초록 ▼

In a flowmeter system having a transducer assembly defining a path for confining the flow of fluid medium there through and with first and second acoustic transducer elements disposed along said flow path for generating and receiving acoustic compression waves in the fluid medium, a phase-locked loo

In a flowmeter system having a transducer assembly defining a path for confining the flow of fluid medium there through and with first and second acoustic transducer elements disposed along said flow path for generating and receiving acoustic compression waves in the fluid medium, a phase-locked loop transmitter/receiver system including a voltage-controlled oscillator for adjusting the frequency of the acoustic compression waves to maintain the compression wavelength constant, together with circuitry for measuring the phase difference of the received acoustic compression waves relative to the applied electrical signal and circuitry for producing a signal representative of both the velocity of sound in the fluid medium and the direction and magnitude of the flow, the improvement in the circuitry which enables operation over a wider range of fluid density by causing the operating phase of the system phase-locked loop to vary in a continuous manner according to a previously determined relationship of phase-versus-resonant frequency, and the loop acquisition frequency to vary in a continuous manner according to a previously determined relationship of amplitude-versus-resonant frequency, of the transducer due to the density of the fluids being measured. Disclosed are three embodiments of the improved circuitry which vary the phase-locked loop operating phase and acquisition frequency, either nonlinearly or linearly, depending on the density range of the gases to be monitored.

대표청구항 ▼

A phase-locked loop system for measuring fluid flow by detecting phase differences between a transmitted and received signal within a confined path having a voltage controlled oscillator, applying signals at a given frequency from said voltage controlled oscillator to said fluid in said flow path, a

A phase-locked loop system for measuring fluid flow by detecting phase differences between a transmitted and received signal within a confined path having a voltage controlled oscillator, applying signals at a given frequency from said voltage controlled oscillator to said fluid in said flow path, a phase detector for detecting the phase difference between the received signal and the transmitted signal, means for generating an error voltage corresponding to said detected phase difference between the transmitted and received signal and applying said error voltage to said voltage controlled oscillator so that said transmitted signal will be maintained in operating phase with the received signal, and means for varying the operating phase between said transmitted signal and said received signal in a continuous manner according to a predetermined relationship of acoustic resonance of the confined path with fluids of different densities therein, wherein said means for varying is coupled to control the phase of said signals from said voltage controlled oscillator in cooperation with said means for generating an error voltage.