![]() ![]() Repeatability is an indication of precision. In the United States, this would ultimately be to NIST standards, through the National Voluntary Laboratory Accreditation Program, known as NVLAP. The International Vocabulary of Metrology (VIM) defines traceability as the “property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.” Basically, the flow meter’s performance must be traceable back to a known documented standard. If the assumption of proper calibration is wrong, inaccurate flow readings, process issues, or regulatory violations may result.įactors that ensure flow meter calibration meets ISO/IEC standards include: Traceability Meter accuracy is only as good as the quality of its calibration. When a meter is calibrated, there’s an assumption that all factors were input correctly and properly compared to a known standard. Additional input adds more uncertainty - piping configuration, friction, water temperature, and other factors.Īn uncalibrated meter will produce flow readings with greater than acceptable inaccuracy. Without calibration, flow measurement relies only on an algorithm, such as a flow coefficient for the meter. Calibration laboratories must meet the requirements of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Most often, standards include those of the National Institute of Standards and Technology (NIST). They require and fully expect the flow data to be accurate and reproducible.Ĭalibration is a comparison of a flow meter’s performance against a known standard. Utility managers and operators rely on flow meters to provide critical information for process monitoring and control. ![]()
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