Glossary
Multi 9430
126
ba75966e04
04/2015
16 Glossary
pH/ORP/ISE
Conductivity
Asymmetry
see zero point
Electromotive force of
a combination
electrode
The electromotive force U of the combination electrode is the measur-
able electromotive force of an electrode in a solution. It equals the sum
of all the galvanic voltages of the combination electrode. Its depen-
dency on the pH results in the electrode function, which is characterized
by the parameters, slope and zero point.
Junction
The junction is a porous body in the housing wall of reference elec-
trodes or electrolyte bridges. It arranges the electrical contact between
two solutions and makes the electrolyte exchange more difficult. The
expression, junction, is also used for ground or junction-less transitions.
ORP voltage (U)
The ORP is caused by oxidizing or reducing substances dissolved in
water if these substances become effective on an electrode surface (e.
g. a gold or platinum surface).
pH value
The pH value is a measure of the acidic or basic effect of an aqueous
solution. It corresponds to the negative decadic logarithm of the molal
hydrogen ions activity divided by the unit of the molality. The practical
pH value is the value of a pH measurement.
Potentiometry
Name of a measuring technique. The signal (depending on the mea-
sured parameter) of the electrode is the electrical potential. The electri-
cal current remains constant.
Slope
The slope of a linear calibration function.
Zero point
The zero point of a pH combination electrode is the pH value at which
the electromotive force of the pH combination electrode at a specified
temperature is zero. Normally, this is at 25 °C.
Cell constant (C)
Characteristic quantity of a conductivity measuring cell, depending on
the geometry.
Conductivity (
ϰ
)
Short form of the expression, specific electrical conductivity.
It corresponds to the reciprocal value of the resistivity.
It is a measured value of the ability of a substance to conduct an electric
current. In water analysis, the electrical conductivity is a dimension for
the ionized substances in a solution.
Reference
temperature
Fixed temperature value to compare temperature-dependent measured
values. For conductivity measurements, the measured value is con-
verted to a conductivity value at a reference temperature of 20 °C or 25
°C.
Resistance (
ρ
)
Short name for the electrolytic resistivity. It corresponds to the recipro-
cal value of the electrical conductivity.
