How to reduce the measurement error of acid rain pH meter
Maintenance of composite electrode
(1) After removing the electrode cover, avoid contact between the sensitive glass bulb of the electrode and hard objects, because any damage or scratches will cause the electrode to fail.
(2) After measurement, put on the electrode protective cover in time. A small amount of external reference supplementary liquid should be placed in the electrode cover to keep the electrode bulb moist. Do not soak it in distilled water.
(3) The external reference supplement solution for the composite electrode is 3mol/L potassium chloride solution. The amount of the solution should be kept at more than 1/2 of the inner cavity capacity and less than 1/2. Use a dropper to add it from the small hole at the upper end of the electrode. . When the composite electrode is not in use, the rubber cover should be pulled up to prevent the replenishing fluid from drying up.
(4) The lead-out of the electrode must be kept clean and dry to prevent short circuit at both ends of the output. The electrode should avoid being immersed in distilled water or other protein solutions and acidic fluoride solutions for a long time. The electrode should also avoid contact with silicone oil.
(5) The service life of composite electrodes is generally one year, and the measuring station should regularly replace new composite electrodes in April every year. During the period of use, if the slope is found to be slightly reduced, the lower end of the electrode can be soaked in 4% HF (hydrofluoric acid) for 3 to 5 seconds, washed with distilled water, and then soaked in 0.1mol/L hydrochloric acid solution to make it recover.
Analysis and Troubleshooting of Common Instrument Faults
In actual work, aging of equipment components, improper operation methods, and unstable power supply voltage will cause failures of the pHS-3B-S pH meter, making it difficult to correctly obtain acid rain observation data. Observers are required to conduct troubleshooting for any malfunctions that occur. Provide timely and accurate diagnosis, analysis and troubleshooting to ensure the normal development of acid rain observation services.
(1) The power is turned on but there is no display. Possible causes and solutions:
a. The fuse is broken and should be replaced;
b. The power supply or transformer is broken and should be sent for repair or replacement;
c. The instrument circuit is faulty and should be sent for repair.
(2) "Positioning" cannot adjust the pH value to 7.00. Possible reasons and solutions:
a. When the composite electrode replenishing solution dries up, replenish 3M potassium chloride solution or replace the electrode;
b. The composite electrode fails and should be replaced;
c. The internal potentiometer is broken and should be sent for repair or replacement.
(3) The "slope" adjustment cannot reach a pH value of 4.00 or a pH value of 9.18. Possible reasons and solutions:
a. The composite electrode ages and its performance decreases and should be replaced;
b. The internal potentiometer is broken and should be sent for repair and replacement.
(4) When measuring pH value, the reading is unstable. Possible reasons and solutions:
a. The K value of the water sample is too low (such as lower than 10 μS/cm), and the equilibrium time should be appropriately extended;
b. The internal resistance of the composite electrode is too high, its lifespan has expired, and it should be replaced;
c. The composite electrode plug (seat) is damp or contaminated. You should turn off the machine and wipe the composite electrode plug (seat) with 95% alcohol, and dry it before use;
d. If the power supply voltage is unstable or the ground wire is in poor contact, you should turn off the machine and weld the ground wire firmly, and then turn on the machine for measurement after the voltage is stable.
(5) During "automatic" compensation, the digital overflows or the displayed value is unstable. Possible reasons and solutions:
a. The temperature measuring probe is not connected properly or is broken. It should be connected or replaced;
b. The temperature compensation selector switch is broken and should be repaired or replaced;
c. The internal wire of the temperature measurement probe jack is broken and should be sent for repair;
d. The instrument circuit is faulty and should be sent for repair.
