Abstract: A circuit simulating the electrical signal response of a flowing liquid whose velocity is to be measured by an upstream-downstream flowmeter. The circuit takes the electrical flowmeter transmit signal from an upstream-downstream flowmeter and actuates a gated oscillator which feeds pulses to a counter, establishing an electrical signal which has a duration of almost the mean transit time of an acoustic signal traveling between transducers and the flowmeter. This signal is incremented by further pulse counts and these further pulses are indicative of the exact mean transit time, plus pulses arriving on either side of the exact mean transit time, indicative of the upstream and downstream transit times. The upstream and downstream pulses are fed to a second oscillator for wave shaping. The second oscillator and associated circuitry simulates electrical signals produced by a transducer receiver in the flowmeter.

Abstract: A circuit simulating the electrical signal response of a flowing liquid whose velocity is to be measured by a Doppler flowmeter. The circuit takes the electrical flowmeter transmit signal from a Doppler flowmeter and modifies its frequency to derive a simulated Doppler shifted signal. The latter signal is used to modulate the transmit signal in a double side band, balanced modulator which suppresses the frequency of the transmit signal and produces upper and lower side band frequencies mimicking a Doppler shifted return signal. The latter signal is fed to the signal receiving transducer of a Doppler flowmeter for test purposes.

Abstract: An ultrasonic flowmeter of the upstream-downstream type having piezoelectric crystals operated in the radial mode, as well as the compression mode, or primarily the radial mode. If both modes are used, one of the two may be selected in order to optimize the received signal. Selection would depend upon the molecular weight and temperature of the viscous fluid in the flowmeter. The selected frequency would be below the relaxation frequency of the flowing material. Radial mode oscillations are achieved by mass loading members adhered to either side of the crystal, thereby creating acoustic impedances which dampen the compressional mode, but enhance the radial mode of vibration. The mass loading member rearward of the crystal is significantly larger than the forward member so that most of the energy to be transmitted is directed in a forward direction. The forward end of the crystal is mounted in a tubular housing which is inserted into a pipe opening into a larger pipe where fluid flow occurs.

Abstract: A Doppler flowmeter which utilizes a single crystal immersed in the flow stream directing energy in a direction parallel with the flow direction. The crystal is fed by an oscillator at a single frequency corresponding to an ultrasonic vibrational mode for the crystal. The crystal also detects reflected acoustic wave energy with the input and output signals being electrically combined in the crystal. An electrical discriminator circuit is able to separate a multi-spectral Doppler signal from the crystal by phase cancellation of the transmitted signal. The recovered signal is fed to a tunable state variable filter which establishes a ninety degree phase shift with the incoming multi-spectral signal. This phase shifted signal is combined with the incoming multi-spectral signal in a phase lock loop with an output of the loop used to clock the state variable filter. Another output is a synthesized Doppler frequency representative of the mean Doppler frequency.

Abstract: A calibration circuit for an ultrasonic flowmeter of the type described in U.S. Pat. No. 3,981,191 wherein a frequency counted variable delay is used to simulate flow. A stable gated oscillator is used to feed a counter whose accuracy is checked against a frequency standard. A BCD switch is used to load the counter with a count representing a desired variable delay. When the count is reached the oscillator is stopped and a variable delay signal is put out by the counter, to be combined with a fixed delay signal for simulation of flow in the upstream or downstream channel of the flowmeter.

Abstract: An apparatus for the ultrasonic measurement of cryogenic or high viscosity fluid flow provides for precooling and symmetrical flow in the measuring run of one of two coaxial inner and outer cylinders. A baffle in one of the cylinders directs fluid flow so as to encircle the measuring path cylinder thereby cooling it and reducing heat loss and flashing against the walls. Symmetrical entry and exit of the fluid flow in and out of the measuring cylinder eliminates the effects of velocity gradients on the ultrasonic measuring signals. Inlet and outlet ports are located perpendicular to the coaxial cylinders allowing a longer measuring run without requiring a similar interruption to the pipe system being monitored.