Abstract: A valve unit for a flowing medium is combined with an electrical measuring system to provide measurement of the rate of flow of the medium. The valve unit is connected to a propeller-type rotor disposed in a conduit which communicates with the valve. The rotor incorporates a permanent magnet in at least one vane thereof and the measuring system includes a magnetic pulse generator which senses the magnetic field produced by the magnet and generates a corresponding train of pulses during the rotation of the rotor. An amplifier-differentiator connected to the pulse generator produces an output in accordance with the derivative of the pulses so as to provide an indication of the rate of flow.