Patent ID: 7378845

Claim:
A method for measuring fluid flow rates comprising the steps of: (a) creating a non-oscillating magnetic field of a predetermined field strength across a flowing fluid, the fluid having a sufficiently high flow rate such that the time nuclei in the fluid spend being polarized by the non-oscillating magnetic field is proportional to the flow rate; (b) repeatedly performing the sub-steps of: (i) exposing the flowing fluid to an oscillating magnetic field pulse orthogonal to the non-oscillating magnetic field to generate an NMR signal, and (ii) using a detection coil to detect the NMR signal from the flowing fluid in the form of a free induction decay, a delay being applied between each repetition of sub-steps (i) and (ii), which delay is sufficient to allow substantially all the fluid exposed to the previous pulse to exit the detection coil before the next pulse is applied; (c) measuring initial magnitudes of the free induction decays; and (d) determining the fluid flow rate from the measured initial magnitudes, the measured initial magnitudes being inversely proportional to the flow rate.