4 ph calibration, Ph calibration – Xylem MULTI 3400 MULTI-PARAMETER METERS User Manual
Page 20
Operation
Multi 3400i
20
4.2.4
pH calibration
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.
When to calibrate?
z After connecting another electrode
z When the sensor symbol flashes:
– after the calibration interval has expired
– after a voltage interruption, e. g. after changing the batteries
AutoCal TEC
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
), the instrument displays the
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.
AutoRead
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
Displaying the calibra-
tion data
You can view the data of the last calibration on the display. The pro-
ceeding is described on page 48.
Printing the
calibration protocol
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
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.