wtw Multi 340i Operating Manual page 8

pH calibration
pH
C t 1
2 8
4
°
AutoCal TEC
pH
C t 2
2 4 8
°
AutoCal TEC
pH
mV/pH
5 9 4
pH
mV
2
8
AutoCal TEC procedure (single and two-point calibration):
l Connect the pH electrode to the measuring instrument.
If necessary, press the <M> key until the status display pH (pH measure-
ment) or U (measurement of the ORP voltage) appears.
l Press the <CAL> key. The Ct1 display and the function display AutoCal
TEC appears. The sensor symbol displays the evaluation of the last cal-
ibration (or no sensor symbol in the delivery state or after the measure-
ment parameter has been reset).
C
TP
l Immerse the pH electrode into the first buffer solution.
l When measuring without a temperature sensor:
Enter the temperature of the first buffer solution with < > < > while
pressing the <RUN/ENTER> key.
l Press <RUN/ENTER>. The AutoRead measurement begins. The elec-
trode voltage (mV) or the buffer nominal value appears on the display. If
the measured value is stable, Ct2 appears.
Note
At this point, the AutoCal TEC calibration can be terminated
with <M>. This corresponds to a single-point calibration.
To do this, the instrument uses the Nernst slope (-59.2 mV/pH
C
TP
at 25 °C) and determines the asymmetry of the electrode.
l Immerse the two-point calibration pH electrode in the second buffer so-
lution to continue.
l When measuring without a temperature sensor:
Enter the temperature of the second buffer solution with < > < > while
pressing the <RUN/ENTER> key.
l Press <RUN/ENTER>. The AutoRead measurement begins. The elec-
trode voltage (mV) or the buffer nominal value appears on the display.
l When the measured value is stable, the instrument displays the value of
the slope and the calibration evaluation.
l Press <RUN/ENTER>. The instrument displays the value of the asym-
metry.
l Switch to the measuring mode with <M>.
Multi 340i