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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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Hanna Instruments HI 2212 User Manual

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