Force-free and contactless electromagnetic flow rate sensors

We present a novel design of flowmeter using a single cylindrical permanent magnet magnetized perpendicularly to its axis about which it can freely rotate, and placed close the duct with liquid metal flow. The electromagetic torque on the magnet caused by the liquid metal flow sets the magnet into rotation. However, the equilibrium rotation rate, which attained at vanishing net electromagnetic torque on the magnet, depends only on the flowrate and geometry of the system while it is independent of the electromagnetic torque itself. A laboratory model of a such flowmeter has been built and tested at a liquid metal flow.