NAVI D-25 Instruction Manual page 190

7 Reference
7.1 pH measurement
● Using standard solutions
Standard solutions are used to calibrate the scale of the
pH meter employed to measure the unknown pH of a
solution. Standard solutions of pH 4, 7, and 9 are used in
combination according to the particular conditions of the
solution that is to be inspected.
When the approximate pH value is desired (1-
point calibration)
Use the pH 7 standard solution or a standard solution
that approximates the pH value of the solution that is to
be inspected.
When it is known beforehand whether the test
solution is acidic or alkaline (2-point calibration)
Acidic: Use the pH 4 and 7 standard solutions.
Alkaline: Use the pH 7 and 9 standard solutions.
When an unknown solution is to be inspected (3-
point calibration)
Use the pH 4, 7, and 9 standard solutions.
Other
When finding the pH of other solutions, perform 2-point
or 3-point calibration using pH 2, 4, 7, 9, or 12 standard
solutions randomly, then measure the test solution.
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