Although many types of pH meters are used, the calibration method uses a two-point calibration method that selects two standard buffers: one is pH7 standard buffer and the second is pH9 standard buffer or pH4 standard buffer.
First use pH7 standard buffer to locate the electrometer, and then select the second standard buffer according to the pH value of the solution to be tested. If the test solution is acidic, the choice of pH4 standard buffer; if the test solution was alkaline, the choice of pH9 standard buffer. In the case of a manually adjusted pH meter, several times between two standard buffers should be repeated until the Zero and Positioning (Slope) knobs are not adjusted and the pH meter accurately shows the pH of both standard buffers. The calibration process is completed.
After that, the zero and positioning knobs should not be moved during the measurement. If the intelligent pH meter, then do not need to repeatedly adjust, because of its internal storage of several standard pH buffer to choose from, and can automatically identify and automatically calibrate. But pay attention to the standard buffer selection and the accuracy of its preparation. The intelligent 0.01-level pH meter generally has three to five kinds of standard buffer pH values, such as Kohler's KL-016 pH meter.
Second, pay special attention to the temperature of the solution to be measured before calibration. So that you can select the standard buffer correctly and adjust the temperature compensation knob on the electrometer panel to match the temperature of the solution under test. Different temperatures, the standard buffer solution pH is not the same.