RISE Test Facilities for the Measurement of Ultra-Low Flow Rates and Volumes with a Focus on Medical Applications

In the framework of the ongoing EMPIR JRP 18HLT08 Metrology for Drug Delivery (MeDDII),
a main task is to improve dosing accuracy and enable traceable measurements of volume, flow
and pressure of existing drug delivery devices and in-line sensors operating, in some cases, at ultralow
flow rates. This can be achieved by developing new calibration methods and by expanding
existing metrological infrastructure. The MeDDII project includes, among other issues, investigations
on fast changing flow rates, physical properties of liquid mixtures and occlusion phenomena
to avoid inaccurate measurement results and thus improve patient safety. This paper describes
the extension of an existing measurement facility at RISE and the design and construction of a new
measurement facility to be able to carry out such investigations. The new measurement facility,
which is based on the dynamic gravimetric method, is unique worldwide in respect of the lowest
measurable flow rate. The gravimetric measuring principle is pushed to the limits of what is feasible.
Here, the smallest changes in the ambient conditions have a large influence on the measurement
accuracy. The new infrastructure can be used to develop and validate novel calibration procedures
for existing drug delivery devices over a wide flow rate range. The extension of the measurement
facilities also enables inline measurement of the pressure and the dynamic viscosity of Newtonian
liquids. For this purpose, it is ensured that all measurements are traceable to primary standards.