Maintenance and precautions for the pH meter (PH meter)
1) Maintenance and precautions for pH test pen:
This test pen is calibrated at the factory and can be used directly. The following conditions must be recalibrated:
Used (or placed) for a long time after calibration;
The electrodes are used frequently;
Measurement accuracy requirements are relatively high;
Do not reuse calibration buffer when making corrections;
When the pen has white crystals, this is normal. Do not be nervous. Soak it in water for a while;
Drop a few drops of the preservation solution or calibration buffer inside the pen holder. Do not use distilled water or pure water to soak or save the test pen;
There may be small bubbles in the sensitive bulb of the test glass electrode, which will affect the normal measurement of the electrode. When using, the electrode should be shaken to make the bubble run out of the sensitive bulb;
The glass electrode is easy to break, so be careful when using it;
If the displayed value is blurred or not displayed or the displayed value is much higher or lower than the true PH value of the solution , the battery should be replaced;
2) How to replace the battery:
Black pen top plate of a switch, and gently pull it out, do not pull off lines, can be seen four 1.5V batteries, replacement can be drawn;
Pay attention to battery polarity and select the same type of battery;
When the electrode is inserted into the test solution or calibration buffer, the maximum height indicated on the test pen should not be exceeded.
When the electrode is placed a long time, and a sensitive bulb exposed to the air, drying by the electrode, so that the display is unstable and slow response time, should be activated electrodes immersed in distilled water for several hours.;
To improve performance, at least once a week PH meter electrode into distilled water, every few minutes;
Protein precipitates (e.g., measuring milk \ cheese, etc.) to be immersed in a solution of hydrochloric acid and pepsin treated to eliminate; This solution is ready for use before, after use, the electrode was immersed in this solution for several hours, and then rinse with water , then immersed in distilled water for several hours ;
The grease film also affects the measurement of sensitive bulbs . Li removes the film , rinses the sensitive bulb with 75% alcohol solution , then wipes it with filter paper , rinses with water , and then immerses it in distilled water for several hours ;
2) pH calibration
Immerse the test pen electrode in a mixed phosphate standard buffer with a pH of 6.86 (at 25 ° C ) and shake gently;
Adjust the calibration potentiometer with a small screwdriver until the displayed value matches the pH of the standard buffer solution at ambient temperature ;
The electrode is inserted into potassium hydrogen phosphate dihydrogen phosphate of pH 4.01 or a standard buffer solution of borax of pH 9.18 ;
The displayed value should be within the tolerance of the error compared to the pH of the buffer solution .
-. Operation steps and methods
Remove the protective cover;
First wash the electrode of the pH meter with distilled water , and use the filter paper to absorb the moisture attached to the electrode;
Switch on the switch located on the battery compartment;
Insert the pH meter electrode into the liquid to be tested until the liquid is immersed slightly below the “ immersion line †. If conditions permit, the solution can be immersed slightly above the “ immersion line †;
Gently stir the solution until the value is stable, and read the displayed value;
After use, clean the electrode, turn off the switch, and put on the protective cover;
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