Method and apparatus for measuring fluid characteristics using surface generated volumetric interrogation signals

Apparatus for measuring a characteristic of a fluid comprising

• a solid plate-like material having a local surface and a remote surface, said remote surface being in contact with the fluid,
• a transducer means,
• means for coupling said transducer means to said local surface of said solid material,
• means for exciting said transducer means for generating along said local surface, Rayleigh-like surface waves having a wavelength .lambda..sub.R in said solid material,
• said local surface and said remote surface having a separation, in an interrogation direction, greater than one-half of a wavelength (.lambda..sub.R /2),
• said interrogation direction extending normal to said local surface, and
• said Rayleigh-like surface waves
• are non-dispersive, and
• have an intensity at said remote surface substantially less than the intensity at the local surface.

Apparatus for measuring a characteristic of a fluid comprising

• a solid plate-like material having a local surface and a remote surface, said remote surface being in contact with the fluid,
• a transducer means,
• means for coupling said transducer means to said local surface of said solid material,
• means for exciting said transducer means with a pulse signal sufficiently short to prevent intra-wall interference of said energy for generating along said local surface, Rayleigh-like surface waves having a wavelength .lambda..sub.R in said solid material,
• said local surface and said remote surface having a separation, in an interrogation direction, less than four wavelengths (4.lambda..sub.R),
• said interrogation direction extending normal to said local surface, and
• said Rayleigh-like surface waves
• are non-dispersive, and
• have an intensity at said remote surface substantially less than the intensity at the local surface.

A clamp-on ultrasonic flowmeter for measuring a characteristic of a fluid flowing in a conduit formed with a solid material wall having a local surface and a remote surface comprising

• a first and a second transducer means,
• means for coupling said first and second transducer means to said local surface of said conduit wall in an axially spaced relationship along said local surface of said conduit wall,
• means for selectively exciting said transducer means for generating, along said local surface of said conduit wall relative to said excited transducer means, Rayleigh-like surface waves having a wavelength .lambda..sub.R in said conduit wall,
• said conduit having a wall thickness less than four wavelengths (4.lambda..sub.R), said wall thickness being measured in a direction normal to propagation of said surface waves along said conduit.

A clamp-on ultrasonic flowmeter for measuring a characteristic of fluid flowing in a conduit having a local surface and a remote surface comprising

• a first and a second transducer means,
• means for coupling said first and second transducer means to said local surface of said conduit in an axially spaced relationship along said outside local surface of said conduit,
• means for selectively exciting said first and second transducer means for generating along said local surface Rayleigh-like surface waves having a wavelength .lambda..sub.R in said conduit,
• said conduit having a wall thickness greater than one-half of a Rayleight wavelength (.lambda..sub.R /2), and
• said Rayleigh-like surface waves
• being non-dispersive, and
• having an intensity at a conduit-fluid interface substantially less than the intensity at the local surface.

A method for measuring a characteristic of a fluid comprising

• contacting a remote surface of a plate-like solid material with said fluid,
• coupling a transducer to a local surface of a solid material for transmitting Rayleigh-like surface waves in said material,
• exciting said transducer for generating said Rayleigh-like surface waves having a wavelength in said material of .lambda..sub.R, and
• selecting a frequency of excitation for said transducer whereby a wall thickness between the local surface and a remote surface of said solid plate-like material is less than four Rayleigh wavelengths (4.lambda..sub.R).

A method for measuring a characteristic of a fluid comprising the steps of

• contacting a remote surface of a solid plate-like material with the fluid,
• coupling a transducer means to a local surface of said plate-like solid material,
• exciting said transducer means for generating along said local surface, Rayleigh-like surface waves having a wavelength .lambda..sub.R in said solid plate-like material, and
• said Rayleigh-like surface waves
• are non-dispersive, and
• have an intensity at said remote surface of said solid material, substantially less than the intensity at the local surface.

A method for measuring a characteristic of a fluid comprising the steps of

• contacting a remote surface of a solid plate-like material with the fluid,
• coupling a transducer means to a local surface of a said solid material,
• exciting said transducer means with a pulse signal sufficiently short to prevent intra-wall interference of said energy for generating along said local surface, a Rayleigh-like surface wave, having a wavelength .lambda..sub.R in said solid plate-like material,
• selecting a frequency of excitation for said transducer whereby said local surface and said remote surface have a separation, in an interrogation direction, greater than one half of a wavelength (.lambda..sub.R /2) and less than four wavelengths (4.lambda..sub.R),
• said interrogation direction extending normal to said local surface, and
• said Rayleigh-like surface wave
• is non-dispersive, and
• has an intensity at said remote surface of said solid material, substantially less than the intensity at the local surface.