What is automatic calibration of a pH meter?
What is automatic calibration of a pH meter?
pH meter is automatically calibrated and can only be applied to microcomputer or computer chip pH meters. This type of pH meter has input various buffer solution data and operating procedures into the chip, so there is no need to check the pHs of the buffer solution. If there is a temperature sensor, there is no need to adjust the temperature value. You only need to select one-point calibration, two-point calibration or three-point extreme accuracy according to the test accuracy of the sample solution (press the CAL key once, twice or three times), and the instrument will automatically display the calibration. end symbol. Three-point calibration is a feature of this type of pH meter. It is divided into calibrated pH7.00 (or pH6.86), pH4.00 or pH10.0l (or pH9.18)
Three points, the test is more accurate across the entire pH range. When using this type of instrument, be sure to check the specific types of the three pH buffer solutions built into the pH meter, such as pH 6.86 or pH 7.00, pH 9.18 or pH 10.01, and choose the correct buffer. solution. Some computer-based pH meters can set the pH buffer solution by themselves, but the settings must be correct in advance, otherwise the computer will not be able to recognize two similar buffer solutions and calibration errors will occur. Computer-based pH meters will make calibration more convenient.
Can temperature compensation eliminate all temperature-induced errors in pH meters?
Can temperature compensation eliminate all errors caused by temperature in the pH meter? It must be particularly pointed out that the temperature compensation set on the pH meter only compensates for the slope term of the electrode (2.303RT/F). Also affected by temperature are the glass electrode standard potential, reference electrode potential, liquid junction potential, etc., which do not have a strict linear relationship with temperature. At the same time, the PH electrode also takes a certain amount of time to reach equilibrium at the new temperature. Therefore, neither manual temperature compensation nor automatic temperature compensation is sufficient. According to the operational definition of pH measurement, in order to obtain precise measurement results, the sample solution and the standard solution should be measured at the same and constant temperature. This is the principle of isothermal measurement. For pH measurements with general accuracy requirements, temperature compensation can be used when the temperatures of the sample solution and the standard solution are different.
