Measuring and testing – Volume or rate of flow – By measuring vibrations or acoustic energy
Patent
1980-07-28
1982-06-08
Kreitman, Stephen A.
Measuring and testing
Volume or rate of flow
By measuring vibrations or acoustic energy
128663, G01F 166
Patent
active
043333532
ABSTRACT:
A flowmeter clamped onto the outside of a conduit uses doppler techniques for measuring the flow velocity of a fluid within the conduit. Separated transmitter and receiver transducers are connected to different locations on the conduit. An oscillator connected to the transmit crystal causes the crystal to produce a continuous high frequency output wave which is injected through the pipe wall and into the fluid. The frequency of the transmit oscillator is cyclically swept through a given frequency range. The receiver transducer receives reflected sonic signals from particles moving with the fluid whose velocity is to be measured. The receiver crystal also receives, through the pipe wall, the transmitted wave form. The transmitted signal and received signal are added together to produce an amplitude-modulated envelope having a beat frequency related to the flow velocity of particles producing the reflected signal received by the receiving crystal. By using frequency sweep or dither, the effect of standing waves at the receiving crystal is eliminated since, during the sweep cycle, at least one transmitter signal amplitude will be present to produce an optimum beat frequency output when added to the reflected signal. The measured amplitude-modulated wave is applied to an amplitude demodulator which, in turn, is connected to a flow indicator. Means are provided to control the amplitude of the transmit signal which is added to the receive signal to prevent the receive signal from overwhelming the pipe conducted transmit signal in the summation process producing the beat frequency.
REFERENCES:
patent: 4147059 (1979-04-01), Fathauer
K. McCarty et al., "Frequency Modulated Ultrasonic Doppler Flowmeter," Medical and Biological Engineering, vol. 13, No. 1, pp. 59-64, Jan. 1975.
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