Abstract: A transit-time flowmeter transmits trains of ultrasonic pulses alternately upstream and downstream through a conduit having liquid flowing therein. Flow speed (fv) is a function of the total liquid travel time (t.sub.L) and the difference (.DELTA.t) between the upstream and downstream travel times. The timer t.sub.L is determined by transmitting a short setup pulse train, for example, 1-3 pulses, from one of the transducers. The time the short pulse train is received by the other transducer is taken to define an overall travel time t.sub.N. The known pulse travel time within the transducers and pipe walls is subtracted from the time t.sub.N, the result being the liquid travel time t.sub.L. To measure .DELTA.t, a longer measurement pulse train (Tx), for example 8-100 pulses, is transmitted alternately upstream and downstream. The phase difference is measured between the received (digitized) pulse train R.sub.D and a reference pulse train f.sub.

Abstract: The transducers in a transit time clamp-on flowmeter are positioned relative to one another by abutting against pin stops located in selected openings of one or more rows of openings extending longitudinally along the pipe axis. A block of sound-absorbing material is fixed to the conduit surface between the spaced transducers and tends to absorb sound energy flowing in the pipe wall between the transducers and substantially improves the signal-to-noise ratio of the system.

Abstract: A couplant material for establishing a sonic path of good acoustical impedance between an ultrasonic transducer and a sonic medium. The material is capable of being easily shaped at room temperature and withstanding vibration and thermal cycling from room temperature to over 500.degree. F. while substantially maintaining its acoustical properties and providing a minimum of irritating fumes and outgasses. A preferred couplant material is a polytetrafluoroethylene grease or perfluoropolyalkylether grease, which have been used previously as lubricants.

Abstract: The transducer housings for clamp-on transducers of a flowmeter system are cast of an aluminum zinc alloy which is sonically conductive after casting. The transducer housings have a shear mode converting surface which has a longitudinal curvature and a cross-curvature. The cross-curvature of the shear mode conversion surface defines a solid lens which tends to focus internally reflected shear mode converted energy along the line of intersection of the flat output surface of the transducer housing with a circular metal conduit. The longitudinal curvature of the shear mode converting surface adjusts the phase velocity over the transducer output surface so as to focus the beam and reduce beam spreading along the length of the pipe and generally to correct aperture dispersion. A relatively low Q transducer crystal assembly is coupled to the aluminum-zinc alloy housing.

Abstract: The transducer housings for clamp-on transducers of a flowmeter system are cast of an aluminum zinc alloy which is sonically conductive after casting. The transducer housings have a shear mode converting surface which has a longitudinal curvature and a cross-curvature. The cross-curvature of the shear mode conversion surface defines a solid lens which tends to focus internally reflected shear mode converted energy along the line of intersection of the flat output surface of the transducer housing with a circular metal conduit. The longitudinal curvature of the shear mode converting surface adjusts the phase velocity over the transducer output surface so as to focus the beam and reduce beam spreading along the length of the pipe and generally to correct aperture dispersion. A relatively low Q transducer crystal assembly is coupled to the aluminum-zinc alloy housing.

Abstract: A pair of transducers each having metal housings are clamped at spaced axial locations along a conduit and transmit ultrasonic signals to one another through the fluid within the conduit. The difference in upstream and downstream transit times for the ultrasonic energy is used to determine the flow velocity and other characteristics of the fluid within the conduit. Each of the transducer housings has the shape of a trapezohedron, one surface of which converts longitudinal mode sonic energy from a transducer crystal into reflected shear mode sonic energy which is applied at an angle to the pipe surface. The phase velocity of the shear mode sonic energy of the transducer housing matches the shear mode sonic energy in the conduit wall so that there is extremely close coupling between the housing and the conduit and energy is transmitted through the conduit interior over a long axial length of the conduit.

Abstract: A transducer crystal is coupled to a coupling plastic material made of a compression molded polyimid amide. Two cooperating transducer housings are formed of two wedges of material cut from the same rectangular billet. The wedge angle is calculated after measuring the sonic velocity of the billet. A novel buffer is applied to the rear surface of the transducer crystal and consists of an epoxy body having tungsten powder and small particles of an elastomer distributed therein. The transducer body is mounted on a support track which has a similar configuration for numerous different mounting arrangements. The transducer housings are axially spaced from one another along the axis of the pipe and are set to a given spacing by locating a mounting clip on an index plate on the track. Transducers for a portable type application have tracks connected to one another along one of their sides by a flexible but tough sheet of material which fixes the spacing of the tracks for a given pipe diameter.

Abstract: A transducer crystal is coupled to a coupling plastic material made of a compression molded polyimid amide. Two cooperating transducer housings are formed of two wedges of material cut from the same rectangular billet. The wedge angle is calculated after measuring the sonic velocity of the billet. A novel buffer is applied to the rear surface of the transducer crystal and consists of an epoxy body having tungsten powder and small particles of an elastomer distributed therein. The transducer body is mounted on a support track which has a similar configuration for numerous different mounting arrangements. The transducer housings are axially spaced from one another along the axis of the pipe and are set to a given spacing by locating a mounting clip on an index plate on the track. Transducers for a portable type application have tracks connected to one another along one of their sides by a flexible but tough sheet of material which fixes the spacing of the tracks for a given pipe diameter.

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.

Abstract: A sonic flow meter for measuring the rate of flow of a fluid within an enclosed axially elongated hollow conduit is disclosed. First and second transducers are secured to the exterior surface of the conduit. The transducers are spaced from each other along the axis of the conduit such that the first transducer is located downstream from the second transducer with respect to the direction of flow of the fluid. Each of the transducers are adapted to transmit to each other, and receive from each other, sinusoidal sonic signals which pass through the fluid in the conduit. Sonic signal transmission means are provided for causing a plurality of sonic signals to be transmitted in an upstream direction from the first to the second transducer means and for causing an equal plurality of sonic signals to be transmitted in a downstream direction from the second to the first transducer means.

Abstract: A method and apparatus for determining a fluid condition adjacent an inner wall boundary of a fluid container is disclosed. A sonic pulse is applied to an outer wall boundary of the container wall and is reflected between an inner and the outer wall boundaries. The magnitude of the sonic pulse decreases each time it is reflected off of the inner wall boundary by an amount which varies as a function of the fluid condition adjacent the inner wall boundary. An electrical reflection pulse whose magnitude is representative of the instantaneous magnitude of the sonic pulse is generated each time the sonic pulse is reflected off of the outer wall boundary of the container. The electrical reflection pulses are integrated during an integration period so as to generate an integration output signal whose value varies as a function of the fluid condition within the container. The integration output signal is compared to a predetermined value to determine the fluid condition.

Abstract: The presence or absence of liquid at a particular location of a tank or pipe is sensed through the wall of the container by a single ultrasonic transducer which may be secured to the outer surface of the container by hand pressure, by clamping, or by cementing. Detection is obtained through the damping effect of either liquid or air within the container on multiple interface reflections of a longitudinal sonic beam in the container wall. The first return signal amplitude adjusts the gain of the monitoring circuit and allows the measurement of the percentage decay of the return signal and the comparison of the decay to the known decay rate if the container was either empty or full at the point of measurement. Output circuits are provided to give a full or empty output signal, or to provide output control signals in response to the fluid level measurement. A fault alarm signal is also produced to indicate that the transducer is not properly coupled to the container or that the circuit is working improperly.

Abstract: An open channel flow transducer is provided for measurement of the flow of liquid in a sewer pipe or the like which is not always completely filled. A flow tube which may be of plastic has an upwardly extending discharge region connected to a sewer pipe, as by connection to the outlet opening of a sewer pipe which extends into a manhole or other access area. The flow tube therefore becomes filled with liquid before the liquid can be vertically discharged. A flow measuring transducer system is then connected in the flow tube to make a measurement of one or both the flow rate in the tube or the material flowing in the tube by ultrasonic measurement techniques.

Abstract: Transducers are positioned on opposite sides of a fluid conduit and are longitudinally displaced from one another along the axis of the conduit. Each transducer contains a transmitting and receiving transducer element which produces output energy in a direction represented by a ray forming an angle to the axis of the flow conductor, such that the sine of the angle is equal to the ratio of the velocity of sound in the transducer body supporting the transducer crystal to the shear mode sound velocity in the conduit walls of the conduit conducting the fluid. The longitudinal spacing between the centers of the transducers on opposite sides of the conduit is such that it intercepts a sonic beam passing through the liquid. The sine of the angle of that beam passing through the fluid within the conduit and between the transducers makes with a line normal to the axis of the pipe, equals the ratio of the velocity of sound in the liquid to the pipe shear mode velocity of sound in the conduit.