Method and device for operating a nitrogen oxide sensor

1. A method for operating a nitrogen oxide sensor, the method comprising:

sensing a first measurement signal of the nitrogen oxide sensor, the first measurement signal representing a detected voltage between a reference electrode and an external electrode;

sensing a second measurement signal representing a measured gas content in a measuring chamber of the nitrogen oxide sensor;

comparing the first measurement signal with a predefined first threshold value; and

if the first threshold value is exceeded, assigning the second measurement signal to an emission of NH3.

2. The method as claimed in claim 1 , further comprising:

comparing the second measurement signal with a predefined second threshold value; and

if the second threshold value is undershot, assigning the second measurement signal to an emission of NOx if the first measurement signal undershoots the predefined first threshold value.

3. The method as claimed in claim 1 , wherein the method is carried out during a nitrogen oxide trap regeneration phase.

4. The method as claimed in claim 1 , wherein the predefined first threshold value is approximately 450 mV.

5. The method as claimed in claim 1 , wherein the predefined second threshold value is approximately 10 ppm.

6. A controller for a motor vehicle, the controller comprising:

a processing unit;

a data memory; and

a communication interface;

wherein the data memory stores a program for operating a nitrogen oxide sensor, wherein the processing unit executes the program comprising:

sensing a first measurement signal of the nitrogen oxide sensor, the first measurement signal representing a detected voltage between a reference electrode and an external electrode;

sensing a second measurement signal representing a measured gas content in a measuring chamber of the nitrogen oxide sensor;

comparing the first measurement signal with a predefined first threshold value; and

if the first threshold value is exceeded, assigning the second measurement signal to an emission of NH3.

7. A motor vehicle comprising:

an internal combustion engine including a combustion chamber;

an exhaust tract transporting fluids exhausted from the combustion chamber;

a nitrogen oxide sensor disposed in the exhaust tract; and

a controller programmed to:

sense a first measurement signal of the nitrogen oxide sensor, the first measurement signal representing a detected voltage between a reference electrode and an external electrode;

sense a second measurement signal representing a measured gas content in a measuring chamber of the nitrogen oxide sensor;

compare the first measurement signal with a predefined first threshold value; and

if the first threshold value is exceeded, assign the second measurement signal to an emission of NH3.