Xylem pHotoFlex/pHotoFlex Turb - Manual (Page 101)

pHotoFlex / pHotoFlex Turb Lists
101 ba75491d04 07/2006
Glossary
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.
Analysis specification The exact proceeding to carry out the detection procedure is described
in the analysis specification.
Asymmetry 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).
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 (reagent
blank value)
The evaluation of the photometric measurement always refers to the
comparison value of a sample without the substance to be determined
(reagent blank value). Thus the influence of the basic absorbance of
the reagents on photometric measurement is compensated for.
Calibration Comparing the value from a measuring system (e. g. the displayed val-
ue) to the correct value or a value that is regarded as correct. Often,
this expression is also used when the measuring system is adjusted at
the same time (see adjusting).
Cell Vessel to take a liquid sample for measurement in a photometer.
The cell material (mostly glass) must have certain optical features to
be suitable for photometry.
Citation forms Different forms of representing a measured concentration value that
can be derived from each other.
The method to determine phosphate, e.g. delivers a measured value
for phosphorous P. This measured value can be alternatively quoted
in the citation forms, PO4, PO4-P or P2O5.
Detection procedure The detection procedure designates the general principle of how a
sample is brought into a form suitable for measurement.
Different methods can be based on the same detection procedure.
Electrode 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.
Electromotive force of
an electrode
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.