Hanna Instruments HI 2550 User Manual

Page 13

pppppH CALIBRATION

H 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

PREPARATION

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 or 9.18 as second buffer.
PROCEDURE

PROCEDURE

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:
• pH 1.68, 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
“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.