Xylem CG 842 - Manual (Page 24)

Operation
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4.3 Calibrating
Why calibrate? pH electrodes age. This changes the asymmetry (zero
point) and slope of the pH electrode. As a result, an inexact
measured value is displayed. Calibration determines the
current values of the asymmetry and slope of the electrode
and they are stored in the instrument.
Thus, you should calibrate at regular intervals.
Note
Always calibrate after connecting another electrode.
You can choose between 3 calibration procedures:
AutoCal TEC is specially adapted to the Technical Buffer Solutions as a
fully automatic two-point calibration. The buffer solutions are
automatically recognized by the instrument.
The following values are available:
2.00; 4.00; 7.00; 10.00.
AutoCal DIN is specially adapted to permanently programmed buffer so-
lutions according to DIN 19266 as a fully automatic two-
point calibration. The buffer solutions are automatically rec-
ognized by the instrument.
The following values are available:
1.68; 4.01; 6.87; 9.18.
ConCal is the conventional two-point calibration with 2 freely
selectable buffer solutions or single-point calibration as the
rapid method.
AutoRead In calibration using AutoCal TEC and AutoCal DIN, the Au-
toRead function is automatically activated.
The current AutoRead measurement (with acceptance of
the current value) can be terminated at any time by pressing
<run/enter>.