wtw Multi 197i Operating Manual page 81

Multi 197i
Measuring system
Molality
MultiCal
Offset potential
OxiCal
Oxygen saturation
pH value
Potentiometry
ORP voltage
Reference
temperature
Reset
Resistance
Resolution
Salinity
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The measuring system comprises all the devices used for measuring,
e. g. measuring instrument and sensor. In addition, there is the cable
and possibly an amplifier, terminal strip and armature.
Molality is the quantity (in Mol) of a dissolved substance in 1000 g sol-
vent.
®
WTW name stating that a measuring instrument provides several cal-
ibration procedures.
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. The asymmetry is part of the offset potential.
®
WTW name for a procedure to calibrate D. O. measuring systems in
water vapor saturated air.
Short name for the relative D. O. saturation.
Note: The D. O. saturation value of air-saturated water and the D. O.
saturation value of oxygen-saturated water are different.
The pH is a measure of the acidic or basic effect of an aqueous solu-
tion. It corresponds to the negative decadic logarithm of the molal hy-
drogen ions activity divided by the unit of the molality. The practical pH
value is the value of a pH measurement.
Name of a measuring technique. The signal (depending on the mea-
sured parameter) of the electrode is the electrical potential. The elec-
trical current remains constant.
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).
Fixed temperature value to compare temperature-dependent mea-
sured values. For conductivity measurements, the measured value is
converted to a conductivity value at a reference temperature of 20 °C
or 25 °C.
Restoring the original condition of all settings of a measuring system.
Short name for the specific electrolytic resistance. It corresponds to
the reciprocal value of the electrical conductivity.
Smallest difference between two measured values that can be dis-
played by a measuring instrument.
The absolute salinity S
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 is used for oceanographic monitoring. It is deter-
mined by measuring the electrical conductivity.
of seawater corresponds to the relationship
A
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