pH meter maintenance and precautions

1) Maintenance of the pH test pen and precautions:

This test pen is factory calibrated and ready for use. The following conditions must be recalibrated:

Has been used (or placed) for a long time after calibration;

Electrodes are used frequently;

The measurement accuracy is relatively high;

Do not reuse calibration buffer when making calibrations;

When the pen has a white crystal, this is a normal phenomenon, please do not be nervous, soak for a while with fresh water;

Drop a few drops of storage solution or calibration buffer inside the pen holder. Do not use distilled or pure water to soak or preserve the test pen.

The test pen glass electrode sensitive bulb may have small air bubbles, which will affect the normal measurement of the electrode. When using, the electrode should be shaken to make the air bubble run out of the sensitive bulb;

The glass electrode is easy to break, so be careful when using it;

If the display value is fuzzy or not displayed or the displayed value is much higher or lower than the true pH of the solution, the battery should be replaced;

2) How to replace the battery:

Pull the black plate with the switch on the pen, gently pull it out, do not pull off the wire, you can see four 1.5V batteries, pull out and replace;

Pay attention to the battery polarity and select the same type of battery;

When the electrode is inserted into the test solution or calibration buffer, the maximum height marked on the test pen cannot be exceeded.

If the electrode is left for a long time and the sensitive bulb is exposed to air, the electrode becomes dry, which makes the response slow and the display value unstable. At this time, the electrode should be immersed in distilled water for several hours;

To improve performance, the pH meter electrode is inserted into distilled water at least once a week for a few minutes each time;

Protein precipitates (eg milk, cheese, etc.) should be immersed in pepsin and hydrochloric acid solution for elimination; this solution should be prepared before use and after use, the electrode should be immersed in this solution for several hours and then rinsed with water. , and then immersed in distilled water for several hours;

The grease film also affected the measurement of sensitive bulbs. Lee removed the film, washed sensitive bulbs with a 75% alcohol solution, wiped dry with filter paper, rinsed well with water, and immersed it in distilled water for several hours.

2) pH calibration The test pen electrode was immersed in a mixed phosphate standard buffer with a pH of 6.86 (at 25°C) and gently shaken;

Use a small screwdriver to adjust the potentiometer until the displayed value matches the pH of the standard buffer solution at ambient temperature;

The electrode was inserted into pH 4.01 of potassium phosphate monobasic or pH 9.18 in borax standard buffer;

The displayed value should be within the allowable error range compared to the pH of the buffer solution.

-. Operation steps and methods Remove the protective cover;

The electrode of the PH meter is first cleaned with distilled water, and the moisture attached to the electrode is dried with a filter paper;

Switch on the switch on the battery compartment;

Insert the electrode of PH meter into the liquid to be measured until the liquid is immersed slightly below the “immersion line”. If the 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;