The following are detailed usage guidelines for the dissolved oxygen rapid measurement instrument for water quality, covering the operation process, key details, and precautions to assist users in obtaining accurate and stable measurement results:
1、 Preparation before startup
1. Equipment self inspection and preheating
-When in use or not in use for a long time, turn on the sensor and preheat it for 10-15 minutes in advance to make it reach a stable working state.
-Check if the display screen is displaying normally and if the battery is fully charged (if the battery is low, replace the alkaline battery in a timely manner).
2. Preparation of calibration solution
-Select standard solution based on measurement range: saturated air-water (about 8mg/L) is used for clean water bodies, and zero oxygen water (sodium sulfur solution) is used for two-point calibration in sewage or high pollution scenarios.
-Standard solution should be prepared and used immediately to avoid concentration changes caused by volatilization or oxidation.
3. Electrode maintenance
-Observe whether the membrane head is intact and undamaged. If there is any damage, yellowing, or attachment of impurities, immediately replace the membrane head with a new one and inject fresh electrolyte.
-Gently wipe the surface of the film head with a damp cotton swab to remove residual dirt, and do not use force to scrape to avoid damaging the sensitive layer.
2、 On site measurement operation process
1. Water sample collection and pretreatment
Representative sampling: Slowly immerse the probe into water to a specified depth (avoiding oil film on the water surface and sediment at the bottom), maintain a flowing state for measurement to avoid interference from local oxygen deficient areas.
Bubble avoidance: Ensure that the probe is submerged in water and there are no bubbles attached. After vigorous agitation, let it stand for 30 seconds until the water sample stabilizes.
Special scenario handling: Water samples containing suspended solids need to be equipped with protective covers; High temperature water bodies (>40 ℃) should shorten the measurement time to prevent electrolyte loss.
2. Key points of measurement operation
Principle of stable reading: Record data when the numerical fluctuation is less than ± 0.1mg/L and lasts for more than 10 seconds, avoiding capturing instantaneous peak or valley values.
Mixing control: When manually mixing, the action is gentle, and the speed of the automatic mixer does not exceed 200rpm to prevent the generation of vortices and the introduction of air bubbles.
Multi location retesting: Select at least 3 different points in the same water area for measurement, and take the average to improve data reliability.
3、 Data processing and storage
1. Real time recording: synchronously record environmental parameters such as measurement time, location, water temperature, atmospheric pressure, etc., and establish a complete data chain.
2. Abnormal value judgment: If the reading remains below 80% of the theoretical saturation value, it is necessary to check whether the membrane head is blocked or the electrolyte is depleted.
3. Data storage: Use the instrument's built-in memory or Bluetooth to transmit to the mobile device to avoid the loss of paper records.
4、 Daily maintenance and troubleshooting
-Daily maintenance: Rinse the electrode with deionized water after measurement, invert and drain, and store in a cool place.
-Weekly calibration: Use standard solution to verify the instrument's indication error. If the deviation exceeds ± 0.2mg/L, recalibration is required.
-Common troubleshooting:
-High reading → Check if there are scratches or cracks on the film head;
-Slow response → replace aging electrolyte;
-Serious drift → Clean the gold ring contacts inside the electrode.
5、 Safety precautions
Do not replace batteries or perform welding operations in flammable and explosive environments;
Waste electrolyte should be treated as hazardous waste and cannot be directly poured into the sewer.
When not in use for a long time, the battery should be removed and powered on once a month to prevent capacitor failure.