13
pH CALIBRATION
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 day.
• 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 53).
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 pH7.01 or 6.86 as first buffer
and pH4.01 as second buffer. If you are measuring in the alkaline range,
use pH7.01 or 6.86 as first buffer and pH10.01 or 9.18 as second buffer.
PROCEDURE
Calibration can be performed at up to five‑points.
For accurate measurements, a three-point calibration is recommended.
The calibration buffer can be selected from the calibration buffer list
that includes the custom buffers and the memorized standard buffers:
• pH1.68, 4.01, 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. Up to two custom buffers can be set in SETUP menu
(see page 36). Each custom buffer value can be changed in a ±1.0 pH
window around the set value, during calibration, when it is selected; the
“Cust.” tag will be displayed.
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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