Ultrasonic wave oscillator circuit with output meter

An ultrasonic wave oscillator circuit having an output meter circuit comprising:

• an oscillation system including a vibrator for generating a resonant frequency and simultaneously for generating a detection feedback signal, a resonant bridge circuit coupled to said vibrator and sensitive to a change of frequency, and a low resistance coupled to said vibrator for providing said detection feedback signal;
• a phase shift circuit having a limiter for adjusting the phase of both said detection feedback signal and an excitation signal to satisfy an oscillation condition;
• a phase locked loop (PLL) including a voltage controlled oscillator (VCO) and phase comparator for comparing the frequency and phase of the output of the phase shift circuit with an output frequency of the VCO for generating a difference signal, an amplifier, a low pass filter connected to apply said difference signal, having a frequency below a predetermined value, through said amplifier to said VCO, whereby the oscillation frequency of said VCO is controlled in the direction in which said difference signal is reduced;
• a second amplifier for amplifying the output of said PLL to a predetermined value and for outputting an excitation signal to said vibrator;
• an analog multiplier circuit connected to output a product of a current proportional signal and a voltage proportional signal from said resonant bridge circuit as an analog signal corresponding to a power consumption of said vibrator;
• a rectifier circuit for converting said analog signal to a direct current signal;
• and a direct current meter connected to indicate said direct current signal as the power consumption of said vibrator.