The gas electrode forms a part of the online cloud water chemistry analysis operated by the Centre for Ecology and Hydrology. The method involves mixing sample stream with dilute alkali (NaOH) which liberates NH3 gas, and the NH4+ ions are recorded by the electrode.
The files containing the data from this instrument may have suffix of .cno (for online ammonium ion analysis) and .cw2 (for batch ammonium ion analysis used when there is little cloud water for online analysis)