Ph calibration – Hanna Instruments HI 254 User Manual

Page 9

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 30).
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 or pH 1.68 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 pH 12.45 as second buffer.
PROCEDURE

Calibration has a choice of 7 memorized buffers: pH 1.68, 4.01, 6.86, 7.01,

9.18, 10.01 and 12.45.

It is recommended to perform at least a two-point calibration. However, the

instrument allows up to five-point calibration, as described on page 11.
ONE-POINT CALIBRATION
Immerse the pH electrode and the temperature probe

approximately 4 cm (1½) into a buffer solution of

your choice (pH 1.68, 4.01, 6.86, 7.01, 9.18, 10.01

or 12.45) 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.

CAL

BUFFER pH

BUF