Magnetic Field‐Tracking Nuclear Resonance Gaussmeter

A feedback system is described by means of which a marginal oscillator may be referenced to the frequency of a nuclear resonance occurring in a magnetic field, and is thus useful as a magnetic field tracking nuclear resonance gaussmeter. An instrument is described which uses the proton resonance in water to track fields in the vicinity of 3500 G. The tracking range of the oscillator is 2 Mc about a center frequency of 14.5 Mc with an estimated tracking error of ±5 cps over this range at low tracking speed. A tracking rate as high as 50 kc/sec2 is possible with a tracking error of about 20 cps. A digital‐to‐analog conversion of the oscillator frequency has been used to present EPR spectra on an x axis linear in magnetic field, thus compensating for poor magnetic field regulation.