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H CALIBRATIONH 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).

PREPARATIONPREPARATION

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.

PROCEDUREPROCEDURE

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.

Hanna Instruments HI 2550 User Manual

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