ec_measurement_errors
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ec_measurement_errors [07/11/2014 14:30] pieter [Conductivity Accuracy] |
ec_measurement_errors [31/03/2015 07:37] pieter |
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| ====== EC Measurement Errors ====== | ====== EC Measurement Errors ====== | ||
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| The standards that are used for the calibration are the largest cause of error which cannot be eliminated. The solutions have mostly an accuracy of 1% or 0.5%. This needs to be checked with the supplier or manufacturer of the solutions. | The standards that are used for the calibration are the largest cause of error which cannot be eliminated. The solutions have mostly an accuracy of 1% or 0.5%. This needs to be checked with the supplier or manufacturer of the solutions. | ||
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| - | ===== Temperature compensation ===== | ||
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| - | A Conductivity meter can reflect the absolute conductivity (i.e. not temperature compensated) or the relative conductivity which is the recalculated absolute measurement towards the reference temperature. To obtain the relative value, the meter is using a certain temperature dependent method to convert the absolute measurement. The Consort meters make use of the international standard **EN27888** to do so. This temperature compensation assumes the measured value is behaving as a **natural water**. The measured products mostly have another temperature behaviour. This leads to calculation differences, | ||
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| - | e.g. | ||
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| - | Many people notice another value than expected immediately after calibration in a KCl solution. When the temperature is 22°C in a 0.01 M KCl solution, the meter will show in this same solution //1421 µS/cm// while //1413 µS/cm// is expected at a reference temperature of 25°C. This is hardly noticed when the calibration is done at or close to the reference temperature. | ||
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| * Allow the electrodes sufficient time to stabilise while calibrating or measuring. A stability indicator on most of our meters prompts the user when readings should be taken. | * Allow the electrodes sufficient time to stabilise while calibrating or measuring. A stability indicator on most of our meters prompts the user when readings should be taken. | ||
| These measurement practices allow to keep the errors low, error due to contaminations of the solutions, temperature differences or not taking enough time. | These measurement practices allow to keep the errors low, error due to contaminations of the solutions, temperature differences or not taking enough time. | ||
| + | ---- | ||
| + | ===== Temperature compensation ===== | ||
| + | Many people notice another value than expected immediately after calibration in a KCl solution. Here is explained why. | ||
| + | A Conductivity meter can reflect the absolute conductivity (i.e. not temperature compensated) or the relative conductivity which is the recalculated absolute measurement towards the reference temperature. To obtain the relative value, the meter is using a certain temperature dependent method to convert the absolute measurement. The Consort meters make use of the general accepted international standard **EN 27888** to do so. This temperature compensation assumes the measured value is behaving as a **natural water**. The measured products mostly have another temperature behaviour. This leads to calculation differences, | ||
| + | |||
| + | e.g. | ||
| + | |||
| + | When the temperature is 22°C in a 0.01 M KCl solution, the meter will show in this same solution //1421 µS/cm// while //1413 µS/cm// is expected at a reference temperature of 25°C. This is hardly noticed when the calibration is done at or close to the reference temperature. | ||
| + | ---- | ||
ec_measurement_errors.txt · Last modified: 31/03/2015 09:54 by pieter
