Grade of Precision pH Meters and Accuracy of pH Instruments
The level of precision pH meter and the accuracy of pH instrument The level of instruments and their accuracy are not completely consistent. The level of an acidity meter is represented by the division value (resolution or small display value) of its indicator (abbreviated as an electric meter). For example, an instrument with a division of 0.1 pH is called a 0.1 level instrument; Instruments with a small display value of 0.001PH are called 0.001 level instruments, and so on. The accuracy of the instrument is the comprehensive error of the standard solution tested by the electrode and the electrode, which is not only related to the electrode, but also to the glass electrode and reference electrode. Starting from practical usage requirements, the current division value of the electric meter is 0.1-0.001PH. If necessary, with the current level of technology, more precise electric meters can be made. However, due to structural and manufacturing reasons, the performance of commonly used electrodes currently cannot reach a completely ideal level. The repeatability error of the glass electrode and the stability of the solution interface potential of the reference electrode are both not better than 0.01 pH.
Therefore, no matter how high the resolution of the electric meter is, the accuracy of instrument testing cannot be better than 0.01pH. However, choosing high-resolution instruments can greatly overcome or eliminate the influence of the electric meter on testing errors. Due to the fact that achieving satisfactory accuracy in electric meters is no longer a problem, efforts are being made to continuously improve the intelligence, humanization, reliability, ease of operation, and cost-effectiveness of instruments. The pHS-3C+and other "+" series instruments produced by our company reflect this trend. The relationship between the level of acidity meter and its testing accuracy is specified in the National Metrological Verification Regulations for Acidity Meters (JJG119-84) as follows:
The level of the instrument is 0.2, 0.1, 0.02, 0.01, and 0.001
Dividing value or small display value (pH) 0.2 0.1 0.02 0.01 0.001
Meter reading error (pH) ± 0.1 ± 0.05 ± 0.01 ± 0.01 ± 0.002
The total error of the accompanying test indication (pH) is ± 0.2 ± 0.1 ± 0.02 ± 0.02 ± 0.01
