Abstract: A method of calibrating an ultrasonic flow meter (10) first determines a static flow offset (52). Next, a dynamic flow offset (54) and a flow speed (56) are determined. An adjusted flow speed (58) is determined by subtracting the static flow offset and one half the dynamic flow offset from the flow speed to form an adjusted flow speed.

Abstract: A method of determining a characteristic of a fluid involves measuring a sonic transit time (102), along a non-perpendicular path, through the fluid. The sonic transit time is used to determine a speed of sound in the fluid (104). A measured flow rate (106) is determined from the sonic transit time. A friction factor (108) is calculated using the speed of sound and the measured flow rate. Next, a velocity profile (110) is determined using the friction factor. Finally, an adjusted flow rate is calculated (112) using the velocity profile.

Abstract: A method of calibrating an ultrasonic flow meter (10) first determines a static flow offset (52). Next, a dynamic flow offset (54) and a flow speed (56) are determined. An adjusted flow speed (58) is determined by subtracting the static flow offset and one half the dynamic flow offset from the flow speed to form an adjusted flow speed.

Abstract: An ultrasonic flow meter (10) has a pair of transducers (36, 38). A first (36) of the pair of transducers is coupled to a first divider (18) having a first predetermined divisor. A second (38) of the pair of transducers is coupled to a second divider (24) having a second predetermined divisor. The second predetermined divisor is not equal to the first predetermined divisor. An input (16) of the first divider (18) is coupled to a first oscillator (12). An input (22) of the second divider (24) is coupled to a second oscillator (14). A decoder circuit (50) is coupled to an output (15) of the first oscillator (12) and an output (20) of the second oscillator (14). The decoder circuit (50) determines a difference frequency.

Abstract: An apparatus (300) for detecting an ultrasonic signal (304) has a transducer (302) that produces an electrical signal (306) in response to the ultrasonic signal (304). A threshold comparator (308) receives the electrical signal (306) and produces a phase one signal (310) and a phase two signal (312). An arming circuit (314) receives the phase one signal (310) and the phase two signal (312) and producing an arming signal. A triggering circuit (316) receives the arming signal and the electrical signal (306) and produces a signal detected signal (318).

Abstract: An apparatus for controlling a voltage controlled oscillator (20) in an ultrasonic flow meter (18) includes a comparator (28) for comparing a received signal to an estimate signal, to form an early-late signal (32). The early-late signal (32) is received by a counter (36) to form a count signal (38). A digital to analog converter (42) receives the count signal (38) and converts it to a control voltage output (40) that is coupled to the voltage controlled oscillator (20).

Abstract: An apparatus for determining a flow count in an ultrasonic flow meter has an upstream oscillator (22) with an upstream signal (24) having a period proportional to an upstream transit time and a downstream oscillator (26) with a downstream signal (28) having a period proportional to a downstream transit time. The upstream signal (24) is coupled to a positive increment input (30) of a counter (32) and the downstream signal (28) is coupled to a negative increment input (36) the counter (32).

Abstract: A method of detecting and aligning a signal in an ultrasonic flow meter (18) generates an oscillator signal (50) and a transmit sequence (54) on a first predetermined trigger point (55) of the oscillator signal (50). The transmit sequence (54) is used to drive a transmit transducer (14, 16) to form a transmit waveform (60). The transmit waveform (60) is received by a receive transducer (14, 16) to form a received waveform. The received waveform is processed to form a received sequence (62). The received sequence (62) is then processed to sense an anomaly (80).

Abstract: A method of detecting a signal (50) in an ultrasonic flow meter sets a first threshold (52) and a second threshold (54) at a predetermined level above the first threshold (52). An ultrasonic signal (50) having a plurality of cycles is then received. Next it is determined when the ultrasonic signal (50) exceeds the first threshold (52). This time is marked a first threshold time. Then it is determined when the ultrasonic signal exceeds the second threshold (54). This time is marked a second threshold time. A time difference between the first threshold time and the second threshold time (56) is determined. When the time difference (56) exceeds a delta time, increasing the first threshold (52) a delta level.

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.

Abstract: A meter for measuring the velocity of a fluid by ascertaining propagation periods of acoustic wave packets transmitted therein, the meter including a pair of transducers for disposition in the fluid, a transmitter for transmitting a packet between the transducers in an upstream or downstream direction designated by an up/down signal at each time designated by a transmit signal and a receiver for developing a received signal marking the time of receipt by a transducer of each packet, the times being marked so as to avoid amplitude and half-cycle ambiguity errors.

Abstract: In an ultrasonic flowmeter ultrasonic signals are transmitted alternately upstream and downstream of a fluent media whose flow velocity is to be ascertained. The repetition rate at which signals are transmitted is controlled by a voltage controlled oscillator. To increase the sensitivity of the meter, the frequency of the voltage controlled oscillator, which is related to sound speed through the fluent media, is increased.

Abstract: A high temperature ultrasonic transducer is described in which a piezoelectric crystal is held in contact with an acoustical diaphragm by a spring which also electrically couples the back face of the crystal to an electrical signal source. An oil film between the diaphragm and crystal provides an acoustical coupling. Air is used to insulate the spring electrical connection from the wall of the transducer.

Abstract: Volumetric fluid flow in a cylindrical conduit is determined by measuring the average flow velocity of the fluid flowing through a chordal measuring path lying at a radial distance of 0.54R where R is the radius of the conduit. This average flow velocity is multiplied by constants related to the location of the chordal path and to the chordal path length. The average flow velocity measurement is made by the use of an ultrasonic flow meter having upstream and downstream transducers which define the chordal measuring path. Multiple measuring paths are preferred.

Abstract: Fluid flow in small bore conduits is measured and controlled utilizing a Doppler flowmeter to measure flow rate. The fluid is then passed through a static chamber in which sound speed in the fluid is measured by a velocimeter. The outputs of the flowmeter and the velocimeter are multiplied to correct the measured flow rate for errors due to its sound speed dependency. The corrected flow rate may be then used to control a pump to provide the desired flow rate.