Many applications require a true NOx value which means to determine the NO resp. NO2 concentrations effectively present in the sampled gas. The following factors are of high importance for the NOx determination: quick transport thru the gas sampling system (with smaller diameter by highest pump performance), avoidance of condensate formation (provided by sampling tubing with PTFE sleeve and gas cooler) and in addition gas drying via gas cooler. With ecom instruments, NOx measurements can be performed with the following measurement principles offering different accuracy levels:
- Electrochemical measurement (NO and NO2 gas sensors)
- Chemiluminescence (CLD) for NO measurement in combination with an NO2 gas sensor (electrochemical measurement)
- Chemiluminescence (CLD) in connection with a converter which transforms NO2 into NO and enables to completely measure the nitrogen oxides content (NOx).
- Chemiluminescence (CLD) for the NO measurement in connection with photoacoustic spectroscopy (PAS) for the NO2 measurement