Upkeep and Repair of the Dissolved Oxygen Meter
1. Dissolved oxygen electrode cleaning calibration, regeneration, maintenance and maintenance
1) The electrodes of the dissolved oxygen meter should be cleaned once every 1 to 2 weeks. If there are pollutants on the diaphragm, it will cause measurement errors. Care should be taken when cleaning, taking care not to damage the diaphragm. Rinse the electrode of the dissolved oxygen meter in clean water. If the dirt cannot be washed off, carefully scrub it with a soft cloth or cotton cloth.
2) The zero point and span should be re-calibrated every 2 to 3 months.
3) Regeneration of the electrode of the dissolved oxygen meter is performed about 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 the silver electrode is observed to be oxidized, it can be polished with fine sandpaper.
4) If the dissolved oxygen electrode leaks during use, the electrolyte must be replaced.
2. Dissolved oxygen meter calibration and calibration: Generally, standard liquid calibration or on-site sampling calibration can be used.
1) Standard solution calibration method: Standard solution calibration generally adopts two-point calibration, that is, zero point calibration and span calibration. The zero point calibration solution can use 2% Na2SO3 solution. Range calibration solution can choose 4M KCl solution (2mg/L) or 50% methanol solution (21.9mg/L) according to the measurement range of the meter.
2) On-site sampling calibration method (Winkler method): In actual use, the Winkler method is often used for on-site calibration of dissolved oxygen analyzers (dissolved oxygen meters). When using this method, there are two situations: when sampling, the meter reading is M1, and the analytical value is A. When the meter is calibrated, the meter reading is still M1. At this time, it is only necessary to adjust the meter reading to be equal to A; when sampling, the meter reading is M1, the laboratory analysis value is A, and the meter reading is changed to M2 when the meter is calibrated. At this time, the meter reading cannot be adjusted to be equal to A, but the meter reading should be adjusted to 1MA × M2.
3) Dissolved oxygen electrode regeneration: The signal impedance of the dissolved oxygen electrode is relatively high (about 20MΩ), and the distance between the dissolved oxygen electrode and the converter is 50m; the dissolved oxygen electrode should also be in working condition when not in use, and can be connected to the dissolved oxygen converter . Electrodes that have been placed for a long time or regenerated (replace the electrolyte or membrane) should be polarized in an oxygen-free environment for 1 to 2 hours before use; since temperature changes have a great impact on the diffusion of the electrode membrane and the solubility of oxygen, it is necessary to For a long time (about 10 minutes) to make the temperature compensation resistance reach a balance; the partial pressure of oxygen is related to the altitude of the area, and the meter must be compensated according to the local atmospheric pressure before use; when the salt content of the measuring solution is high, the meter should be calibrated Use a solution with a comparable salt content; for the flow-through measurement method, a minimum flow velocity of 0.3m/s is required to flow through the electrode.
