Why is the zero point measurement of the portable dissolved oxygen meter too high?
If you have another reliable dissolved oxygen meter, you can use the same test water sample for testing. If not, please check according to the following method.
The general dissolved oxygen meter generally conforms to the linearity of oxygen concentration/signal output, so the two-point calibration method is generally used:
1. Use anaerobic water solution to check the zero point;
2. Use oxygen-supersaturated water to verify whether the oxygen saturation value at the current temperature is consistent with the value measured by the instrument (please check the oxygen saturation value of clean water at each temperature)
The simple steps are as follows:
1. Take a certain amount of anhydrous Na2SO3 (anhydrous sodium sulfite) and prepare a sodium sulfite solution with a mass concentration of 5% (ready to use), which is an anaerobic solution. Use immediately after preparation, otherwise oxygen will slowly blend into the solution, resulting in The results are unreliable. During operation, insert the probe of the dissolved oxygen meter into the solution and move the probe slowly at the same time. When the reading is stable, see if the reading is close to zero. If it is close to zero, the zero point is accurate.
2. Take a certain amount of clean water, aerate it with micropores for 15 minutes, stop aeration, it is supersaturated water. During operation, insert the probe of the dissolved oxygen meter into the solution, and move the probe slowly at the same time. When the reading is stable, record the reading and measure at the same time. Check the water temperature at that time and check the dissolved oxygen concentration table of clean water for comparison.
Note that when completing step 1, clean the probe to avoid negative errors.
Introduction to saturated dissolved oxygen meter
The dissolved oxygen meter is suitable for the measurement of dissolved oxygen in different water quality and wastewater in various industries. Equipped with a high-performance polarographic sensor dissolved oxygen electrode, oxygen generates current through the specific dissolved oxygen HI2400-0 desktop dissolved oxygen/saturated dissolved oxygen meter [1] membrane, thereby ensuring measurement stability and accuracy; the dissolved oxygen measurement mode can be selected mg/ L (ppm) O2 or percent saturation dissolved oxygen %. This dissolved oxygen meter can be automatically calibrated in the air or select 1-point or 2-point calibration (0 or 100%). Altitude compensation and salinity compensation can be selected during measurement. Built-in automatic interval storage of 8000 measurement data memory, the stored data can be transferred to the computer through the USB data interface for further data analysis and management; the data can be downloaded to the computer for further analysis and management.
