Abstract
Following the miniaturisation of fluidic components, the demand for traceable measurements of micro and nanoflows is increasing in various technological fields such as pharmaceuticals, biotechnology and automotive industry. Gravimetric flow measurement methods are accurate at microflows and above, but have a lower limit of about 5nLmin−1. Several alternative approaches have been developed to circumvent this limit. Here a measurement setup and proof of principle is presented for a method measuring the gas flows generated by complete evaporation of liquid ethanol nanoflows. The gas flow measurement is based on the well-established method of determining the pressure drop across a geometrically precisely defined circular opening in the molecular flow regime. Liquid flow rates from a syringe pump in the range of 5nLmin−1 to 200nLmin−1 are measured with an expanded uncertainty as low as 340pLmin−1 at instantaneous flow rates. Strategies to further improve accuracy are discussed.
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