Multi 3320
Glossary
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17 Glossary
pH/ORP/ISE
Dissolved oxygen
Asymmetry
see zero point
Electromotive force of
an electrode
The electromotive force U of the electrode is the measurable electromo-
tive force of an electrode in a solution. It equals the sum of all the gal-
vanic voltages of the electrode. Its dependency 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
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 electrode is the pH value at which the electromo-
tive force of the pH electrode at a specified temperature is zero. Nor-
mally, this is at 25 °C.
D.O. partial pressure
Pressure caused by the oxygen in a gas mixture or liquid.
D.O. saturation
Short name for the relative D.O. saturation.
OxiCal
®
Name for a procedure to calibrate D.O. measuring systems in water
vapor-saturated air.
Salinity
The absolute salinity S
A
of seawater corresponds to the relationship
of the mass of dissolved salts to the mass of the solution (in g/Kg). In
practice, this dimension cannot be measured directly. Therefore, the
practical salinity according to IOT is used for oceanographic monitor-
ing. It is determined by measuring the electrical conductivity.
Salt content
General designation for the quantity of salt dissolved in water.
Slope (relative)
The relative slope expresses the relation of the slope value to the
value of a theoretical reference sensor of the same construction type.
