Inductive transducer for displacement-to-frequency conversion

A controllable three-frequency oscillator is usable as a displacement-frequency converter. Controlling such an oscillator is possible by means of nondifferential, parametric displacement transducer whose inductance forms part of the tank circuit of a tunable first amplifier (frequency F sub 10), a mixer, a tuned second amplifier (frequency F sub 20), and another mixer whose output is connected directly back to the input of the first amplifier. The other inputs of both mixers are connected to and receive signals from a quartz oscillator (frequency F sub 3). With the transducer inductance set within the middle of its range, the converter is adjusted so that F sub 10 + F sub 20 is approximately equal to F sub 3. When both amplifiers have sufficient gain to satisfy the condition of amplitude balance, then self-excited oscillations occur in the converter with frequencies F sub 1 at the output of the first amplifier and F sub 2 at the output of the second amplifier, F sub 1 + F sub 2 = F sub 3. A transducer which ensures a frequency-displacement characteristic F sub 10 (0) such that, where both frequencies F sub 1 and F sub 2 as well as thier difference are linear functions of the displacement o, was designed. The transdcuer is connected into the tank circuit of the first (transistor) amplifier. The nonlinearity of its inductance-displacement characteristic is variable.