How to deal with common faults of online pH meters
1. Glass electrode aging
Phenomenon: response lag; sensitivity decrease; zero drift.
deal with:
⑴ Carry out electrode calibration regularly.
⑵Electrode activation: Aged electrodes can be soaked in a mixed solution of 1M acetic acid and 1M potassium chloride (1:1). After activation for 10 minutes, take them out and clean them. Electrodes that are not seriously aged can be activated by immersing them in distilled water or 0.1N dilute hydrochloric acid solution for 24 hours.
2. Glass electrode contamination
Phenomenon: sensitivity decrease; measurement deviation.
deal with:
⑴The alkaline precipitate on the electrode can be washed away in dilute hydrochloric acid solution, and then the electrode is cleaned with distilled water.
⑵The grease attached to the electrode can be cleaned with hot water and household detergent, or scrubbed with gauze.
⑶ Colloidal dirt can be cleaned with strong hydrochloric acid solution. After washing, be sure to clean the electrode with distilled water.
4. After cleaning with acid, alkaline solvent or organic solvent, the electrode should be soaked in distilled water for a period of time to restore the damaged hydration layer.
3. Reference electrode contamination (ceramic plug clogged)
Phenomenon: The measured value is too high; the indication is unstable.
Treatment: It can be cleaned with hot water and household detergent; oily or alkaline dirt can be cleaned with organic solvents (such as alcohol) or dilute hydrochloric acid solution; if the pollution is serious, it can be scrubbed with a soft brush or wiped with a filter paper strip. For non-flow electrodes, the electrode can be placed in the 80°C electrolyte until the electrolyte becomes cool.
4. Reference electrode poisoning
Phenomenon: erroneous indication; unstable indication; unable to correct.
Treatment: If the electrolyte in the reference electrode is only contaminated, replace the electrolyte; if the non-flow electrode or the internal electrode is poisoned, the electrode needs to be replaced.
5. The signal cable’s impedance to ground is reduced (<107Ω)
Phenomenon: The indication is unstable and jumps; the display is out of range and cannot be measured.
Treatment: Replace the cable and dry the cable plug or junction box with a hair dryer.
