As a key instrument for continuously measuring the pH of a solution in an industrial process, the correct maintenance and maintenance of the glass electrode of the industrial pH meter directly affects the measurement accuracy and equipment life.
Common problems and maintenance measures
Temperature has a significant effect on electrode measurements, and fluctuations in the temperature of the solution can cause changes in the electrode potential, which requires automatic temperature compensation in the converter feedback circuit by a temperature electrode (e.g., Pt100 or Pt1000) to eliminate the influence of temperature on measurement accuracy.
When the pH of the solution exceeds the range of pH2-pH9, the linear relationship of the glass electrode will deteriorate, the strong acidic solution is easy to increase the pH value measurement, the strong alkaline medium will lead to a low pH value, and the strong oxidizing medium may also cause electrode poisoning.
The electrode needs to be soaked in distilled water or 0.1N dilute hydrochloric acid for 24 hours to activate, and the electrode with severe aging can be activated with 1M acetic acid and 1M potassium chloride mixed solution (1:1) for 10 minutes.
Signal cable contamination, water ingress, damage, etc. will lead to a decrease in impedance, making the measurement signal unstable, the cable needs to be replaced and the plug dried with a hair dryer, and at the same time, a highly insulated cable should be used to ensure that the electrode leads are installed separately from the AC power supply, and the measurement device needs to be "floated" to prevent electrode polarization.
The electrode is easy to be wrapped by oil stains, colloids or sediments for a long time, resulting in slow response, so you can choose a flat surface self-cleaning electrode, or install regular automatic brushing, ultrasonic cleaning and other devices, or install filtration and separation equipment in front of the measuring cell.
Essentials for daily maintenance
Regular calibration of the electrode is the key to ensure the accuracy of the measurement, you can use a standard buffer solution to introduce into the measuring cell or take a sample at the measurement point to calibrate with a precision pH meter, the calibration period is determined according to the measurement conditions and accuracy requirements, generally a few days to a month, and the temperature of the calibration solution should be as consistent as possible with the temperature of the sample solution.
The glass electrode that has not been used for a long time needs to be washed with attached grease or solid precipitation, and the colloidal dirt can be cleaned with hydrochloric acid solution, and then soaked in 3M potassium chloride solution for preservation.
After a period of use, the electrode should be removed for activation and rotated, and the replacement cycle should be 1-2 months lower than the aging cycle to prolong the service life.
The electrode that has been activated after aging or poisoning should not be used in the process of poor medium environment and high detection requirements, but can be changed to the pH detection of aqueous medium, and should be replaced in time when the sensitivity of the electrode is lower than 25mV/pH.
summary
The maintenance and maintenance of industrial pH meter electrodes need to pay full attention to the influence of temperature, solution pH, glass film activity, signal cable impedance and electrode pollution, etc., through scientific temperature compensation, cleaning and activation, calibration and replacement and other measures, which can not only ensure the accuracy of measurement data, but also effectively extend the service life of the electrode, and provide reliable support for the stable control of industrial production processes.
