A flow measurement assembly includes a coupler and a flow channel (40). The coupler maintains a magnet (54) and a sensor (58) spaced from the magnet. The flow channel is positionable between the magnet and the sensor. The flow channel includes a housing having an inlet (42), an outlet (44) spaced from the inlet, and a flow conduit (56) fluidly open to the inlet and the outlet. A ferrous body (58) is movably disposed in the conduit. The sensor is configured to detect a frequency of a change within a magnetic field as the ferrous body travels within the flow conduit between the magnet and the sensor.
