Correct calibration method of dissolved oxygen meter electrode
The calibration problem of the dissolved oxygen meter (dissolved oxygen meter electrode) is a problem that many people encounter, but few can solve it. They all rely on their own practical experience. In that case, it will be a strong guide to errors. You must There are scientific guidance methods. The most common instructions are the calibration instructions for the pH meter electrode. Today I will briefly explain the calibration of the electrode of the dissolved oxygen meter, so that everyone will no longer be confused when actually operating the dissolved oxygen meter. This article explains how to calibrate (or calibrate) the dissolved oxygen meter electrode and the future use and maintenance of the electrode.
1. Calibration method of dissolved oxygen meter: Dissolved oxygen meter can generally be calibrated with standard liquid or on-site sampling.
(1) Dissolved oxygen meter standard solution calibration method: Standard solution calibration generally uses two-point calibration, namely zero-point calibration and span calibration. The zero point calibration solution can use 2% Na2SO3 solution. The range calibration solution can be selected according to the instrument measurement range: 4M KCl solution (2mg/L); 50% methanol solution (21.9mg/L).
(2) On-site sampling calibration method of dissolved oxygen meter (Winkler method): In the actual use of dissolved oxygen meters, the Winkler method is often used for on-site calibration of dissolved oxygen analyzers. There are two situations when using this method: when sampling, the meter reading is M1, and the laboratory analysis value is A. When the meter is calibrated, the meter reading is still M1. At this time, you only need to adjust the meter reading to equal A; when sampling, the meter reading is M1, the laboratory analysis value is A. When the meter is calibrated, the meter reading changes to M2. At this time, the meter reading cannot be adjusted to be equal to A, but the meter reading should be adjusted to 1MA×M2.
2. Use and maintenance of dissolved oxygen meter electrodes
(1) The dissolved oxygen meter electrode should be cleaned once every 1 to 2 weeks. If there are contaminants on the diaphragm, it will cause measurement errors. Be careful not to damage the diaphragm when cleaning. Rinse the dissolved oxygen meter electrode in clean water. If the dirt cannot be washed away, wipe it carefully with a soft cloth or cotton cloth.
(2) The zero point and range of the dissolved oxygen meter electrode should be recalibrated every 2 to 3 months.
(3) The dissolved oxygen meter electrode should be regenerated approximately once a year. When the measurement range cannot be adjusted, the dissolved oxygen electrode needs to be regenerated. Electrode regeneration includes replacing the internal electrolyte, replacing the diaphragm, and cleaning the silver electrode. If oxidation is observed on the silver electrode, polish it with fine sandpaper.
(4) If leakage of the dissolved oxygen meter electrode is found during use, the electrolyte must be replaced.
