Volume IV, Edition 3
The Thermo Scientific™ Model 42i NO-NO2-NOx Analyzer utilizes chemiluminescence technology to measure the amount of nitrogen oxides in the air from sub-ppb levels up to 100ppm. In the event you are unable to calibrate your Model 42i NO-NO2-NOx analyzer with zero air or nitrogen and receive a background “above or below limit” error, this month’s Fast5 tip can help.
Isolate and determine where the elevated background/zero is originating
You need to isolate and determine where the elevated background/zero is coming from as it could be external contamination in your zero air or your sample line/umbilical. The elevated background could also be electronic noise from the PMT (Photomultiplier Tube) or your input board may require calibration. See the Model 42i NO-NO2-NOx Analyzer
Troubleshooting High/Low background errors technical bulletin.
This procedure will have you isolate the following items:
- Isolate external contamination
Disconnect sample line and see if concentrations drop.
- Isolate internal contamination
If you disconnect the sample line and the NO/NOx Concentrations stays high this could be internal Contamination and the reaction chamber may need cleaning.
- Measure and determine the electronic noise level
Measure the dark current/noise from the PMT, should be a very low level.
- Calibrate input board for any offsets
Perform an automatic input board calibration from the service menu.
- Clean your reaction chamber if contaminated
If this process determines your Model 42i NO-NO2-NOx Analyzer is contaminated, use this cleaning procedure to clean your reaction chamber, you may also need to replace some Teflon tubing inside the analyzer as well, depending on the contamination level. See the Model 42i NO-NO2-NOx Analyzer Reaction Chamber Cleaning Procedure technical bulletin.