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16.2 Glossary
Activity The activity corresponds to the effective concentration.
Due to a reciprocal interaction, the effect of ions, e.g. in
electrochemical processes, deviates from the expected
theoretical value. The activity of ions in small to medium
concentrations (< 1 mol/kg) is less than their
concentration. The relationship between the activity a and
the concentration c is expressed by the equation: a
i
=f
i
x
c
i
.
Adjusting To manipulate a measuring system so that the relevant
value (e. g. the displayed value) differs as little as possible
from the correct value or a value that is regarded as
correct, or that the difference remains within the tolerance.
Amperometry Name of a measuring technique. The signal (depending
on the measured parameter) of the probe is the electric
current. The electrical voltage remains constant.
Asymmetry Designation for the offset potential of a pH electrode. It is
the measurable potential of a symmetrical electrode, the
membrane of which is immersed in a solution with the pH
of the nominal electrode zero point (WTW electrodes: pH
= 7).
AutoRange Name of the automatic selection of the measuring range.
AutoRead WTW name for a function to check the stability of the
measured value.
Blank value Designation for the oxygen consumption of the BOD of the
dilution water.
The determination of the blank value is required to
calculate the BOD.
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