9
Calibrate the instrument frequently, especially if high accuracy is
required.
The instrument should be recalibrated:
• Whenever the pH electrode is replaced.
• At least once a week.
• After testing aggressive chemicals.
• If “
CAL
” “
INTV
” tags are blinking during measurement.
Every time you calibrate the instrument use fresh buffers and perform an
electrode Cleaning Procedure (see page 26).
PREPARATION
Pour small quantities of the buffer solutions into clean beakers. If
possible, use plastic or glass beakers 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 first
buffer and pH 4.01 as second buffer. If you are measuring in the alkaline
range, use pH 7.01 or 6.86 as first buffer and pH 10.01, 9.18 as second
buffer.
PROCEDURE
Calibration can be performed up to three-points.
For accurate measurements, a three
-
point calibration is recommended.
However, a one or two point calibration can also be used.
The calibration buffers can be selected from the calibration buffer list that
includes custom buffers and the memorized standard buffers:
•
pH 4.01, 6.86, 7.01, 9.18
and
10.01.
The custom buffers allow the user to calibrate in a buffer solution different
from a standard one. Up to two custom buffers can be set in SETUP menu
(see page 17). Each custom buffer value can be changed in a ±1.0 pH
window around the set value (in according with temperature), during
calibration, when it is selected; the “
BUFFER pH
” tag will blink.
The instruments will automatically skip the buffer used during calibration
and the buffers which are in a ±0.2 pH window, around one of the
calibrated buffers.
All new calibrations will override existing stored calibration data in a
±0.2 pH window. The slopes adjacent to the new points will be reevaluated.
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