Xylem CG 843 - Manual (Page 25)

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.
When to calibrate? l After connecting another electrode
l When the sensor symbol flashes:
– after expiry of the calibration interval
– after a voltage interruption, e.g. battery change
You can choose between 3 calibration procedures:
AutoCal TEC is specially adapted to the Technical buffer solutions as a
fully automatic two or three-point calibration. The buffer
solutions are automatically recognized by the instrument.
The following pH values are available:
2.00, 4.00, 7.00, 10.00.
AutoCal DIN is specially adapted to permanently programmed buffer
solutions according to DIN 19266 as a fully automatic two or
three-point calibration. The buffer solutions are automati-
cally recognized by the instrument.
The following pH 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
AutoRead function is automatically activated.
The current AutoRead measurement (with acceptance of
the current value) can be terminated at any time by pressing
<run/enter>.