wtw pH 315i Operating Manual page 41

pH 315i
Adjusting
Asymmetry
AutoRange
AutoRead
Calibration
Diaphragm
Electrode voltage
Electrode zero point
Measured parameter
Measured value
Measuring system
Molality
MultiCal
Glossary
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 with-
in the tolerance.
Designation for the offset potential of a pH electrode. It is the measur-
able 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).
Name of the automatic selection of the measuring range.
WTW name for a function to check the stability of the measured value.
Comparing the value from a measuring system (e. g. the displayed
value) to the correct value or a value that is regarded as correct. Of-
ten, this expression is also used when the measuring system is adjust-
ed at the same time (see adjusting).
The junction is a porous body in the housing wall of reference elec-
trodes or electrolyte bridges. It forms the electrical contact between
two solutions and makes electrolyte exchange more difficult. The ex-
pression, junction, is also used for ground or junction-less transitions.
The electromotive force U of the electrode is the measurable electro-
motive force of an electrode in a solution. It equals the sum of all the
galvanic voltages of the electrode. Its dependency on the pH results
in the electrode function which is characterized by the parameters,
slope and zero point.
The zero point of a pH electrode is the pH value at which the electro-
motive force of the pH electrode at a specified temperature is zero.
Normally, this is at 25 °C.
The measured parameter is the physical dimension determined by
measuring, e. g. pH, conductivity or D. O. concentration.
The measured value is the special value of a measured parameter to
be determined. It is given as a combination of the numerical value and
unit (e. g. 3 m; 0.5 s; 5.2 A; 373.15 K).
The measuring system comprises all the devices used for measuring,
e. g. measuring instrument and probe. 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.
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