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The level and accuracy of PH acidity meter are two different concepts

by:BOQU     2023-04-14
The level of pH meter and the accuracy of the instrument are two different concepts, and the level of the instrument is not completely consistent with its accuracy. The level of the acidity meter is expressed according to the division value (resolution or small display value) of its indicator (referred to as the electric meter), for example: an instrument with a division of 0.1pH is called a 0.1-level instrument; the small display value is 0.001pH The instruments are called class 0.001 instruments, and so on. The accuracy of the instrument is the comprehensive error of the electrometer and the electrode matching test standard solution, which is not only related to the electrometer, but also more related to the glass electrode and the reference electrode. Starting from the actual use requirements, the division value of the electric meter is 0.1~0.001pH. If necessary, a more precise electric meter can be produced according to the current technological level. However, due to structural and manufacturing reasons, the performance of commonly used electrodes cannot reach a completely ideal level. Neither the repeatability error of the glass electrode nor the stability of the solution junction potential of the reference electrode is better than 0.01pH. Therefore, no matter how high the resolution of the electrometer is, the test accuracy of the instrument is difficult to be better than 0.01pH. However, choosing a high-resolution instrument can overcome the influence of the electric meter on the test error to the greatest extent. Since it is not a problem to make the electric meter achieve satisfactory accuracy, it is constantly innovating and improving in terms of intelligence, humanization, reliability, easy operation and cost performance of the instrument. The relationship between the grade of the acidity meter and its test accuracy is stipulated in the measurement and verification regulations of the pH meter (JJG119-84) as follows: The grade of the pH meter instrument is 0.2, 0.1, 0.02, 0.01, 0.001. Display value (pH) 0.2, 0.1, 0.02, 0.01, 0.001 Electric meter indication error (pH) ±0.1, ±0.05, ±0.01, ±0.01, ±0.002 Supporting test indication total error (pH) ±0.2, ±0.1 . When there is a change; after measuring PH> 12 or PH < 2; after measuring the solution containing fluoride and the acidity is in the solution of PH < 7 or a concentrated organic solution.
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