1.
Before measuring pH ensure that the nutrient is well stirred, especially
after pH UP and DOWN are used. This is one of the most common mistakes
made when testing pH (or conductivity). Also, ensure that the sampling
container is clean.
2. When the pH electrode is placed in a sample, you may
notice that the reading varies for some time (maybe several minutes)
before resting on a final value. There may be a difference in excess of 1
pH unit between the initial and final pH value. Since the “final value”
will be the most accurate, ensure you wait enough time for the reading to
stabilize (Fig 1.5a). However, note exceptions in the section “Preventing
contamination”.
3. Do not immerse the electrode in the sample to a depth that
exceeds the level of the filling solution inside of the electrode (Fig
1.5b). Since it is not possible to view the depth of the filling solution
(gel) in many pocket sized meters, immerse the electrode to a depth of no
more than ~20mm (3/4 inch). Exceeding this depth can permit the sample
solution to weep back into the electrode itself resulting in inaccurate
readings.
4. Once the reading has been taken, immediately remove the
electrode from the sample and rinse with distilled water. Failure to do so
will cause rapid deterioration of the electrode. Whilst not in use, store
the electrode in a properly formulated
storage solution.
