Greatly Improved Small Inductance Measurement Using Quartz Crystal Parasitic Capacitance Compensation

Generally, quartz crystal inductance frequency pulling in oscillators is very low and therefore is not often used in practice. The new method of improving frequency pullability uses inductance to compensate for quartz stray capacitances. To this end, a special AT fundamental quartz crystal working near the antiresonance frequency is selected. By modifying its equivalent circuit with load inductance and series tuning capacitance, the magnetic sensing of the circuit can be highly improved. The experimental results show that the new approach using the quartz crystal stray capacitance compensation method increases the frequency pulling range (from ≅2 kHz/μH to ≅600 kHz/μH) by ×300 depending on the type of oscillator, making possible the measurement of nano-magnetic changes.