Hanna Instruments HI 253 Instruction Manual

Contents

10pH CALIBRATIONCalibrate the instrument frequently, especially if high accuracy is required.The instrument should be recalibrated :ï Whenever the pH electrode is replaced.ï At least once a week.ï After testing aggressive chemicals.ï If ìCALî ìINTVî tags are blinking during measurement.Every time you calibrate the instrument use fresh buffers and perform anelectrode Cleaning Procedure (see page 34).PREPARATIONPour small quantities of the buffer solutions into clean beakers. If possible, useplastic or glass beakers to minimize any EMC interferences.For accurate calibration and to minimize cross-contamination, use two beakersfor 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 andpH 4.01 as second buffer. If you are measuring in the alkaline range, use pH7.01 or 6.86 as first buffer and pH 10.01 or 9.18 as second buffer.PROCEDURECalibration has a choice of 5 memorized buffers: pH 4.01, 6.86, 7.01, 9.18and 10.01.It is recommended to perform a two or three-point calibration. However, theinstrument also allows one-point calibration, as described on page 12.THREE-POINT CALIBRATIONï Immerse the pH electrode and the temperatureprobe approximately 4 cm (1Ωî) into a buffersolution of your choice (pH 4.01, 6.86, 7.01, 9.18or 10.01) and stir gently. The temperature probeshould be close to the pH electrode.ï Press CAL. The ìCALî and ì 1BUF î tags will appearand the ì7.01î buffer will be displayed on thesecondary LCD.ï If necessary, press the ARROW keys to select a different buffer value.CAL1BUFFER pHBUFpH