How to distinguish the level and accuracy of an acidity meter
The level of a pH meter is represented by the resolution or minimum display value of its indicator (abbreviated as an electrometer). For example, an instrument with a resolution of 0.1 pH is called a 0.1 level instrument; An instrument with a minimum display value of 0.001 pH is called a 0.001 level instrument. The accuracy of the instrument is the comprehensive error of the standard solution tested by the electric meter and electrode, which is not only related to the electric meter, but also to the glass electrode and reference electrode.
However, due to structural and manufacturing reasons, the performance of commonly used electrodes cannot yet reach a completely ideal level. The repeatability error of the glass electrode and the stability of the solution junction potential of the reference electrode are not better than 0.01 pH. Therefore, no matter how high the resolution of the electrometer is, the accuracy of instrument testing is difficult to exceed 0.01 pH. However, choosing high-resolution instruments can minimize or eliminate the impact of electrical meters on testing errors. It is no longer a problem to achieve satisfactory accuracy for the electric meter, so currently, there is continuous safety and improvement in the intelligence, humanization, reliability, easy operation, and cost-effectiveness of the instrument.
It should also be noted that why is the testing range specified for the total error of instrument indication from pH 3 to pH 10? It is because the liquid interface potential of the reference electrode is related to the pH of the solution. Within the range of pH 3 to pH 10, the liquid interface potential can be stable within the range of ± 0.01pH. If 10<pH<3, the error caused by the liquid interface potential can be as high as ± 0.07pH. At the same time, glass electrodes can also produce alkali and acid errors in alkaline and acidic solutions. Therefore, it is necessary to specify the detection within the range of pH 3 to pH 10, otherwise it will be impossible to distinguish the total reading error of various levels of acidity meters.
In summary, the level of pH meter and the accuracy of the instrument are two different concepts, and the level of the instrument is not entirely consistent with its accuracy. However, based on practical usage requirements, the current division value of the electric meter is between 0.1 and 0.001 pH. If necessary, with the current level of technology, more precise electric meters can be produced.
