wtw inoLab 740, Operating Manual

Page: 76 / 274

pH
76
6.2 Calibrating pH measurements
Why calibrate? pH electrodes age. This changes the asymmetry and slope
of the pH electrode. This may cause the measuring system
to ignore the limits of a calibrated system. Calibration
determines the current values of the asymmetry and slope
and stores them in the measuring module.
Calibration must be performed at regular intervals.
Note
Always calibrate after replacing the pH electrode.
You can choose between two calibration procedures:
AutoCal and ConCal :
AutoCal is a fully automatic calibration using the datasets selected
for buffer solutions in the
pH buffer menu.
ConCal is the conventional two-point calibration method and single-
point calibration is the simplified calibration method.
AutoRead When calibrating with AutoCal, the AutoRead function is
automatically activated.
The current AutoRead measurement can be terminated at
any time (accepting the current value) by pressing
g
.
Calibration record The calibration record contains the calibration data of the
current calibration. You can call up the calibration record by
outputting the data storage (section 11.3).
Note
You can automatically print a calibration record following
calibration. To do so, switch on the printer before calibrating
(print LED lights up green). After a valid calibration, the
record is printed.