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21
the KP471 module, if no temperature probe or combined probe with temperature sensor is also
connected.
In
MTC
mode, in order to manually change the compensation temperature press °C/°F once: The
indicated temperature value starts blinking. Select the desired temperature value
by using the
and
arrows, and confirm with ENTER.
The display stops blinking, and the temperature displayed
is used for compensation.
During manual compensation, in order to change the unit of measurement between °C and
°F, it is necessary to press the °C/°F key twice
.
pH electrode calibration
The electrode calibration is used to compensate the asymmetry potential and slope departures to
which the electrode is subject with time.
The calibration frequency depends on the accuracy desired by the user and on the effects that the
measured samples have on the electrode. Generally, we recommend daily calibration, but it is the
user's responsibility from personal experience, to establish the most appropriate frequency.
The calibration may be carried out using one or more points (up to 5): when using 1 point, the
electrode offset is corrected, with 2 points the offset and the gain is corrected.
The instrument has a memory of 8 buffers with relevant temperature compensation tables (ATC)
plus a “CUSTOM” buffer, not compensated for temperature. The five buffers can be selected by
using the
BUFFER_1, …, BUFFER_5
menu items. Usually two for the acid, one for the neutral,
and two for the alkaline band will be selected:
@25°C
BUFR_1 (NEUTRAL)
6.860
7.000 7.648
BUFR_2 (ACID)
1.679
4.000
4.010
BUFR_3 (ALKALINE)
9.180
10.010
If no electrode calibration was carried out on the instrument, or the last calibration failed, or the
calibration validity period has expired, the measurement is blinking on the display and by pressing
the DISP key the
CAL
blinking message appears.
Calibration procedure
1. Select the buffer to be calibrated in the “pH Options” >> “pH Buffer Solutions” menu item
(please see the menu description on page
11
). This operation must be performed only the first
time or when the normal calibration buffers are changed.
2. Dip the SICRAM pH/temperature probe or the electrode linked to the KP471 module to be
calibrated and the temperature probe in the buffer selected for calibration. If no temperature
probe is available, use a thermometer and enter the value manually as indicated in the
paragraph “Automatic or Manual pH Compensation”.
3. The electrode calibration mode is started by pressing
CAL
followed by
F1=pH
.
4. The page shown in the figure will appear: From top to bottom there are:
•
The pH measurement value with the current calibration (7.015pH in the example)
•
The temperature compensated buffer value (in the figure 19.8°C
Æ
6.882): To modify this
last value use the arrow keys (
and
).
•
Offset and slope values after calibration: When you enter the calibration procedure, these
values are set to the factory values. When pressing F3=CAL, the actual conditions are
shown.
