Introduction to the Calibration Procedure of Conventional pH Meters
The calibration procedure for conventional pH meters applies to commonly used online pH meters and laboratory pH meters, which are affordable for general users.
① Prepare suitable pH standard buffer solutions in the laboratory. Select any two of pH 4.01, pH 6.86 and pH 9.18 according to the fluctuation range of on-site water samples. If the on-site water is frequently acidic, choose pH 4.01 and pH 6.86 buffer solutions. If the on-site water is frequently alkaline, choose pH 6.86 and pH 9.18 buffer solutions.
② Remove the sensor from the site and rinse the glass electrode of the probe with clean water.
③ Pour the two standard buffer solutions into two prepared beakers respectively.
④ Immerse the electrode into the first standard buffer solution, open the instrument menu and perform the first-point calibration. Instruments of different brands have different menu operations for calibration. Follow the operation manual supplied with the instrument.
⑤ After the first-point calibration is completed successfully, rinse the electrode with clean water, then immerse the electrode into the second standard buffer solution, navigate the instrument menu and perform the second-point calibration.
⑥ After two-point calibration, instruments of different brands display the calibration pass or fail status in different ways.
⑦ If calibration passes, put the electrode back into the measured liquid and start the instrument.
⑧ If the instrument calibration fails, repeat the above calibration process once more. If calibration still cannot pass, replace the pH electrode. The service life of a pH electrode is generally about two years.
