Digital pH meter PH value measurement

I. Preparation 1. The instrument should be placed flat on a workbench that conforms to the environment of use, and the stand should be erected at a visual angle.

2. Positioning measurement method of pH value:

(I) Two-point positioning method (high-precision measurement method)

(1) Connect the electrode wire, and move the reference electrode and the PH electrode that has been fully activated for more than 24h into the first standard buffer pH1 (eg, pH1=4.00). After the instrument response is stable, adjust the positioning knob to display on the instrument as " 0.00";

(2) Remove the electrical grade system from the first standard solution, rinse with deionized water, and blot dry the electrical surface water on the filter paper and transfer it into the second standard solution (eg, pH2=9.18). The instrument response is stable. After that, adjust the slope knob so that the instrument displays (â–³pH=pH1-pH2=9.18-4.00=5.18) After that, the slope knob cannot be moved any longer unless the electrode system is changed;

(3) After the slope adjustment is completed, re-adjust the positioning knob so that the instrument displays the actual pH value of the second standard solution (9.18). At this point, the 2 point positioning is completed;

(4) The electrode is removed from the second standard solution, rinsed, blotted, and transferred into the solution to be tested. The value displayed after the instrument response is stable is the pH of the solution to be tested.

(b) One-point positioning method (rough measurement method)

(1) Adjust the temperature compensation knob to the solution temperature value;

(2) Turn the slope compensation knob to the left to the head;

(3) The electric level system is moved into the standard solution (a single point method uses only a standard solution, such as pH = 4.00), adjust the positioning knob so that the instrument displays "4.00";

(4) Take out the electric level, rinse and dry the moisture and move it to the solution to be tested. The value displayed after the instrument responds to stability is the pH value of the solution to be tested.

Second, the temperature measurement 1. The function selection dial to the temperature file.

2. Insert the temperature probe into the jack and place the temperature probe in ambient conditions or in a solution. After the instrument response is stable, the instrument display value is the ambient or solution temperature value.

Third, pay attention to matters 1. Make good preparations before using the instrument.

2. After the instrument is powered on or during the measurement process, unstable or skipping occurs. Check the power supply, such as voltage, warm-up time, and electrode system.

3. Use different electrodes should pay attention to exclude ion interference, choose a good salt bridge, if necessary, use ionic strength fixative.

4. Before the electrode system is removed from the first solution and transferred into the second solution, it must be cleaned with deionized water or double-distilled water, and the surface water should be dried with filter paper so as not to influence the accuracy of the measurement result.

5. The instrument should be stored in a dry, clean and non-corrosive place. After each measurement, the power should be turned off and the exit electrode and temperature probe should be properly stored. After cleaning the glass electrode, it can be immersed in deionized water to be used (note that the surface of the water must not be lower than the glass bulb). After the calomel electrode is cleaned, put on the rubber cap and store it in the matching box. When the calomel electrode is filled with liquid, it leaks or is not saturated. When the salt bridge is interrupted, the saturated liquid must be added in time.

6. This type of instrument uses large-scale integrated circuits and has a high input resistance. When any components are repaired and soldered inside the instrument, a soldering iron with a good grounding wire below 45W should be used. If there is no grounding wire, remove the power plug. welding.