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I have experienced on a regular basis that
different pH meters, despite being properly calibrated, will produce
significantly different pH readings on the same solutions. This is
particularly common with lower quality electrodes because they respond to
other 'species' which are electrochemically similar to hydrogen ions, such
as sodium. For this reason a grower can get pH readings differing by more
than 0.5 units when testing a nutrient sample with two different pH meters
that have been correctly calibrated. Note that pH indicators cannot give
false readings (with colorless samples) because they will only respond to
hydrogen ions. |
