Analysis of Abnormal Measurement Values of Dissolved Oxygen Meter
Theoretically, the instrument probe has a linear response. After calibration at the zero point and the highest range point, the data used by the instrument to measure dissolved oxygen in water is acceptable. If you feel that the water sample test results are abnormal, you can use iodometric titration to compare and determine whether it is dissolved. There is a problem with the oxygen meter measurement results. If the relative deviation between the results of the iodometric method and the electrochemical probe method is within ±5%, the probe method measurement data is considered to be within the error range. If the relative deviation from the iodometric method exceeds the range of ±5% or the electrochemical probe response is not linear, you need to check the performance status of the dissolved oxygen instrument, such as whether it needs to be recalibrated, replace the electrode breathable membrane, fill the internal electrode with liquid, or polish and maintain the electrode, etc. .
Instrument use and maintenance
(1) After the instrument needs to be powered on, the electrode must be polarized for 0.5h before starting measurement or calibration;
(2) Under normal circumstances, zero-point calibration can be performed once a month, and water-saturated air calibration must be performed every time the instrument is used; in addition, the linearity of the probe response should be checked every two months;
(3) Clean the probe with pure water after use. Do not damage the breathable membrane during cleaning. Store the probe in the protective cover after use and keep the sponge in the protective cover moist. Check the electrode every 1 to 2 weeks when not in use. The probe undergoes cleaning and maintenance;
(4) It is recommended to replace the internal filling fluid of the electrode every 2 months. The instrument needs to be recalibrated after each replacement of the internal filling fluid. When replacing the internal filling fluid, first use the filling fluid to rinse the electrode and the inside of the electrode cover. When filling, first remove the electrode cover. Fill it with filling fluid, then slowly screw the electrode onto the sleeve vertically, making sure there are no bubbles inside the electrode.
(5) Regenerate the dissolved oxygen electrode every year, including replacing the internal electrolyte, replacing the breathable membrane, and cleaning the silver electrode; if there is oxidation on the surface of the silver electrode, it needs to be polished with fine sandpaper;
(6) When measuring, the probe is repeatedly stirred in the water body for measurement. The relative speed of the water flow is greater than 0.3m/s or the magnetic stirrer is rotated at 500rpm to measure the water sample. The speed is too high or too low, which will lead to data distortion. Air bubbles must be prevented during measurement. Remain on the diaphragm and affect the results.
