Daily Maintenance of Online pH Meter

Online pH meter is also known as industrial pH transmitters. It consists of two parts, the measuring electrode (sensor) and meter, and is widely used in chemical, pharmaceutical, environmental protection, water supply, electric power and metallurgical industries for on-line real-time monitoring of water quality in various processes of industrial production. The accuracy of the measurement results is directly related to product quality control and production safety. Because of its installation and use of the environment is usually more harsh, in order to ensure the accuracy and reliability of the results of the online pH meter, need to be targeted for its maintenance and repair.

Common Failures of On-Line pH Meters

1. Obvious measurement error

Online pH meter is found to have obvious measurement error during online monitoring. When encountering this situation, it should be considered from the measured solution, glass electrode, electrode chamber, salt bridge, reference electrode and wiring. The measured solution pressure, temperature and flow rate do not meet the working conditions of the electrode, the glass electrode is contaminated, the salt bridge is blocked, the insulation around the electrode chamber is poor, the reference electrode is damaged or the wiring is poor, and so on, all of which will cause obvious measurement errors.

2. Measured value fluctuation

When the measured value has been fluctuating, it is difficult to reach a stable value, you should consider whether it is caused by the measured solution pressure or flow rate changes too quickly. In addition, it should also be considered whether the glass electrode is contaminated, the salt bridge is blocked or the measurement line insulation is poor.

3. Slow response during measurement

When this happens, the replacement rate of the measured solution should often be considered, and if the replacement rate is too slow, technical improvements should be made. In addition, check whether the glass electrode is not sufficiently immersed and whether the salt bridge is blocked.

4. Slow unidirectional drift of the measured value

When this happens during measurement, it is usually a problem with the electrode. Carefully inspect the glass electrode for cracks or pores. Also, check the reference electrode for air bubbles or leakage.

Routine Maintenance of Online pH Meters

Because of its harsh environment, the pH meter needs to follow a strict calibration and routine maintenance method.

( 1) Every 12 months should be a comprehensive maintenance of online pH meter. It is recommended to carry out calibration once every 3 months, and the calibration time can be extended or shortened according to the installation environment.

( 2) Clean the glass electrode and check the salt bridge. If the electrode is found to be deteriorated or there are micro holes or cracks on the bulb, the glass electrode should be replaced in time. Be very careful when checking and repairing, do not invert the glass electrode and do not touch the sensitive film of the glass electrode with your hands to avoid contamination and damage to the electrode.

( 3) Check the reference electrode as follows: Place the electrode system into the solution to be tested, and use a digital multimeter on the terminal board to measure the resistance between the reference electrode and the solution ground, which should not exceed 100kΩ.

( 4) Do not touch the touching terminals and connectors by hand, because they need a high degree of insulation, once the contact is contaminated insulation performance will be greatly reduced.

( 5) Check the internal condition of the instrument. Check that the seals are intact and that the cable connectors are clean and dry. Check the insulation condition with a megohmmeter.

Online pH meter plays a very important role in real-time monitoring in chemical, pharmaceutical, environmental protection, water supply, electric power and metallurgical industries, and should be regularly calibrated, regularly inspected, and timely maintained and troubleshooted in order to ensure the accuracy and reliability of its measurement performance.