MAGNETIC NUCLEAR RESONANCE

A differential amplifier is connected to the coils. A precise trim of the of the two injections voltages (VINJ) is used to cancel them. Only the voltages due to the protonic precession are detected.
The output voltage is re-injected through a potentiometer as an excitation voltage at the Larmor frequency to induce the magnetic resonance. The system constitute an oscillator allowing a continuous wave output with a frequency proportional to the observed magnetic field.