5 | Bases for measurement
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B-H86.0.12.DB2-1.0
5 Bases for measurement
5.1 pH measurement
5.1.1 Explanation
The pH value describes the acidic or alkaline behaviour of an aqueous solution. A pH
value below 7 is acidic, a value above 7 is alkaline. A pH value of 7 is neutral.
The pH measurement is very precise, but also sensitive. The measured signals are
very weak and high-ohmic. This is the case, in particularly in low-ion media.
NOTE
In order to detect the pH value of a solution, it should always be recorded together
with the measurement temperature, because most liquids change their pH value with
the temperature.
The following must be observed:
– avoid interference, electrostatic charges, etc.
– keep plug contacts clean and dry
– prevent electrodes which do not have any special waterproof versions from exten-
ded immersion above the shaft
– calibrate electrodes sufficiently often. The can range from every hour to several
weeks, depending on the electrode and the application
– Use a suitable electrode
5.1.2 pH electrode
NOTE
Normally, so-called pH single-rod measuring chains are used. They include all neces-
sary components that are integrated in an electrode.
