A sensitive displacement transducer using an extremely reentrant 84 MHz cavity oscillator

Abstract

A single-turn toroidal optimization of the inductor in the LC circuit of a capacitive displacement transducer is described. It has a higher Q than the usual multiturn coil and allows the construction of a rigid LC resonator which does not use any insulators. When this resonator is used in conjunction with a tunnel diode oscillator, the sensitivity of the capacitor to position changes is conservatively estimated as 7×10−12 cm.