Traceability of dynamic magnetic fields by NMR magnetometry

A method to provide traceability with low uncertainties for magnetic alternating fields is presented. The reconstruction of an AC field waveform is performed by the measurement of the NMR pulses time position obtained by the superposition of a static magnetic field to the AC magnetic field. A frequency sweep in the excitation of the NMR probe allows the changing of the pulses positions covering all the AC waveform. As the frequency at which the NMR pulse exists is related only to the proton gyromagnetic ratio, it can be considered as a primary standard. A prototype tested experimentally shows the feasibility of the method proposed.