The Hall flowmeter is a calibrated device built to measure the flow rate of metal powders. It consists of a stand and two funnels with accurately machined and tapered apertures. The device is approximately 30 cm tall while the funnels have an outside diameter of 7.5 cm. Standardized aperture diameters are 2.5 and 5 mm. The bottom view of the two funnels is shown in the right-most photograph. The inside surface of the aluminum funnels are highly polished. The flow rate is determined by the time for a 50 g sample to flow through the aperture.
The device can also be used to measure the “apparent density” of free-flowing powders by measuring the time for material flowing through the 2.5 mm aperture to fill a standardized 25 cm3 container placed below the aperture. The bottom of the density cup can be seen in the second and third photographs. The cup in this particular unit was constructed out of copper.
The 5 mm aperture funnel is used to measure the “apparent density” for non free-flowing powders.
“Apparent density” is defined as the mass per unit volume.
