The readings from the connected NOX sensor are converted according to VDMA 6299:2019-09 in the NOX monitor of the EasyNOₓ.
At first, the oxygen content measured in wet exhaust gas is converted to dry exhaust gas:
In this context, the NOX monitor of the EasyNOₓ does not regard oxygen readings for wet exhaust gas, which lead to oxygen contents in the dry exhaust gas of over 20 %.
In the next step, the measured nitrogen oxide value is corrected by sensor- and plant-specific NO2 correction factors:
Following that, this NO2-corrected nitrogen oxide value measured in wet exhaust gas is converted to dry exhaust gas:
Then the volume-based nitrogen oxide measured value is converted to a mass-based value in mg/Nm3:
In the last step, the mass-based nitrogen oxide measured value is converted to a reference oxygen content of Or = 5 %:
Variable |
Meaning |
---|---|
K |
NO2/NOX ratio of the exhaust gas as a constant (see section Determining the NO2/ NOₓ Ratio) |
KNO2 |
Sensor-specific NO2 correction factor as a constant (see section Sensor) |
NOX,r |
Nitrogen oxide measured value converted to reference oxygen content and based on mass and dry exhaust gas in mg/Nm3 |
NOX,w |
Nitrogen oxide value of the NOX sensor measured wet in ppm |
NOX,w-c |
NO2-corrected nitrogen oxide measured value related to wet exhaust gas in ppm |
NOX,dr |
Nitrogen oxide measured value related to dry exhaust gas in ppm |
NOX,dr-mg |
Mass-based nitrogen oxide measured value related to dry exhaust gas in mg/Nm3 |
Or |
Reference oxygen |
O2,dr |
Oxygen measured value of the NOX sensor calculated on dry exhaust gas in vol.% |
O2,w |
Oxygen value of the NOX sensor measured wet in vol.% |