Calibrating - wtw pH 315i Operating Manual

pH 315i Operation
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 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.
Note
Always calibrate after replacing the pH electrode.
You can select between two calibration procedures:
AutoCal TEC 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 4.4 C ), the instrument
ONFIGURATION
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. To do this, the
instrument uses the standard slope (-59.2 mV/pH at 25 °C) and deter-
mines the asymmetry of the electrode.
AutoCal DIN is specially adapted to the permanently programmed buffer solutions in
accordance with DIN 19266 as a fully automatic two-point or three-
point calibration. The operating sequence of the AutoCal DIN calibra-
tion corresponds to that of the AutoCal TEC calibration. The calibration
can only be terminated after the first buffer solution (single point cali-
bration).
AutoRead When calibrating with AutoCal TEC and AutoCal DIN, the AutoRead
function is automatically activated.
The current AutoRead measurement can be terminated at any time
(accepting the current value) by pressing <RUN/ENTER>.
Displaying calibration Each time the instrument is switched on, the calibration data are shown
data on the display for a short time (see section 4.1 S -
WITCHING ON THE MEA
). In order to view the calibration data, switch the
SURING INSTRUMENT
measuring instrument off and switch it on again.
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