This method and apparatus is directed to measuring flow velocity of a flowing solid or fluid in a pipe. In the preferred and illustrated embodiment, a single magnet is utilized to impress a magnetic field on the flow, the field having a gradient. A concentrically arranged detection coil is positioned in the field and is connected with a nuclear magnetic resonance (NMR) or electron magnetic resonance (EMR) detection apparatus. A segment of the material moves through the magnetic field. The frequency of a the magnetic resonance signal emitted by the nuclei or electron changes proportionate to field intensity. In a fixed gradient, the time rate of change of the emitted NMR or EMR frequency signal is a linear function of flow velocity. This apparatus provides a measure of flow velocity by interrogating with pulses thereby obtaining a frequency dependent signal. The approach has the advantage of utilization of a single coil and yields measurements which are independent of density or filling factor and also independent of elemental couplings identified as T.sub.1 and T.sub.2.
James D. King;Erroll S. Riewerts