Micro-flow facility for traceability in steady and pulsating flow

Liquid low-flow calibration rig using syringe pump and weighing tank system

“…Several approaches can be used to reduce the evaporation effect, including trapping evaporation with a saturated vapor atmosphere [4,5] and applying a cover layer of a lowerdensity liquid [6,7], such as oil, which has a low vapor pressure. Evaporation trapping was applied to the present calibration rig to ensure the exchangeability of the working liquid.…”

“…Dynamic weighing methods have been adopted in many ultralow-flow calibration facilities [5][6][7]. The flow impact effect on the weighing scale might be a significant error source for the higher flow rates in the target flow rate range.…”

“…However, commercial syringe pumps are still being improved with regard to flow stability to eliminate unpredictable flow fluctuations [5]. Takamoto et al [14] developed a volumetric flow generator combined with a gravimetric standard as a calibration rig for use at low flow rates.…”

Optofluidic flow meter for sub-nanoliter per minute flow measurements

“…9 Briefly, the measurement principle of dynamic gravimetric methods for the standard is based on transferring the mass into a reservoir on the microbalance (Res2) during the measurement time interval. The flow equations and guiding uncertainties of a gravimetric measurement system are described in more detail in fundamental studies by Melvad (2010), 19 Bissig (2015), 20 and Wright and Schmidt (2015, 2019). 9 , 21 Similarly, we describe the governing equations for volumetric flow and measurement uncertainty for our design as where ( ) is the liquid mass flow through the system from Res1 into Res2, is the the flow rate uncertainty, and is the uncertainty in the device resistance.…”

“…Low-flow measurements break down when mass accumulation rates are on the same order as errors due to evaporation or external forces on the microbalance, such as from capillary forces against tubing. 9 , 10 In addition, as bulk fluid flow becomes smaller, competition with factors such as diffusion often blurs the resolution of ever-smaller flow displacements. 11 These factors add up to significant increases in relative measurement uncertainties below .…”