Ph calibration – Hanna Instruments HI 255 User Manual

Page 12

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 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 45).
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 7.01or 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
Calibration has a choice of 5 memorized buffers: pH 4.01, 6.86, 7.01, 9.18

and 10.01.

It is recommended to perform a two or three-point calibration. However, the

instrument also allows a one-point calibration, as described on page 14.

Select pH range by pressing RANGE.
THREE-POINT CALIBRATION

_ Immerse the pH electrode and the temperature probe

approximately 4 cm (1½) into a buffer solution of

your choice (pH 4.01, 6.86, 7.01, 9.18 or 10.01)

and stir gently. The temperature probe should be

close to the pH electrode.

Press CAL. The CAL and

BUF

tags will appear and

the 7.01 buffer will be displayed on the secondary

LCD.

If necessary, press the ARROW keys to select a different buffer value.

BUFFER pH

BUF

CAL