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How much does temperature affect the measurement accuracy of a pH meter?

by:BOQU     2023-03-26
Many people have mentioned the relationship between temperature and pH. For pH electricity, the effect of temperature is 0.003pH/℃ for each pH. If a 0.2-grade pH meter is calibrated in a pH7.00 buffer solution, then the tested solution (if the pH range of the solution is between pH6~8 There is a difference of one pH unit from pH7.00), then the maximum error caused by temperature is 30×0.003=0.09pH. If it is 3 pH units (in the range of pH4~10), the maximum error is 0.27pH, from which it can be seen that the temperature has a great influence on pH. Of course, we can also draw conclusions from it. In order to reduce the error of temperature to pH measurement, we should pay attention to the following three points: (a) Try to choose a buffer solution close to the pH value of the measured solution to calibrate the pH meter. (b) Try to make the temperature of the calibration solution consistent with or close to the temperature of the measured solution. (c) A pH meter with temperature compensation should be selected. pH meters with an accuracy higher than 0.1pH have temperature compensation adjustments, while pH meters with a grade of 0.2 do not have temperature compensation. Some 0.2-grade pH meters also claim to have 0.1-grade accuracy. In fact, this is impossible. Some people confuse the two concepts of resolution 0.1pH and precision 0.1pH. Even in terms of one pH unit, the pH error at a distance of 60°C is 0.003×60=0.18pH. Therefore, the high accuracy of a pH meter without temperature compensation is only 0.2pH.
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