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6.3
Notes about pH Calibration
a)
Keeping the freshness and cleanliness of calibration buffers is essential for accurate pH
measurement. The small bottles of pH buffers come with the meter should be replaced within 3
months after opening. The new buffer solutions should be made by a legitimate lab supply
manufacturer. Avoid sunlight and air contact when the buffers are not being used, and store at
room temperature.
1)
This meter can adopt random 1-point, 2-point or 3-point automatic calibration. During calibration,
short press to return to measurement mode. When the measurement accuracy is ≤ ±0.1pH,
choose a buffer that’s close to the estimated measurement range and perform 1-point calibration
would be good. Choose pH 4.00 and pH 7.00 to calibrate if the measurement range is within the
acidity range (<pH 7) and choose pH 7.00 and pH 10.01 to calibrate if just within the alkalinity
range (>pH 7).
2)
Choose 3-point calibration to achieve a more accurate measurement if the measurement range
is wide, or if the electrode has not been used for long. When connecting a new pH electrode, it
must be calibrated at 3 points.
3)
The frequency that you need to calibrate your meter depends on the tested samples, condition of
electrodes, and the requirement of the accuracy. For high-accuracy measurements (≤ ±0.02pH),
the meter should be calibrated before test every time; For ordinary-accuracy measurements
(≥±0.1pH), once calibrated, the meter can be used for about a week or longer. In the following
cases, the meter must be re-calibrated:
•
The electrode hasn’t been used for a long time or a new electrode is connected.
•
After measuring strong acid (pH<2) or strong base (pH>12) solutions.
•
After measuring fluoride-containing solution and strong organic solution.
•
There is a significant temperature difference between the test sample and the buffer solution.
6.4
Sample Test
Power on the meter. Connect the pH electrode and the meter goes to pH measurement mode
automatically. Screw off the KCL storage bottle. Rinse the electrode with pure water. Shake off excess
water or blot-dry with clean tissue or kimwipe. Stir the electrode for a few seconds after it’s dipped into
the sample solution and then hold it still. Wait for the reading to get fully stabilized ( appears and
stays). Then save the measurement by pressing .
According to the pH isothermal measurement principle, the closer the test sample’s temperature is to the