An NMR marginal oscillator for measuring magnetic fields below 50 mT

A marginal oscillator, developed to measure or control magnetic fields in the flux-density range from 50 mT down to 1 mT by using nuclear magnetic resonance (NMR), is described. This provides additional signal-dependent modulation of the feedback conductance, considerably increasing the signal-to-noise ratio. Observing proton resonance in an aqueous CuSO/sub 4/ solution, a sample volume of about 2 cm/sup 3/ has led to a signal-to-noise ratio of 50 dB obtained in a field with a flux density of 15 mT.<
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