NOx is a general term pertaining to oxides of nitrogen, the most common being nitric oxide (NO) and nitrogen dioxide (NO2).

Nitrogen oxides are typically created in the combustion process when burning fuels at high temperatures.

Below are worked examples of a NOx calculation.

NOx CALCULATIONS for the KM9106

ONLY an NO Sensor fitted:

Working in ppm NOx referenced to NO

The user can select the assumed NO2 percentage and the O2 normalised level.

Then:      NOx in ppm = NO in ppm multiplied by (1 + assumed NO2 percentage)

In this setup NOx can only be displayed as NOx = NO

Then normalising:

NO in ppmn = NO in ppm multiplied by (21 minus the O2norm setting) and then divided by (21 minus the actual O2 reading)

For a worked example assume:

NO is 1000ppm

NO2 is 5% of NO

O2norm is set to 3%

Actual O2 is zero

NOx in ppm = 1000 x (1+5/100) = 1000 x 1.05 = 1050 ppm

No ppm n = 1000 x (21-3)/(21-0) = 1000 x 18/21 = 857 ppm n

Nox ppm n = 1050 x 18/21 = 900 ppm n

Or

Nox ppm n = 857 x 1.05 = 900 ppm n

Working in mg/m3 NOx referenced to NO or No2

The user can select the assumed NO2 percentage, the O2 reference level and whether the NOx reading is referenced to NO or NO2.

Referenced to NO:

NO in mg/m3 = NO in ppm multiplied by 1.34

NOx in mg/m3 = NO in mg/m3 multiplied by (1 + assumed NO2 percentage)

NOx referenced to NO2:

NOx in mg/m3 = NO in ppm multiplied by 2.05 multiplied by (1 + assumed NO2 percentage)

or

NOx in mg/m3 - NO in mg/m3 divided by 1.34, multiplied by 2.05 and multiplied by (1 + assumed NO2 percentage)

Normalising readings:

Normalised reading = initial reading multiplied by (21 minus the O2norm setting) and then divided by (21 minus the actual O2 reading)

BOTH NO and NO2 sensors Fitted

Working in ppm         NOx = No = NO2

Normalised Readings:

Ppmn = initial reading in ppm mulitiplied by (21 minus the O2norm setting) and then divided by (21 minus the actual O2 reading)

Working in mg/m3:

The user can select hwo the readings are referenced.

NOx = SUM

NOx = NO

NOx = NO2

NOx = SUM:

NOx in mg/m3 = NO in ppm multiplied by 1.34 plus NO2 in ppm multiplied by 2.05

NOx = NO:

NOx in mg/m3 = (NO in ppm plus NO2 in ppm) multiplied by 1.34

NOx = NO2:

NOx in mg/m3 = (NO in ppm plus NO2 in ppm) mulitplied by 2.05

Normalising Readings:

Ppmn = initial reading in ppm multiplied by (21 minus the O2norm setting) and then divided by (21 minus the actual O2 reading)

Mg/m3n = initial reading in mg/m3 multiplied by (21 minus the O2norm setting) and then divivded by (21 minus the actual O2 reading)

ONLY an NO2 Sensor Fitted

When there us only an NO2 sensor fitted the NOx function is disabled.

NO2 in mg/m3 = NO2 in ppm multiplied by 2.05

Normalising Readings:

ppmn = initial reading in ppm multiplied by (21 minus the O2norm setting) and then divided by (21 minus the actual O2 reading)

mg/m3n = initla reading in mg/m3 multiplied by (21 minus the O2norm setting) and then divided by (21 minus the actual O2 reading)