PH as a routine water quality measuring instruments are widely used in industry, agriculture and environmental protection, for the use of all kinds of methods of pH, various manufacturers have different specifications and definitions, but there are some general rules is permanent. These rules include:
PH calibration must be on time. The first point must be neutral calibration solution, such as: pH6.86 or 7.
For acidic samples, second point need to use pH4.00 standard buffer calibration; for alkaline samples, second points need to use pH9.18 or 10.01 standard buffer.
The temperature compensation function of the instrument must be enabled when pH measurement is carried out. Usually, the sample temperature varies from 5 to C, and the pH value will increase or decrease from 0.01 to 0.05pH.
At present, the market is full of pH, the performance is different, the use of pH meter is also different. This article will summarize the use of various pH meters according to the type of pH meter for reference only.
Using method of knob type pH meter:
This kind of pH meter is composed of analog circuits, developed in the 60s of last century, it is characterized by calibration need to adjust the knob or use a screwdriver to adjust the built-in potentiometer. The advantage is that the performance is stable, the disadvantage is that the calibration is very tedious and the human error is large.
How to calibrate the knob type pH meter:
1. first of all, you need to use a thermometer to measure the temperature of the standard buffer, and then adjust the temperature knob of the instrument to the corresponding scale.
2. immerse the pH electrode in pH6.86 (or 7) standard buffer, and find the pH value of the standard buffer at the current temperature.
For example, at 25 degrees C, the standard value of pH6.86 standard buffer is 6.86pH, and that of 6.92pH is 10 at C.
3. adjust the instrument "positioning" knob until the screen displays the corresponding standard value.
4. rinse the pH electrode with distilled water, and then immerse the electrode in the next standard buffer (e.g. pH4.00).
5. adjust the "slope" knob until the screen displays the current temperature of this standard buffer pH value (for example: 10 degrees C, the standard value of pH4.00 is 3.99pH).
6. wash the pH electrode again and immerse in pH6.86 (or 7) standard buffer. If the display value and standard value are deviation, then adjust the "positioning" knob again.
7. clean the pH electrode and retest the standard buffer used at second points. If the deviation occurs, adjust the "slope" knob again.
8. repeat the verification according to the above method and adjust the instrument until the calibration value is completely accurate.