ph_accuracy
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ph_accuracy [27/02/2019 07:31] pieter [The pH meter] |
ph_accuracy [27/02/2019 07:36] pieter [The pH buffers] |
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| ==== The pH meter ==== | ==== The pH meter ==== | ||
| - | A good qualitative meter is the smallest error introduced in the pH measurement system. The error of the device is to be seen as relative to the nearest calibration points. It depends on the reproducibility | + | A good qualitative meter is the smallest error introduced in the pH measurement system. The error of the device is to be seen as relative to the nearest calibration points. It depends on: |
| + | * the __reproducibility__ | ||
| + | * the measurement | ||
| As example, a pH meter with an accuracy given as (0.2%+1 digit) and a resolution of 0.01 pH. It depends on the reproducibility at the calibration points (± 0.01, 1 digit) and the linearity between and outside the calibration points (0.2%). When a calibration is done at pH 7.00 and pH 4.00, the device error at these same points is ±0.01 pH. For a measurement at 5.50 pH , the device error is (1.50 pH * 0.002) ± 0.01. | As example, a pH meter with an accuracy given as (0.2%+1 digit) and a resolution of 0.01 pH. It depends on the reproducibility at the calibration points (± 0.01, 1 digit) and the linearity between and outside the calibration points (0.2%). When a calibration is done at pH 7.00 and pH 4.00, the device error at these same points is ±0.01 pH. For a measurement at 5.50 pH , the device error is (1.50 pH * 0.002) ± 0.01. | ||
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| ==== The pH buffers ==== | ==== The pH buffers ==== | ||
| - | It is advised to calibrate the meter with electrode using buffers that cover or are near to the measurements to be performed and/or to be acquired. Use at least 2 buffers or more when measuring in a larger pH range. | + | It is advised to calibrate the meter with the electrode using buffers that cover or are near to the measurements to be performed and/or to be acquired. Use at least 2 buffers or more when measuring in a larger pH range. |
| Check the accuracy of the pH buffers to know the possible measurement errors. Measuring between 2 buffers, used for the calibration, | Check the accuracy of the pH buffers to know the possible measurement errors. Measuring between 2 buffers, used for the calibration, | ||
ph_accuracy.txt · Last modified: 13/03/2019 09:59 by pieter
