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Reproducibility of Liquid Micro-Flow Measurements



John D. Wright, James W. Schmidt


New applications in biology, medicine, and manufacturing require reliable measurements of liquid flows smaller than 100 υL/min. NIST addressed this requirement by improving the reliability and ease of use of NIST’s Dynamic Gravimetric Micro-Flow Standard. The meter under test is now connected to the weighing beaker by a liquid bridge that reduces variations in parasitic surface tension forces as the level of liquid in the collection beaker rises. We describe other improvements to NIST’s standard (e.g. pipette positioning and evaporation reduction) and provide an uncertainty analysis for the present system. The gravimetric standard measures liquid flow between 0.1 υL/min and 100 υL/min with uncertainty ranging from 4.5 % to 0.04 %. Repeated calibrations of five commercially available micro-flow meters (one for nearly 2 years) show that their calibrations are reproducible within 1.5 % for many months.
Proceedings Title
Conference Dates
June 26-28, 2019
Conference Location


micro-flow, flow meter, primary standard, uncertainty


Wright, J. and Schmidt, J. (2019), Reproducibility of Liquid Micro-Flow Measurements, FLOMEKO 2019, Lisbon, -1, [online], (Accessed May 24, 2024)


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Created June 26, 2019, Updated November 18, 2019