Ph Calibration - wtw Multi 340i Operating Manual

Operation
Why calibrate?
When to calibrate?
AutoCal TEC
AutoRead
Displaying the calibra-
tion data
Printing the
calibration protocol
20

4.2.4 pH calibration

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
is specially matched to the WTW technical buffer solutions as a fully au-
tomatic two-point calibration. The buffer solutions are automatically
recognized by the measuring instrument. Depending on the instrument
setting (see section 4.8 C
relevant buffer nominal value or the current electrode voltage in mV.
The calibration can be terminated after the first buffer solution. This cor-
responds to a single-point calibration. To do this, the instrument uses
the Nernst slope (-59.2 mV/pH at 25 °C) and determines the asymme-
try of the electrode.
The calibration procedure automatically activates the AutoRead func-
tion.
The current AutoRead measurement can be terminated at any time
(accepting the current value) by pressing <RUN/ENTER>.
You can view the data of the last calibration on the display. The pro-
ceeding is described on page 48.
The calibration record contains the calibration data of the current cali-
bration. You can transmit the calibration protocol to a printer via the se-
rial interface (see O
UTPUTTING THE CALIBRATION PROTOCOL ON THE
, page 51).
INTERFACE
Note
You can automatically print a calibration record after the calibration. To
do so, connect a printer to the interface according to section 4.7.2 be-
fore calibrating. After a valid calibration, the record is printed.
), the instrument displays the
ONFIGURATION
Multi 340i