshoot.

The method steps can be carried out, for example, in the order mentioned. But also a different order is possible. In principle, one or more or all process steps can also be carried out repeatedly. The terms "first measuring step", "second measuring step" and "third measuring step" are used as a pure name and in particular give no information about an order and / or whether, for example, further measuring steps are available.

In the first measuring step, the pumping voltage U _p0 can be _detected at one end of a pulse pause of the functional _current . An end of a pulse pause can be understood as meaning a time within a pulse pause before a new pause

Action is taken with a current pulse. In the first switching state, the sensor element can be charged with a reference voltage. The first

Switching state can be understood as a currentless state, in particular a state of a pulse break, in which the pumping cell is not acted upon by a current pulse. In particular, in the first switching state, the second switch may have a closed state and thus the sensor element with a

Apply reference voltage. The reference voltage in the pulse pause can basically be chosen so that the voltage is greater than the largest possible negative polarization of the pumping cell. Thus, it can be prevented that a potential of the first electrode falls below the potential of the electrical ground. In particular, the reference voltage may be greater than 2V. Preferably, the reference voltage can be 3.3V. In particular, the sensor device may comprise an analog-to-digital converter having a reference voltage of 3.3V. At a

Voltage determination can be voltages between other elements of the

Referencing the sensor device to this reference voltage. The voltage Uc _i0 between the second electrode and the electrical ground may be equal to

Be reference voltage. The voltage Uc _a o between the first electrode and the electrical ground may be the sum of the reference voltage and the pumping voltage U _p0 . The voltage Uc _a 2 and the voltage Uc _i2 can be determined after a transient process. The voltage Uc _a i and the voltage Ucn can after a Transient process can be determined. Under a transient process may be a period of time until reaching a pump voltage value, which a

Deviation less than 20% of a steady state value of the pumping voltage, preferably a deviation of less than 15% and particularly preferably a deviation of less than 10% of a steady state value of the pumping voltage, be understood. Basically, a voltage determination without a

Transient occur.

For an exact determination of the voltages, a final state of the first switching state would basically have to be measured. As a rule, an accurate measurement of the final state can not be done. Preferably, in the method an averaging of

Voltage values take place, for example an averaging over 70με. The resulting detection error may be due to a depolarization movement of the

Suspend pump voltage during the pause. A measuring cycle can be understood as meaning a period in which at least one of the method steps a) -c) can be carried out. The method steps a) -c) can all be carried out within one measuring cycle or can be carried out individually in each case in one measuring cycle. A measuring cycle 666 may preferably be long. In the second switching state, the first electrode may be connected to the measuring resistor. In particular, in one comprising the measuring resistor

Connection between the first signal line and the electrical ground to be provided at least one switch which allows in the second switching state, a connection of the first electrode and the measuring resistor. In the second switching state, the sensor element can be subjected to a negative current pulse, so that the pumping current flows from the second electrode to the first electrode. In the second switching state, the pump cell can be acted upon by a current pulse of the functional current, in particular a negative pulse, and wherein the

Suppressor capacities are reloaded. A positive pulse can be understood to mean a pulse in which the current flows from the first electrode to the second electrode and via a switch to the measuring resistor. In contrast, in the case of a negative pulse, the current flows from the second electrode to the first electrode and via a switch to the measuring resistor. A recharge of Entstörkapazitäten can in particular take place when switching between different switching states. Preferably, a switching between the the first switching state and the second switching state, the second and the first switching state, the first and the third switching state and the third and the first switching state. In the third switching state, the second electrode may be connected to the measuring resistor. In particular, the first switch may be closed and a

Ensure connection of the second electrode and the measuring resistor. In the third switching state, the sensor element can be acted upon by a positive current pulse so that the pumping current flows from the first electrode to the second electrode. In the third switching state, the pumping cell with a current pulse of the

Function current, in particular a positive pulse, are applied, and the Entstörkapazitäten can be reloaded.

As stated above, a charge amount Q _{gua of} the charge- _{reversal current} can be determined from overshoot. In particular, an area under a time course of an overshoot may be proportional to the charge amount of the charge-reversal current. The voltage U _gua can be determined by integrating a voltage signal over a pulse duration. In particular, the voltage U _{gua can be} determined by integration over an integration time of at most 100 με, preferably of at most 80 με and particularly preferably of about 71 με, for example 70 ± 5 με. In a preferred embodiment, the integration time may be 71 με. Also, an integration time which is longer than 71 με, may be possible in principle. The

Sensor device may comprise a sigma-delta converter. The sigma-delta converter can be set up to integrate a voltage signal detected at the measuring resistor over a period of time, in particular over the integration time. Preferably, the integration can take place starting with the application of a switch-on edge. A switch-on edge can be understood to mean a behavior of the pump voltage when the current pulse is acted upon. From the voltage U _gua thus determined, that can

Voltage signal to be subtracted without overshoot. In particular, the voltage U _g0 determined in the first switching state can be subtracted from the voltage U _gua , wherein the functional current can have the same value in the voltage measurement in the first and the second switching state. The sensor device may comprise at least one power source, which may be arranged at all

Measurements in the different switching states to feed the same power. In particular, the current source can be a constant current source. Especially

Deviations such as a voltage transition of the at least one power source can Generate measurement errors. The difference of the voltages U _g0 and Ug _Ua can be proportional to the charge amount of the charge- _reversal current. In particular, the charge amount Q may _{gu £} = (U _PDO a - U _G0) be -Tadc Rgnds wherein TADC is the conversion time of the sigma-delta converter and Rgnds the target value of the measuring resistor. In one embodiment, the conversion time may be 70με.

An analogous determination can be made with regard to the charge quantity Q _gui of the charge- _reversal current. In particular, the charge quantity can be Q _gui = (U _gU i _-U _g o) -T _ad c / R _gn ds.

The sensor device may be configured to perform a determination of the charge quantities Q _gu and Q _gua . The sensor device can be set up

Process step a) - c) perform. The sensor device can be set up to control a starting time for a measuring cycle and / or a change between the switching states, preferably to precisely control μ seconds. In a preferred embodiment of the sensor device, the sensor device may comprise a combination of an analog low-pass filter and a delta-sigma converter. In principle, other embodiments are conceivable. For example, an analog integrator could be used with its final value sampled and AD converted. These measured charge quantities Q _gua and Q _gU i of the charge transfer current can be compared with the expected charge quantities of the charge.

The method may further comprise the following steps:

i) a first determining step, wherein a difference dUc _{i2 of} the voltage Uc _i0 and the voltage Uc _i2 and a difference dUc _a 2 of the voltage Uc _a o and the voltage Uc _{a2 is} determined;

a second determining step wherein a difference dUc _{M of} the voltage Uc _i0 and the voltage Uc _M and a difference dUc _{a1 of} the voltage Uc _a0 and the voltage Uc _{a1 are} determined;

iü) a third determination step, wherein the suppression capacitances d and c _{2 are} determined.

The method steps can be carried out, for example, in the order mentioned. But also a different order is possible. In principle, one or more or all process steps can also be carried out repeatedly. The terms "first determining step", "second determining step" and "third determination step" are used as a pure name and in particular give no information about an order and / or about whether, for example, more determination steps are available. In the third determination step, the suppression capacitances d and c ₂ can be determined by solving a linear system of equations. In particular, the

Suppression capacitances by solving the equation system dLk Ci + dUC _a2 -C2 = Qgua dUC _ü -d + dUc _a1 -c ₂ = Q _{gui be} determined. In the case of large overshoots, a precise determination of the suppression capacity can be carried out. An exact determination of the suppression capacitances can be made if the surface of the Umladevorgangs the suppression capacitors, so the area under the overshoot is so large that tolerances of the switching times have the least possible impact on the result and the transshipment is not longer than the integration time. Basically, it is known from the prior art that

To operate sensor element with a current of 16 mA, wherein the measuring resistor is 100 Ω. In the context of the present invention, it has proved to be advantageous to operate the sensor element with as small a current as possible. By way of example, a current which is as small as possible can be understood as meaning a current of less than 16 mA, preferably less than 12.5 mA, and particularly preferably of 10 mA. Other currents are possible. By way of example, the sensor device can have an adjustable current source, which makes it possible to regulate the current for operating the sensor element and thus enables an adjustment. In a preferred embodiment, the sensor element can be operated with a current of 10 mA. Other currents are possible. The measuring resistor can in this

For example, the preferred embodiment may have a resistance of 100 Ω, and a resistance of the sensor element may be 26 Ω, for example. However, other resistances are possible. When determining the suppression capacitances, the voltage U _{ci (1/2),} for example, from 3.3 V to 1, 26 V are reloaded. Other voltages are possible. In order to ensure that a measurement of the pump voltage is possible even when the current is reduced to 10 mA, a duration of the pulse pause before the positive pulse, in particular before the third

Switching state, be chosen so that a pump voltage measurement performed can be. Preferably, the sensor element can be operated in a λ = 1 control mode in which a pumping current requirement can be low. Thus, it can be prevented that a duration of the pulse pause in comparison to the entire measurement cycle is not too large. In particular, the duration of the pulse pause may amount to 15%, preferably 10% and particularly preferably 5%, of the measurement cycle. Further preferably, the pump voltage over several switching cycles, the pump voltage make no changes, since the voltage values to be detected can be distributed over several cycles over time.

In principle, however, changes in the range of 10%, preferably 5% and particularly preferably 1% of the pumping voltage may be possible. The pumping voltage can be particularly stable after a λ = 1 passage and less stable during the λ = 1 passage. Under a switching cycle can be a change between

at least one switching state selected from the first, second and the third switching state and a further switching state selected from the first, second and the third switching state to be understood.

As described above, the sensor device may comprise a sigma-delta converter, the method having a non-linearity correction.

In principle, real sigma-delta converters can not reproduce non-linear signals linearly but only distorted compared to an ideal sigma-delta converter signal, so that a nonlinearity correction of the voltage values may be necessary. The non-linearity correction can be carried out with a correction function, which can depend on the interference suppression capacities. The correction function can be performed by comparing a real sigma-delta converter with a simulated, ideal sigma-delta converter. To a mode of operation of the sigma-delta converter also during the

Therefore, a recursive determination of the suppression capacity can be carried out to ensure the determination of the suppression capacity. In particular, in a first

Correction step, a determination of uncorrected interference suppression capacities with an uncorrected sigma-delta converter signal and a nonlinearity correction with the non-corrected interference suppression capacitances are performed. In a further correction step, corrected differences of the voltage _values (U _gui - U _g0 ) and (U _gua - U _g o) can be determined and a determination of corrected interference suppression capacities can be made. In particular, these correction steps can be carried out individually or both repeatedly to achieve a desired accuracy of the nonlinearity correction. In a further aspect of the present invention, a sensor device is proposed. The sensor device has at least one sensor element for

Detecting at least a portion of a gas component in a gas in a sample gas space. The sensor element comprises at least one first electrode and at least one second electrode, wherein the second electrode is arranged in at least one measuring cavity. The measuring cavity is over at least one

Diffusion barrier acted upon with gas from the sample gas space. The first electrode and the second electrode are connected via at least one solid electrolyte and form a pumping cell. The sensor device furthermore has at least one controller, which is connected to the first electrode via at least one first signal line. The controller is connected to the second electrode via at least one second signal line. The first signal line is connected to an electrical ground via at least one first interference suppression capacitance c1. The second signal line is connected to the electrical ground via at least one second interference suppression capacitance c2. At least one measuring resistor is arranged between the electrical ground and at least one of the first signal line and the second signal line. The controller is set up to operate the pump cell with a functional stream.

The sensor device is set up to carry out a method according to one of the embodiments mentioned above or below.

For example, the controller may be set up to perform the method, for example programmatically. For possible embodiments of the sensor device, reference may accordingly be made to the above description of the method.

The invention further relates to computer programs which are adapted to perform each step of the inventive method, electronic storage medium on which such a computer program is stored and electronic

Control devices comprising such an electronic storage medium.

Advantages of the invention

The method described is advantageous over known methods of the prior art. In particular, actual values of suppression capacitances can be determined and thus specimen scatters, temperature response and long term drifts of

Suppressor capacities are taken into account in a characteristic calibration. Furthermore, can such use of the sensor device also for applications in which

Pump current accuracies of less than ± 10μΑ may be necessary to be possible.

Brief description of the drawings

Show it:

Figure 1 A - 1 C: an equivalent circuit diagram of a sensor device in three switching states for

Implementation of a method according to the invention;

FIG. 2 shows a schematic overview of a determination of a charge-reversal current;

Figure 3A - 3C: time course of a pumping current, voltage waveform across a first and second electrode and the course of a voltage difference of

Voltages of the first and second electrodes.

Embodiments of the invention

FIGS. 1A-1C show an equivalent circuit diagram of a sensor device 110 in three switching states for carrying out a method according to the invention. The sensor arrangement 1 10 has at least one sensor element 1 12 for detecting at least a portion of a gas component in a gas in a measuring gas chamber 1 14. The measuring gas chamber 14 may in particular be an exhaust gas tract of an internal combustion engine and the gas may be an exhaust gas. In particular, the sensor element 12 may be configured to determine a proportion of oxygen in the gas.

The sensor element 1 12 comprises at least a first electrode 1 16 and a second electrode 1 18. The first electrode 1 16 may, for example, as an outer

Pump electrode to be configured and is the equivalent circuit diagrams of Figures 1 A - 1 C marked as APE. The first electrode 1 18 can be acted upon with gas from the measuring gas chamber 1 14 and be connected, for example, with a gas-permeable layer with the measuring gas chamber 1 14. The second electrode 1 18 is arranged in at least one measuring cavity 120, which is not shown here. The measuring cavity 120 is connected to the measuring gas chamber 14 via at least one diffusion barrier 122. For example, the sensor element may have a gas inlet channel. Of the Measuring cavity 120 may be designed to be completely or partially open and may be constructed in several parts. For example, the measuring cavity 120 may be completely or partially filled, for example, with porous alumina. With regard to the configuration of the measuring cavity 120 and the diffusion barrier 122, in particular

Reference may be made to sensor elements of the prior art, which are described, for example, in Konrad Reif (Ed.) "Sensors in Motor Vehicles", 2nd Edition 2012, pages 160-165 The second electrode 1 18 may be designed as an internal pumping electrode the equivalent circuit diagrams of Figures 1 A - 1 C as IPE

characterized. The first electrode 1 16 and the second electrode 1 18 are connected via at least one solid electrolyte 124 (also not shown here), for example of yttrium-stabilized zirconia (YSZ) and / or scandium-doped zirconia (ScSZ). With regard to the configuration of the solid electrolyte 124, reference may also be made to the above-mentioned prior art. The first electrode 16 and the second electrode 118 form a pumping cell 126.

The sensor device 110 further has at least one controller 128. The controller 128 may be wholly or partially integrated into the sensor element 1 12, or alternatively be integrated in whole or in part in another component, for example in a plug and / or a motor control. The controller 128 is connected to the first electrode 1 16 via at least one first signal line 130. The controller 128 is connected via at least one second signal line 132 to the second electrode. The first signal line 130 is connected to an electrical ground 136 via at least one first interference suppression capacitance c1, identified by the reference numeral 134. The second signal line 132 is connected to the electrical ground 136 via at least one second interference suppression capacitance c2, identified by the reference numeral 138. Between at least one of the first signal line 130 and the second signal line 132 and the electrical ground 136, at least one measuring resistor 140 is furthermore arranged. The first signal line 130 and / or the second signal line 132 can via the

Measuring resistor 140 to be connected to the electrical ground 136. Preferably, in a connection comprising the measuring resistor 140 between the first

Signal line 130 and / or the second signal line 132 and the electrical ground 136 at least one switch 142 may be provided. The measuring resistor 140 and the

Suppression capacity c1 134, and / or the measuring resistor 140 and the suppression capacity c2 138 may be connected in parallel. The controller 128 may be configured to operate the pumping cell 126 with a functional current, in particular a pulsed square-wave current. In the method, by applying the pumping cell 128 with a plurality of different switching states, the first suppressing capacitance c1, 134, and the second suppressing capacitance c2, 138 are determined.

FIG. 1A shows a first switching state 144. The inventive method may include a first measuring step in which the pumping cell 126 is acted upon by the first switching state 144. The first switching state 144 may be a de-energized state; in particular, the pumping cell 126 may be acted upon by the first switching state 144 during a pulse pause of the functional current. In particular, the first electrode 1 16 can be acted upon by a current source 145. In the first measuring step, a pump voltage U _{p0 can be} detected and a first

Voltage U _{g0 be determined} on the measuring resistor 140. The arrow 146 indicates the direction of the pumping voltage U _p0 . The pumping voltage U _p0 can be detected at one end of a pumping pause of the functional current. In the first measuring step, furthermore, a voltage Uc _a o between the first electrode 1 16 and the electrical ground 136 and a voltage Uc _i0 between the second electrode 1 18 and the electrical ground 136 can be determined. In the first switching state 144, the sensor element 1 12, in particular the second electrode 1 18, are subjected to a reference voltage. In particular, the sensor device 1 10 a

Reference voltage source 148 which is adapted to pressurize the sensor element 1 12 with a reference voltage. In a preferred

For example, the reference voltage may be 3.3V.

Between the second signal line 132 and the reference voltage source 148, a switch 150 may be arranged, wherein in a closed state of the switch 150, the reference voltage source 148 and the sensor element 1 12 are connected. Arrow 152 indicates the direction of the pumping current.

FIG. 1B shows a second switching state 154. The method according to the invention can comprise a second measuring step in which the pumping cell 126 can be acted upon by the second switching state 154. In the second switching state 154, the pumping cell 126 can be acted upon by a current pulse of the functional current, in particular a negative pulse, with the first interference suppression capacitance c1 134 and the second interference suppression capacitance c2 138 being transferred. Furthermore, the first signal line 130 may be connected to the measuring resistor 140, wherein the switch 142 between the first signal line and the measuring resistor 140 may be closed. By doing second measuring step, a voltage Uc _a2 between the first electrode 1 16 and the measuring resistor 140 and a voltage Uc _i2 between the second electrode 1 18 and the measuring resistor 140 can be determined. The voltage Uc _a2 and the voltage Uc _i2 can be determined after a transient process. Furthermore, in the second switching state 154, a second voltage U _gua can be detected at the measuring resistor 140 and a charge quantity Q _{gua of} the recharging current can be detected from a

Overshoot will be determined.

The determination of the charge quantity Q _gua of the charge- _reversal current is shown schematically in FIG. In the left-hand column of FIG. 2, a possible time profile of the voltage across the measuring resistor is shown. This voltage signal can

include at least two signal components. This composition of the

Voltage signal is shown in the middle column of Figure 2. A first

Signal component 156 may be a function, such as here a

Rectangular function, the function current to be the following voltage signal of the voltage U _g0 , which is shown in the middle column of Figure 2 as a thick solid line. A second signal component 158 may be the overshoot caused by a recharge of the suppression capacitors 134, 138. The second

Signal component 158 is shown in the middle column of Figure 2 as a thin solid line. The voltage U _gua can be determined by integration of the voltage signal over a pulse duration. In particular, the voltage U _gua through

Integration over an integration time are determined, which corresponds for example to a minimum pulse duration of a current pulse. The pulse duration of a current pulse may be, for example, 90 με to 391 με. However, other pulse durations are possible in principle. For example, the integration time 71, 04 με amount. The sensor device 110 may comprise a sigma-delta converter. The sigma-delta converter may be configured to supply the voltage signal over a period of time,

especially over the integration time. Preferably, the integration can take place starting with the application of a switch-on edge. From the voltage U _gua thus determined, the voltage signal without overshoot, in particular the first signal component, can be subtracted. The difference 160 of the voltages U _g0 and U _gua is shown in the left-hand column of FIG. 2 as a thick dashed line and may be proportional to the charge quantity Q _gua of the charge- _{reversal current} . FIG. 1C shows a third switching state 162. The inventive method may include a third measuring step, in which the pumping cell 126 with the third Switching state 162 is applied. In the third switching state 162, the

Pumping cell 126 with a current pulse of the functional current, in particular a positive pulse, are applied and the Entstörkapazitäten 134, 138 are reloaded. In the third measuring step, a voltage Uc _a i between the first electrode 1 16 and the measuring resistor 140 and a voltage Uc _n between the second electrode 1 18 and the measuring resistor 140 can be determined. The voltage Uc _a i and the voltage Ucn can be determined after a transient process. Furthermore, a voltage U _gui on the measuring resistor 140 can be detected and a charge quantity Q _{gui of} the charge- _reversal current can be determined from an overshoot. A determination of the charge quantity Q _gui can analogously to the determination outlined in FIG

Amount of charge Q _gua the Umladestroms done.

Switching between the various switching states can occur, in particular, between the first switching state 144 and the second switching state 154, the second switching state 154 and the first switching state 144, the first switching state 144 and the third switching state 154 and the third switching state 162 and the first switching state 144. Furthermore, the method can be a first

Determining step, wherein a difference dUc _{i2 of} the voltage Uc _i0 and the voltage Uc _i2 and a difference dUc _a 2 of the voltage Uc _a0 and the voltage Uc _{a2 is} determined. The method may include a second determining step wherein a difference dUc _{M of} the voltage Uc _i0 and the voltage Ucn and a difference dUc _a i of the voltage Uc _a0 and the voltage Uc _a i is determined. Furthermore, the method may have a third determination step, wherein the suppression capacitances d and c _{2 are} determined. In the third determination step, the suppression capacitances d 134 and c ₂ 138 can be determined by solving a linear system of equations.

FIG. 3A shows the time profile of the pumping current with which the sensor element 12 can be acted upon. The sensor element 1 12 can be operated in pulse mode, in which in this embodiment, the pumping cell 126 is acted upon by a pulsed current. Thus, in the course of time, positive and negative current pulses of the functional current, in this case a square-wave current, can be recognized in FIG. 3A. FIG. 3C shows the profile of a voltage difference AU between the first electrode 16 and the second electrode 118. Both the pump current in FIG. 3A and the voltage difference in FIG. 3C show overshoots, deviations from the rectangular function, due to charge-reversal currents of the suppressor capacitors 134, 138. FIG. 3C illustrates the time profile of the voltages U _x determined in the method according to the invention. The curve 164 shows the profile of the voltage at the

Measuring resistor 140 falling voltage. The curve 166 or the curve 168 shows the profile of the voltage between the electrical ground 136 and the first electrode 1 16 and the second electrode 1 18. At time tO, the sensor element 1 12 can be acted upon by the first switching state 144. The voltage Uc _i0 between the second electrode 1 18 and the electrical ground 136 is denoted by the reference numeral 170 and the voltage Uc _a o between the first electrode 16 and the electrical ground 136 is designated by the reference numeral 172. At time t1, the sensor element 1 12 can be acted upon by the second switching state 154. The voltage Uc _a2 between the first electrode 1 16 and the measuring resistor 140 is denoted by the reference numeral 174 and the voltage Uc _i2 between the second electrode 1 18 and the measuring resistor 140 is designated by the reference numeral 176. At time t2, the sensor element 1 12 can be repeatedly applied to the first switching state 144. Further, at the time t3, the sensor element 1 12 can be acted upon by the third switching state 162. The voltage Uc _a i between the first electrode 1 16 and the measuring resistor 140 is denoted by the reference numeral 178 and the voltage Uc _n between the second electrode 1 18 and the measuring resistor 140 is designated by the reference numeral 180. In a further operation of the sensor device 1 10, in particular in a

Pulsed operation with a pulsed loading of the pumping cell 126 with current and / or voltage, the suppression capacitors 134, 138 can be considered and

be corrected in particular by Umladeströme overshoots caused. Furthermore, the interference suppression capacitors 134, 138 can be taken into account when determining a characteristic curve of the sensor device 1 10.

Claims

Method for operating a sensor device (1 10), wherein the sensor device (1 10) has at least one sensor element (1 12) for detecting at least a portion of a gas component in a gas in a measurement gas space (1 14), wherein the sensor element (1 12) at least one first electrode (1 16) and at least one second electrode (1 18), wherein the second electrode (1 18) is arranged in at least one measuring cavity (120), wherein the measuring cavity (120) via at least one diffusion barrier (122) with gas from the measuring gas space (1 14) can be acted upon, wherein the first electrode (1 16) and the second electrode (1 18) via at least one solid electrolyte (124) are connected and form a pumping cell (126), wherein the sensor device (1 10) at least one

Control (128), wherein the controller (128) via at least a first signal line (130) to the first electrode (1 16) is connected, wherein the

Control (128) via at least one second signal line (132) to the second electrode (1 18) is connected, wherein the first signal line (130) via at least one first Entstörkapazität c1 (134) is connected to an electrical ground (136) the second signal line (132) via at least one second

Entstörkapazität c2 (138) is connected to the electrical ground (136), wherein between the electrical ground (136) and at least one of the first

Signal line (130) and the second signal line (132) at least one

Measuring resistor (140) is arranged, wherein the controller (128) is adapted to operate the pumping cell (126) with a functional current, wherein in the method by applying the pumping cell (126) with a plurality of different

Switching states, the first suppression capacity c1 (134) and the second suppression capacity c2 (138) are determined.

Method according to the preceding claim, wherein in a further operation of the sensor device (1 10), in particular in a pulsed operation with a pulsed loading of the pumping cell (126) with current and / or voltage, the suppression capacitances are taken into account.

Method according to the preceding claim, wherein in the further operation of the sensor device (1 10) by the suppression capacitors (134, 138) caused overshoots are corrected. Method according to one of the preceding claims, wherein in a determination of a characteristic of the sensor device (1 10) the suppression capacitances (134, 138) are taken into account.

Method according to one of the preceding claims, wherein the method comprises the following steps:

iii) a first measuring step, wherein in the first measuring step the pumping cell

(126) is acted upon with a first switching state (144), wherein in the first measuring step, a pumping voltage U _{p0 is} detected and a first voltage U _{g0 is determined} at the measuring resistor (140), wherein in the first measuring step further comprises a voltage Uc _a o between the first

Electrode (1 16) and the electrical ground (136) and a voltage Uc _i0 between the second electrode (1 18) and the electrical ground (136) is determined;

iv) a second measuring step, wherein in the second measuring step, the pump cell (126) is acted upon by a second switching state (154), wherein in the second measuring step, a voltage Uc _a2 between the first electrode (1 16) and the measuring resistor (140) and a voltage Uc _i2 between the second electrode (1 18) and the measuring resistor (140) is determined, wherein further in the second switching state (154) a second voltage U _gua on the measuring resistor (140) is detected and a charge amount Q _{gua of} the charge- _reversal can be determined from an overshoot; and v) a third measuring step, wherein in the third measuring step the pumping cell

(126) is acted upon by a third switching state (162), wherein in the third measuring step, a voltage Uc _a1 between the first electrode (1 16) and the measuring resistor (140) and a voltage Ucn between the second electrode (1 18) and the Measuring resistor (140) is determined, and wherein a voltage U _gui on the measuring resistor (140) can be detected and a charge amount Q _{gui of} a recharging current is determined from an overshoot.

Method according to the preceding claim, wherein in the second

Switching state (154) the pumping cell (126) with a current pulse of the

Function current, in particular a negative pulse, is applied, and wherein the Entstörkapazitäten (134, 138) are reloaded. Method according to one of the two preceding claims, wherein in the third switching state (162), the pumping cell (126) with a current pulse of the

Function current, in particular a positive pulse, is applied and wherein the Entstörkapazitäten (134, 138) are reloaded.

Method according to one of the three preceding claims, wherein the method further comprises the following steps:

iv) a first determining step wherein a difference dUc _{i2 of} the voltage UCio and the voltage Uc _i2 and a difference dUc _{a2 of} the voltage Uc _a0 and the voltage Uc _{a2 is} determined;

v) a second determination step wherein a difference dllcn of the voltage UCio and the voltage Uc _n and a difference dUc _a i of the voltage Uc _a0 and the voltage Uc _{a1 is} determined;

vi) a third determination step, wherein the suppression capacitances d (134) and c ₂ (138) are determined.

Method according to the preceding claim, wherein in the third

Determination step by solving a linear system of equations

Suppression capacitances d (134) and c ₂ (138) are determined.

Method according to one of the preceding claims, wherein the sensor device (1 10) comprises a sigma-delta converter, the method having a

Non-linearity correction. 1 1. A computer program arranged to perform each step of the method of any one of the preceding claims.

12. An electronic storage medium on which a computer program according to the preceding claim is stored.

13. An electronic control unit comprising an electronic storage medium according to the preceding claim.