RADIOMETER ABL800 FLEX, Справочное руководство

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1. Potentiometric measuring principles ABL800 FLEX Reference Manual
General information,
Continued
Status Status reflects the deviation from the theoretical electrode at pH 7.400 and,
therefore indicates the position of the calibration line.
Theoretical calibration
line drawn through the 1-
point calibration point.
pH
Measured
potential
(mV)
E
Cal 1
pH
Cal 1
Theoretical calibration line for the
theoretical pH electrode with known
potential of
−
112.4 mV at a pH =
7.400.
E
Cal 1 nom
E
Cal 1 nom(theo)
E=
−
112.4 mV
pH
Cal 1 nom
(7.400)
pH
Status
∆
E
∆
pH
A calibration
line with the
same slope as
the theoretical
calibration line
(
−
61.5 mV/
pH) is drawn
through this
point.
The calibration line for the actual electrode deviates from that of the theoretical
electrode. The status value describes this deviation.
Status of the actual pH electrode at pH 7.400 is calculated as:
100 5 . 61
400 . 7 . 400 . 7 .
400 . 7
×
−
− =
at electr l theoretica of Potential at potential Meas
Status
Each electrode has its own status limits.
Drift Drift of an electrode is a measure of stability obtained by comparing the last
accepted calibration with the previous calibration.
The following drift values are used:
•
Drift 1 - obtained on Cal 1 and/or Gas 1;
•
Drift 2 – obtained after a 2-point calibration.
The obtained drift values should not exceed the calibration drift tolerances. The
drift tolerances can be changed in the Setup program, but Radiometer recommends
using the default drift tolerances. Too narrow drift tolerances will cause electrode
drift errors even for normal electrode fluctuations. If the drift tolerances are made
wider, no warning will be given if the electrodes should become unstable.
Significant measurement errors could result.
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