The Fixed Ion Strength method forms a part of the cloud water chemistry analysis method by the Centre for Ecology and Hydrology. The pH is measured with a micro-pH electrode at a fixed (high) ionic strength to provide fast electrode response through adding 1M KCl to the sample stream. The measurements were calibrated against dilute sulphuric acid solutions.
The files containing the data from this instrument may have suffix of .cph (for online pH analysis) and .cw2 (for batch pH analysis used when there is little cloud water for online analysis)