When do pH meters need to use temperature compensation
When doing pH measurement with general accuracy, temperature compensation can be used when the temperature of the sample solution is different from that of the standard solution.
However, when doing high-precision measurement, try not to use automatic temperature compensation. Instead, you need to look up the table after the measurement to find the pH value of the solution at 25 °C, or wait until the solution reaches 25 °C before measuring.
Many pH meters now have automatic temperature compensation function. When automatic temperature compensation is used, the instrument converts the conversion coefficient obtained by the electrode at the calibrated temperature to the conversion coefficient at the actual temperature according to the Nernst formula, so as to obtain the pH at the actual temperature. value.
Instruments without automatic temperature compensation function need to perform temperature compensation manually. In the case of low accuracy requirements, this operation is possible.
In fact, whether it is manual temperature compensation or automatic temperature compensation, it is not very sufficient. According to the operational definition of pH meter measurement, in order to obtain accurate measurement results, the sample solution and the standard solution should be measured at the same and constant temperature, which is the principle of isothermal measurement.
In order to reduce the temperature-to-pH measurement error, we should try to choose a standard buffer solution that is close to the pH value of the measured solution, and try to make the temperature of the calibration solution consistent with or close to the temperature of the measured solution.
