Operational Guide
22
pH
Calibration
Preparation
Pour small quantities of the buffer solutions into clean beakers. If possible,
use plastic to minimize any EMC interferences. For accurate calibration and to
minimize cross-contamination, use two beakers for each buffer solution; one
for rinsing the electrode and one for calibration. If you are measuring in the
acidic range, use pH 7.01 or 6.86 as the first buffer and pH 4.01 (or 3.00*) as the
second buffer. If you are measuring in the alkaline range, use pH 7.01 or 6.86 as
first buffer and pH 10.01 or 9.18 as the second buffer.
* pH 3.00 is only visible when using specific pH electrodes and will replace 4.01
pH buffer.
Procedure
Calibration can be performed using up to five calibration buffers. For accurate
measurements, a minimum of a three-point calibration is recommended. The
calibration buffer can be selected from the calibration buffer list that includes
the custom buffers and the standard buffers:
pH 1.68, 4.01 (pH 3.00), 6.86, 7.01, 9.18, 10.01 and 12.45.
The custom buffers allow the user to calibrate in a buffer solution different from
a standard one. Two custom buffers can be set in SETUP menu. See page 23 for
more information about using custom buffers.
The instrument will automatically skip custom buffers which are in a ±0.2 pH
window of an already calibrated buffer.
Submerse the pH electrode approximately 3 cm (1¼”) into a buffer solution and
stir gently. Press
CAL
to enter calibration.
The “CAL” tag will appear and the “7.01” buffer will be
displayed on the third LCD line. If necessary, press the
ARROW
keys to select a different buffer value. The “ ”
along with “STIR” tag will be displayed and “WAIT” will
blink on the LCD until the reading is stable.
When the reading is stable and close to the selected
buffer, “CFM” tag will blink. Press
CFM
to confirm
calibration.
After confirming the first point, the calibrated value
will be displayed on the first LCD line and the second
expected buffer value on the third LCD line (i.e. pH
4.01).
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