Calibrating - wtw 330i Operating Manual

Operation
Why calibrate?
When to calibrate?
Calibration interval
AutoCal TEC
AutoCal DIN
ConCal
18
4.3

Calibrating

pH electrodes age. This changes the asymmetry (zero point) and slope
of the pH electrode. As a result, an inexact measured value is dis-
played. Calibration determines the current values of the asymmetry
and slope of the electrode and stores them in the measuring instru-
ment.
Thus, you should calibrate at regular intervals.
l After connecting another electrode
l When the sensor symbol flashes:
– after the calibration interval has expired
– after a voltage interruption, e. g. after changing the batteries
The calibration interval (Int 3) is set to 7 days in the factory. You can
select the interval in the range of 1 ... 999 days (see section
4.6 C ).
ONFIGURATION
You can select between 3 calibration procedures:
is specially adapted to the WTW technical buffer solutions as a fully au-
tomatic two-point or three-point calibration. The buffer solutions are
automatically recognized by the measuring instrument. Depending on
the instrument setting (see section 4.6 C
displays the relevant buffer nominal value or the current electrode volt-
age in mV. The calibration can be terminated after the first buffer solu-
tion. This corresponds to a single-point calibration. For this, the
instrument uses the Nernst slope (-59.2 mV/pH at 25 °C) and deter-
mines the asymmetry of the electrode.
is specially adapted to the permanently programmed buffer solutions in
accordance with DIN19266 as a fully automatic two-point or three-
point calibration. The buffer solutions are automatically recognized by
the measuring instrument. Depending on the instrument setting (see
section 4.6 C
ONFIGURATION
nominal value or the current electrode voltage in mV. The calibration
can be terminated after the first buffer solution. This corresponds to a
single-point calibration. For this, the instrument uses the Nernst
slope (-59.2 mV/pH at 25 °C) and determines the asymmetry of the
electrode.
This function is a conventional two-point calibration using two buffer
solutions (pH 7.0 ± 0.5 and any other buffer solution) or a single-point
calibration using any buffer solution and is used as a high-speed
method.
ONFIGURATION
), the instrument displays the relevant buffer
pH 330i/340i
), the instrument