| What is accuracy of a mass flow meter, what is repeatability of a mass flow meter, and what difference does the difference make?
First let’s define the terms. Accuracy of a mass flow meter is the expression of error (%) as compared to a primary standard. In practical terms it is the degree to which the actual output of the flow meter matches the calibration curve of the flow meter. Repeatability of a mass flow meter is the amount (%) that any single device can repeat the value previously delivered at the same conditions. In practical terms this means that the output seen at a given set of conditions may, or may not, match the calibration curve of the instrument but it will regularly be the output seen at that same set of conditions. A highly accurate instrument requires high repeatability, but a highly repeatable instrument does not require high accuracy. |
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So, why does it matter? Increasing accuracy tends to come at an increasing cost which can be justified if required in the application. High repeatability with lower accuracy may be a cost effective solution for a given application. Clearly identifying the requirements of an application will allow the best instrumentation recommendation to be made.
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