BACKGROUND OF THE INVENTION
The subject matter disclosed herein relates to an ultrasonic flow measurement
system.
Flow meters, including ultrasonic flow sensors, are used to detennine the
characteristics (e.g., flow rate, pressure, temperature, etc.) ofliquids, gases, etc. flowing
in pipes of different sizes and shapes. Knowledge ofthese characteristics ofthe fluid can
enable other physical properties or qualities ofthe fluid to be determined. For example,
in some fluid custody-transfer applications, the flow rate ofthe fluid can be used to
determine the volume of a fluid (e.g., oil or gas) being transferred from a seller to a buyer
through a pipe over a period oftime to determine the costs for the transaction! The
volume is equal to the measured fluid flow rate multiplied by the cross sectional area of
the pipe multiplied by the period of time over which the fluid flow is measured.
In one type ofultrasonic flow sensor employing transit time flow metering,
one or more pairs ofultrasonic flow sensors can be installed along a portion of a pipe,
referred to as a flow cell. Each pair ofultrasonic flow sensors contain an ultrasonic
transducer and an ultrasonic buffer that are located upstream and downstream from each
other, forming an ultrasonic path between these ultrasonic flow sensors at particular
chordal locations across the pipe.
Each transducer, when energized, transmits an ultrasonic signal (e.g., a sound
wave) along an ultrasonic path through the flowing fluid that is received by and detected
by the other transducer. The path velocity ofthe fluid averaged along the ultrasonic path
at a particular chordal location can be determined as a function of the differential between
(1) the transit time of an ultrasonic signal traveling along the ultrasonic path from the
downstream transducer upstream to the upstream transducer against the fluid flow
direction, and (2) the transit time of an ultrasonic signal traveling along the ultrasonic
path from the upstream transducer downstream to the downstream transducer with the
2
fluid flow direction. Ultrasonic flow meters use signal processing techniques to identify
the ultrasonic signals received by the transducers and the time that those ultrasonic
signals were received in order to determine the transit times used to determine the flow
rate of the fluid.
In some ultrasonic flow measurement systems (e.g., ultrasonic signals of a few
megahertz or less where the wavelength ofthe ultrasonic signal is not significantly less
than the diameter ofthe ultrasonic buffers), the spreading ofthe ultrasonic signal beam as
it propagates within the ultrasonic buffer can result in distortion in the form ofmultiple
ring-down signals and peaks in the received ultrasonic signal. This distortion is a result of
angular portions ofthe ultrasonic signal reflecting off ofthe walls ofthe ultrasonic
buffer. When these ring-down signals and peaks resulting from the distortion have
amplitudes that are comparable or greater than the amplitudes of the main (non-angular)
portion of the ultrasonic signal, the signal processing ofthe ultrasonic flow meter may
not be able to accurately identify the main portion ofthe ultrasonic signal from which the
transit time is determined.
The discussion above is merely provided for general background information
and is not intended to be used as an aid in determining the scope of the claimed subject
matter.
BRIEF DESCRIPTION OF THE INVENTION
An ultrasonic flow measurement system having a first ultrasonic sensor with a
first ultrasonic buffer and a second ultrasonic sensor with a second ultrasonic buffer is
disclosed. The first and second ultrasonic buffers have different cross sections in order to
reduce distortion of the ultrasonic signals. An advantage that may be realized by the
practice of some of the disclosed embodiments ofthe ultrasonic flow measurement
system is improving the accuracy ofthe measured transit times.
In one embodiment, an ultrasonic flow measurement system is disclosed.
The system comprises a first ultrasonic sensor comprising a first ultrasonic transducer
3
and a fIrst ultrasonic buffer, and a second ultrasonic sensor comprising a second
ultrasonic transducer and a second ultrasonic buffer, the second ultrasonic sensor is
aligned with the fIrst ultrasonic sensor along an axis, wherein the fIrst ultrasonic buffer
has a fIrst cross section that is perpendicular to the axis and the second ultrasonic buffer
has a second cross section that is perpendicular to the axis, and wherein the fIrst cross
section ofthe fIrst ultrasonic buffer is different from the second cross section ofthe
second ultrasonic buffer.
In another embodiment, the ultrasonic flow measurement system comprises a
fIrst ultrasonic sensor comprising a fIrst ultrasonic transducer and a fIrst ultrasonic buffer,
and a second ultrasonic sensor comprising a second ultrasonic transducer and a second
ultrasonic buffer, the second ultrasonic sensor is aligned with the frrst ultrasonic sensor
along an axis, wherein the frrst ultrasonic buffer has a frrst cross section that is
perpendicular to the axis and the second ultrasonic buffer has a second cross section that
is perpendicular to the axis, and wherein the frrst cross section ofthe fIrst ultrasonic
buffer has a fIrst shape and the second cross section ofthe second ultrasonic buffer has a
second shape, and wherein the fIrst shape is different from the second shape.
In yet another embodiment, the ultrasonic flow measurement system
comprises a fIrst ultrasonic sensor comprising a frrst ultrasonic transducer and a fIrst
ultrasonic buffer, and a second ultrasonic sensor comprising a second ultrasonic
transducer and a second ultrasonic buffer, the second ultrasonic sensor is aligned with the
fIrst ultrasonic sensor along an axis, wherein the frrst ultrasonic buffer has a frrst cross
section that is perpendicular to the axis and the second ultrasonic buffer has a second
cross section that is perpendicular to the axis, and wherein the frrst cross section ofthe
fIrst ultrasonic buffer has a fIrst diameter and the second cross section of the second
ultrasonic buffer has a second diameter, and wherein the fIrst diameter is different from
the second diameter.
This brief description ofthe invention is intended only to provide a brief
overview of subject matter disclosed herein according to one or more illustrative
4
embodiments, and does not serve as a guide to interpreting the claims or to defme or limit
the scope of the invention, which is defmed only by the appended claims. This brief
description is provided to introduce an illustrative selection of concepts in a simplified
form that are further described below in the detailed description. This brief description is
not intended to identify key features or essential features of the claimed subject matter,
nor is it intended to be used as an aid in determining the scope of the claimed subject
matter. The claimed subject matter is not limited to implementations that solve any or all
disadvantages noted in the background.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the features of the invention can be understood, a
detailed description ofthe invention may be had by reference to certain embodiments,
some ofwhich are illustrated in the accompanying drawings. It is to be noted, however,
that the drawings illustrate only certain embodiments ofthis invention and are therefore
not to be considered limiting of its scope, for the scope of the invention encompasses
other equally effective embodiments. The drawings are not necessarily to scale,
emphasis generally being placed upon illustrating the features of certain embodiments of
the invention. In the drawings, like numerals are used to indicate like parts throughout
the various views. Thus, for further understanding ofthe invention, reference can be
made to the following detailed description, read in connection with the drawings in
which:
FIG. 1 is a diagram of an exemplary ultrasonic flow measurement system;
FIG. 2 illustrates a cross sectional view ofthe exemplary first ultrasonic
buffer of FIG. 1;
FIG. 3 illustrates a cross sectional view of the exemplary second ultrasonic
buffer of FIG. 1;
5
FIG. 4 illustrates a plurality ofultrasonic signal paths traveling from the ftrst
ultrasonic buffer to the second ultrasonic buffer ofFIGS 1-3;
FIG. 5 illustrates a plurality ofreceived ultrasonic signal waveforms
corresponding to the ultrasonic signal as it is received by the second ultrasonic transducer
via the ultrasonic signal paths of FIG. 4;
FIG. 6 illustrates a cross sectional view of an exemplary third ultrasonic
buffer;
FIG. 7 illustrates a plurality of signal paths traveling from the ftrst ultrasonic
buffer to the third ultrasonic buffer;
FIG. 8 illustrates a plurality of signal paths traveling from the ftrst ultrasonic
buffer to the third ultrasonic buffer;
FIG. 9 illustrates a plurality ofreceived ultrasonic signal waveforms
corresponding to the ultrasonic signal as it is received by the second ultrasonic transducer
via the ultrasonic signal paths of FIGS. 7-8;
FIG. 10 illustrates a cross sectional view of an exemplary fourth ultrasonic
buffer;
FIG. 11 illustrates a plurality ofultrasonic signal paths traveling from the ftrst
ultrasonic buffer to the fourth ultrasonic buffer;
FIG. 12 illustrates a plurality ofreceived ultrasonic signal waveforms
corresponding to the ultrasonic signal as it is received by the second ultrasonic transducer
via the ultrasonic signal paths of FIG. 11;
FIG. 13 illustrates a cross sectional view of an exemplary ftfth ultrasonic
buffer;
6
FIG. 14 illustrates a plurality ofultrasonic signal paths traveling from the first
ultrasonic buffer to the fifth ultrasonic buffer; and
FIG. 15 illustrates a plurality ofreceived ultrasonic signal waveforms
corresponding to the ultrasonic signal as it is received by the second ultrasonic transducer
via each of the ultrasonic signal paths of FIG. 14.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram of an exemplary ultrasonic flow measurement system 100.
As shown, this system 100 includes a first ultrasonic flow sensor 170 and a second
ultrasonic flow sensor 180. The first ultrasonic flow sensor 170 includes a first ultrasonic
buffer 172 and a first transducer 174. The second ultrasonic flow sensor 180 includes a
second ultrasonic buffer 182 and a second transducer 184. Each ultrasonic flow sensor
170,180 is designed to transmit and receive ultrasonic signals. The pipe 190 is designed
to transport a fluid 192 that is in a liquid state, a gas state, or a combination of liquid and
gas. The first and second ultrasonic flow sensors 170, 180 are each installed into the pipe
190 and each have ultrasonic buffers 172, 182 aligned along a common axis 150. The
common axis 150 can be at an angle which is perpendicular to the axis of the pipe 190
where no flow is detected or at an angle other than ninety degrees with respect to the axis
of the pipe 190 to detect flow.
FIG. 2 illustrates a cross sectional view of the exemplary first ultrasonic
buffer 172, while FIG. 3 illustrates a cross sectional view of the exemplary second
ultrasonic buffer 182 of FIG. 1. As shown in these figures, the first ultrasonic buffer 172
has a cross section (i.e., circular in shape) with a first diameter 179, while the second
ultrasonic buffer 182 has a cross section (i.e., circular in shape) with a second diameter
189.. Both cross sections and other cross sections described within this document are
defined along a plane that is perpendicular to the axis 150 (FIG. 1). Comparing FIGS. 2
and 3 shows that the cross section of the first ultrasonic buffer 172 is the same shape and
size as the cross section of the second ultrasonic buffer 182. In one embodiment, the
7
diameters 179, 189 are 0.5 inches (12.7 millimeters). As will be explained, since the
cross section of the first ultrasonic buffer 172 is the same as the cross section of the
second ultrasonic buffer 182, this symmetry will produce significant distortions (ringdown
signals, peaks) in the received ultrasonic signal.
FIG. 4 illustrates a plurality of ultrasonic signal paths 110, 120, 130 traveling
from the first ultrasonic buffer 172 to the second ultrasonic buffer 182 of FIGS. 1-3. The
ultrasonic signal is transmitted from the first transducer 174 via the first ultrasonic buffer
172 to the second ultrasonic flow sensor 180 via the second ultrasonic buffer 182. A
portion of the ultrasonic signal is transmitted along a first (main) ultrasonic signal path
110, which is co-axial with axis 150 of FIG. 1. This first ultrasonic signal path 110 is a
straight and direct path from the first ultrasonic buffer 172 to the second ultrasonic buffer
182. As a result of beam spread of the ultrasonic signal, angular components of the
ultrasonic signal travel along many other ultrasonic signal paths in addition to the first
ultrasonic signal path 110. For example, portions of the ultrasonic signal also travel
along a second ultrasonic signal path 120 and a third ultrasonic signal path 130.
The second ultrasonic signal path 120 is initially directed at a 10 degree angle
122 from a center location 121 along the back wall 175 ofthe first ultrasonic buffer 172.
This second ultrasonic signal path 120 changes direction at the face 176 ofthe first
ultrasonic buffer 172, where it refracts into the fluid 192. The second ultrasonic signal
path 120 changes direction at the face 186 of the second ultrasonic buffer 182 where it
refracts from the fluid 192 into the second ultrasonic buffer 182. The second ultrasonic
signal path 120 changes direction again when it reflects off the lower wall 187 ofthe
second ultrasonic buffer 182. The second ultrasonic signal path 120 changes direction
again when it reflects off the upper wall 188 ofthe second ultrasonic buffer 182. The
second ultrasonic signal path 120 exits the second ultrasonic buffer 182 along the back
wall 185 ofthe second ultrasonic buffer 182 and is received by the second ultrasonic
transducer 184. As shown, the second ultrasonic sign~l path 120 is longer than the first
ultrasonic signal path 110.
8
The third ultrasonic signal path 130 is initially directed at a 10 degree angle
132 from a non-center location 131 along the back wall 175 ofthe first ultrasonic buffer
172. The second ultrasonic signal path 130 changes direction when it reflects off the
lower wall 177 ofthe first ultrasonic buffer 172. The third ultrasonic signal path 130
changes direction and reflects off an upper wall 178 ofthe first ultrasonic buffer 172.
Next, the third ultrasonic signal path 130 changes direction at the face 176 of the first
ultrasonic buffer 172, where it refracts into the fluid 192. The third ultrasonic signal
path 130 changes direction at the face 186 of the second ultrasonic buffer 182 where it
refracts from the fluid 192 into the second ultrasonic buffer 182. The third ultrasonic
signal path 130 exits the second ultrasonic buffer 182 along the back wall 185 ofthe
second ultrasonic buffer 182 and is received by the second ultrasonic transducer 184. As
shown, the third ultrasonic signal path 130 is longer than the first ultrasonic signal path
110, but is the same length as the second ultrasonic signal path 120.
FIG. 5 illustrates a plurality ofreceived ultrasonic signal waveforms 210, 220,
230 corresponding to the ultrasonic signal as it is received by the second ultrasonic
transducer 184 via each ofthe ultrasonic signal paths 110, 120, 130 of FIG. 4. It should
be noted that the graph of FIG. 5 (and all other graphs herein) show the ultrasonic signal
waveforms on the same voltage (y) axis to illustrate the relative amplitudes of each
ultrasonic waveform. Each ultrasonic signal waveform 210,220,230 is a representative
portion of the ultrasonic signal. As shown, the first ultrasonic signal waveform 210 is
received via the first ultrasonic signal path 110, the second ultrasonic signal waveform
220 is received via the second ultrasonic signal path 120, and the third ultrasonic signal
waveform 230 is received via the third ultrasonic signal path 130. The fourth (combined)
ultrasonic signal waveform 240 is the ultrasonic signal waveform received from the
combination of the ultrasonic signal paths 110, 120, 130.
Each ofthe ultrasonic signal waveforms 210, 220, 230 includes a leading edge
212,222,232, respectively, that arrives at a particular time. In one exemplary ultrasonic
flow measurement system (l MHz ultrasonic signal, the first and second ultrasonic
9
buffers 172, 182 are made from 88316 stainless steel, each having a 0.50 in (12.70 mm)
diameter by 0.75 in. (19.05 mm) length, with 1.0 in. (25.4 mm) water separation between
the ultrasonic buffers 172, 182), the leading edge 212 ofthe first ultrasonic signal
waveform 210 is received by the second ultrasonic transducer 184 via the first ultrasonic
signal path 110 at a time of23.53 microseconds. The leading edge 222 ofthe second
ultrasonic signal waveform 220 is received via the second ultrasonic signal path 120 at a
time of 27.11 microseconds. The leading edge 232 of the third ultrasonic signal
waveform 230 is received via the third ultrasonic signal path 130 at a time of27.11
microseconds, the same time as the leading edge 222 ofthe second ultrasonic signal
waveform 220.
The first portion 214 of the combined ultrasonic signal waveform 240 is the
portion of the received ultrasonic signal contributed by the first ultrasonic signal
waveform 210 received via the first ultrasonic signal path 110 from which the transit time
should be determined. But since the second and third ultrasonic signal waveforms 220,
230 arrive at the same time (27.11 microseconds), the constructive combination of these
ultrasonic signal waveforms 220, 230 forms a second portion 244 of the combined
ultrasonic signal waveform 240 that has a greater amplitude than the first portion 214 of
the combined ultrasonic signal waveform 240. This second portion 244 of the combined
waveform can produce unwanted ring-down signals and peaks in the combined ultrasonic
signal waveform 240 that can result in the signal processing electronics of the ultrasonic
flow measurement system being unable to accurately identify the first portion 214 of the
combined ultrasonic waveform 240 from which the transit time ofthe ultrasonic signal is
determined.
To address this problem, embodiments ofthe invention reduce the
constructive combination ofultrasonic signal waveforms that are received from the
angular ultrasonic signal paths so that the first (main) ultrasonic signal waveform of the
first (main) ultrasonic signal path is more easily identifiable by the signal processing
electronics. This reduction is accomplished using ultrasonic buffers having different
10
cross sections to reduce the symmetry ofthe ultrasonic signal paths in the ultrasonic flow
measurement system, creating different ultrasonic signal path lengths for the angular
components of the ultrasonic signal.
FIG. 6 illustrates a cross sectional view of an exemplary third ultrasonic
buffer 382. Comparing FIG. 2 with FIG. 6 shows that the cross section of the first
ultrasonic buffer 172 is different than the cross section of the third ultrasonic buffer 382.
As shown, the third ultrasonic buffer 382 has a cross section having a first section 383
that has a circular shape and a second section 384 forming a straight line edge 398. This
cross section is referred to herein as having a letter "D" shape. The "D" shape shown in
FIG. 6 is different than the circular "0" cross section shape of first ultrasonic buffer 172
shown in FIG. 2. This "D" shape cross section has a first dimension 397 and a second
dimension 399. In one embodiment, the first dimension 397 is 0.427 inches (10.85
millimeters) and the second dimension 399 is 0.5 inches (12.7 millimeters).
FIG. 7 illustrates a plurality of ultrasonic signal paths 310, 320 traveling from
the first ultrasonic buffer 172 (FIG. 2) to the third ultrasonic buffer 382 of FIG. 6, as seen
from a first perspective. The third ultrasonic buffer 382 is shown where the first
dimension 397 is the distance between the lower wall 387 and the straight line edge 398,
which constitutes an upper wall of the third ultrasonic buffer 382. The ultrasonic signal
is transmitted from the first transducer 174 via the first ultrasonic buffer 172 to the
second transducer 184 via the third ultrasonic buffer 382. A portion of the ultrasonic
signal is transmitted along a first (main) ultrasonic signal path 310, which is co-axial with
axis 150 of FIG. 1. This first ultrasonic signal path 310 is a straight and direct path from
the first ultrasonic buffer 172 to the third ultrasonic buffer 382. As a result of beam
spread of the ultrasonic signal, angular components of the ultrasonic signal travel along
many other ultrasonic signal paths in addition to the first ultrasonic signal path 310. For
example, portions of the ultrasonic signal also travel along a second ultrasonic signal path
320 (FIG. 7) and a third ultrasonic signal path 330 (FIG. 8).
11
The second ultrasonic signal path 320 is initially directed at a 10 degree angle
122 from a center location 121 along the back wall 175 ofthe ftrst ultrasonic buffer 172.
This second ultrasonic signal path 320 changes direction at the face 176 of the ftrst
ultrasonic buffer 172, where it refracts into the fluid 192. This second ultrasonic signal
path 320 changes direction at the face 386 ofthe third ultrasonic buffer 382 where it
refracts from the fluid 192 into the third ultrasonic buffer 382. The second ultrasonic
signal path 320 changes direction again when it reflects off the lower wall 387 of the
third ultrasonic buffer 382. The second ultrasonic signal path 320 changes direction
again when it reflects off the straight line edge 398 or upper wall ofthe third ultrasonic
buffer 382. The second ultrasonic signal path 320 exits the second ultrasonic buffer 382
along the back wall 385 of the third ultrasonic buffer 382 and is received by the second
ultrasonic transducer 184. As shown, the second ultrasonic signal path 320 is longer than
the ftrst ultrasonic signal path 310.
FIG. 8 illustrates a plurality of ultrasonic signal paths 310, 330 traveling from
the ftrst ultrasonic buffer 172 (FIG. 2) to the third ultrasonic buffer 382 of FIGS. 6, as
seen from a second perspective. The third ultrasonic buffer 382 is shown where the
second dimension 399 is the distance between the lower wall 387 and the upper wall 388
of the third ultrasonic buffer 382. Relative to FIG. 7, the third ultrasonic buffer 382 has
been rotated 90 degrees.
The third ultrasonic signal path 330 is initially directed at a 10 degree angle
122 from a center location 121 along the back wall 175 ofthe ftrst ultrasonic buffer 172.
This third ultrasonic signal path 330 changes direction at the face 176 ofthe ftrst
ultrasonic buffer 172, where it refracts into the fluid 192. This third ultrasonic signal
path 330 changes direction at the face 386 ofthe third ultrasonic buffer 382 where it
refracts from the fluid 192 into the third ultrasonic buffer 382. The third ultrasonic signal
path 330 changes direction again when it reflects off the lower wall 387 ofthe third
ultrasonic buffer 382. The third ultrasonic signal path 330 changes direction again when
it reflects off the or upper wall 388 of the third ultrasonic buffer 382. The third ultrasonic
12
signal path 330 exits the third ultrasonic buffer 382 along the back wall 385 of the third
ultrasonic buffer 382 and is received by the second ultrasonic transducer 184. As shown,
the third ultrasonic signal path 330 is longer than the first ultrasonic signal path 310, and
is slightly longer than the second ultrasonic signal path 320.
FIG. 9 illustrates a plurality of received ultrasonic signal waveforms 410, 420,
430 corresponding to the ultrasonic signal as it is received by the second ultrasonic
transducer 184 via each ofthe ultrasonic signal paths 310, 320, 330 of FIGS. 7-8. Each
ultrasonic signal waveform 410,420,430 is a representative portion ofthe ultrasonic
signal. As shown, the first ultrasonic signal waveform 410 is received via the first
ultrasonic signal path 310, the second ultrasonic signal waveform 420 is received via the
second ultrasonic signal path 320, and the third ultrasonic signal waveform 430 is
received via the third ultrasonic signal path 330. The fourth (combined) ultrasonic signal
waveform 440 is the combination ofthe ultrasonic signal paths 310, 320, 330.
Each of the ultrasonic signal waveforms 410, 420, 430, respectively includes a
leading edge 412, 422, 432 that arrives at a particular time. In one exemplary ultrasonic
flow measurement system (1 MHz ultrasonic signal, the first ultrasonic buffer 172 and
the third ultrasonic buffer 382 are made from SS316 stainless steel, each 0.75 in. (19.05
mm) length, with 1.0 in. (25.4 mm) water separation between the ultrasonic buffers 172,
382), the leading edge 412 ofthe first ultrasonic signal waveform 410 is received by the
second ultrasonic transducer 184 via the first ultrasonic signal path 310 at a time of 23.53
microseconds. The leading edge 422 of the second ultrasonic signal waveform 420 is
received via the second ultrasonic signal path 320 at a time of27.12 microseconds. The
leading edge 432 ofthe third ultrasonic signal waveform 430 is received via the third
ultrasonic signal path 330 at a time of27.61 microseconds, different than the time of the
leading edge 422 of the second ultrasonic signal waveform 420 because ofthe different
cross-sections ofthe ultrasonic buffers 172,382.
The first portion 414 ofthe combined ultrasonic signal waveform 440 is the
portion of the received ultrasonic signal contributed by the first ultrasonic signal
13
wavefonn 410 received via the fIrst ultrasonic signal path 410 from which the transit time
should be determined. Since the second and third ultrasonic signal waveforms 420, 430
arrive at different times that are approximately one half cycle/period apart (0.5
microseconds for a 1 MHz signal), the destructive combination ofthese ultrasonic signal
wavefonns 420, 430 forms a second portion 444 ofthe combined ultrasonic signal
wavefonn 440 that has a smaller amplitude than the fIrst portion 414 of the combined
ultrasonic signal wavefonn 440. Since the amplitude ofthe second portion 444 is smaller
than the amplitude ofthe fIrst portion 414 of the combined ultrasonic signal wavefonn
440, the signal processing electronics ofthe ultrasonic flow measurement system can
more easily identify the fIrst portion 414 of the combined ultrasonic signal wavefonn 440
from which the transit time ofthe ultrasonic signal is determined.
FIG. 10 illustrates a cross sectional view of an exemplary fourth ultrasonic
buffer 582. Comparing FIG. 2 with FIG. 10 shows that the cross section ofthe fIrst
ultrasonic buffer 172 is different than the cross section ofthe fourth ultrasonic buffer 582.
As shown, the fourth ultrasonic buffer 582 has a diameter 599 of 0.427 inches (10.5
millimeters), which is smaller than the diameter 179 ofthe fIrst ultrasonic buffer 172,
which is 0.5 inches (12.7 millimeters).
FIG. 11 illustrates a plurality of ultrasonic signal paths 510, 520, 530 traveling
from the fIrst ultrasonic buffer 172 (FIG. 2) to the fourth ultrasonic buffer 582 of FIG. 10.
The ultrasonic signal is transmitted from the fIrst transducer 174 via the fIrst ultrasonic
buffer 172 to the second transducer 184 via the fourth ultrasonic buffer 582. A portion of
the ultrasonic signal is transmitted along a fIrst (main) ultrasonic signal path 510, which
is co-axial with axis 150 of FIG. 1. This fIrst ultrasonic signal path 510 is a straight and
direct path from the fIrst ultrasonic buffer 172 to the fourth ultrasonic buffer 582. As a
result of beam spread ofthe ultrasonic signal, angular components of the ultrasonic signal
travel along many other ultrasonic signal paths in addition to the fIrst ultrasonic signal
path 510. For example, a portion of the ultrasonic signal also travels along a second
ultrasonic signal path 520 and a third ultrasonic signal path 530.
14
The second ultrasonic signal path 520 is initially directed at a 10 degree angle
122 from a center location 121 along the back wall 175 ofthe frrst ultrasonic buffer 172.
This second ultrasonic signal path 520 changes direction at the face 176 ofthe first
ultrasonic buffer 172, where it refracts into the fluid 192. This second ultrasonic signal
path 520 changes direction at the face 586 ofthe fourth ultrasonic buffer 582 where it
refracts from the fluid 192 into the fourth ultrasonic buffer 582. The second ultrasonic
signal path 520 changes direction again when it reflects off the lower wall 587 of the
fourth ultrasonic buffer 582. The second ultrasonic signal path 520 changes direction
again when it reflects off the upper wall 588 ofthe third ultrasonic buffer 582. The
second ultrasonic signal path 520 exits the fourth ultrasonic buffer 582 along the back
wall 585 of the fourth ultrasonic buffer 582 and is received by the second ultrasonic
transducer 184. As shown, the second ultrasonic signal path 520 is longer than the first
ultrasonic signal path 510.
The third ultrasonic signal path 530 is initially directed at a 10 degree angle
132 from a non-center location 131 along the back wall 175 ofthe frrst ultrasonic buffer
172. The second ultrasonic signal path 530 changes direction when it reflects off the
lower wall 177 ofthe frrst ultrasonic buffer 172. The third ultrasonic signal path 530
changes direction and reflects off an upper wall 178 of the first ultrasonic buffer 172.
Next, the third ultrasonic signal path 530 changes direction at the face 176 of the first
ultrasonic buffer 172, where it refracts into the fluid 192. The third ultrasonic signal path
530 changes direction at the face 586 ofthe fourth ultrasonic buffer 582 where it refracts
from the fluid 192 into the fourth ultrasonic buffer 582. The third ultrasonic signal path
530 exits the fourth ultrasonic buffer 582 along the back wall 585 ofthe fourth ultrasonic
buffer 582 and is received by the second ultrasonic transducer 184. As shown, the
ultrasonic signal path 530 is longer than the first ultrasonic signal path 510, and is slightly
longer than the second ultrasonic signal path 520.
FIG. 12 illustrates a plurality of received ultrasonic signal waveforms 610,
620, 630 corresponding to the ultrasonic signal as it is received by the second ultrasonic
15
transducer 184 via the ultrasonic signal paths 510,520,530 ofFIG. 11. Each ultrasonic
signal waveform 610,620,630 is a representative portion of the ultrasonic signal. As
shown, the first ultrasonic signal waveform 610 is received via the first ultrasonic signal
path 510, the second ultrasonic signal waveform 620 is received via the second ultrasonic
signal path 520, and the third ultrasonic signal waveform 630 is received via the third
ultrasonic signal path 530. The fourth (combined) ultrasonic signal waveform 640 is the
combination ofthe ultrasonic signal paths 510, 520, 530.
Each ofthe ultrasonic signal waveforms 610, 620, 630, respectively includes a
leading edge 612, 622, 632 that arrives at a particular time. In one exemplary ultrasonic
flow measurement system (1 MHz ultrasonic signal, the first ultrasonic buffer 172 aIid
the fourth ultrasonic buffer 582 are made from SS316 stainless steel, each 0.75 in. (19.05
mm) length, with 1.0 in. (25.4 mm) water separation between the ultrasonic buffers 172,
582), the leading edge 612 of the first ultrasonic signal waveform 610 is received by the
second ultrasonic transducer 184 via the first ultrasonic signal path 510 at a time of23.53
microseconds. The leading edge 622 of the second ultrasonic signal waveform 620 is
received via the second ultrasonic signal path 520 at a time of 26.61 microseconds. The
leading edge 632 ofthe third ultrasonic signal waveform 630 is received via the third
ultrasonic signal path 530 at a time of27.12 microseconds, different than the time ofthe
leading edge 622 of the second ultrasonic signal waveform 620 because ofthe different
cross-sections of the ultrasonic buffers 172,582.
The first portion 614 ofthe combined ultrasonic signal waveform 640 is the
portion ofthe received ultrasonic signal contributed by the first ultrasonic signal
waveform 610 received via the first ultrasonic signal path 510 from which the transit time
should be determined. Since the second and third ultrasonic signal waveforms 620, 630
arrive at different times that are approximately one half cycle/period apart (0.5
microseconds for a 1 MHz signal), the destructive combination ofthese ultrasonic signal
waveforms 620, 630 forms a second portion 644 ofthe combined ultrasonic signal
waveform 640 that has a smaller amplitude than the first portion 614 of the combined
16
ultrasonic signal waveform 640. Since the amplitude ofthe second portion 644 is smaller
than the amplitude ofthe first portion 614 of the combined ultrasonic signal waveform
640, the signal processing electronics of the ultrasonic flow measurement system can
more easily identify the first portion 614 ofthe combined ultrasonic signal waveform 640
from which the transit time of the ultrasonic signal is determined.
FIG. 13 illustrates a cross sectional view of an exemplary fifth ultrasonic
buffer 782. Comparing FIG. 2 with FIG. 13 shows that the cross section ofthe first
ultrasonic buffer 172 is slightly different than the cross section ofthe fifth ultrasonic
buffer 782. As shown, the fifth ultrasonic buffer 782 has a diameter 799 of 0.51 inches
(12.95 millimeters), which is slightly larger than the diameter 179 ofthe first ultrasonic
buffer 172, which is 0.50 inches (12.7 millimeters). Further, in this embodiment, the first
ultrasonic buffer 172 is here made from Molybdenum and the fifth ultrasonic buffer 782
is made from SS316 stainless steel. It will be understood that other materials can be used
for the ultrasonic buffers, which may result in the use of different diameters for those
buffers.
FIG. 14 illustrates a plurality of ultrasonic signal paths 710, 720, 730 traveling
from the first ultrasonic buffer 172 (FIG. 2) to the fifth ultrasonic buffer 782 of FIG. 13.
The ultrasonic signal is transmitted from the first transducer 174 via the first ultrasonic
buffer 172 to the second transducer 184 via the fifth ultrasonic buffer 782. A portion of
the ultrasonic signal is transmitted along a first (main) ultrasonic signal path 710, which
is co-axial with axis 150 of FIG. 1. This first ultrasonic signal path 710 is a straight and
direct path from the first ultrasonic buffer 172 (FIG. 2) to the fifth ultrasonic buffer 782.
As a result of beam spread of the ultrasonic signal, other angular components of the
ultrasonic signal travel along many other ultrasonic signal paths in addition to the first
ultrasonic signal path 710. For example, a portion of the ultrasonic signal also travels
along a second ultrasonic signal path 720 and a third ultrasonic path 730.
The second ultrasonic signal path 720 is initially directed at a 10 degree angle
122 from a center location 121 along the back wall 175 ofthe first ultrasonic buffer 172.
17
The second ultrasonic signal path 720 changes direction at the face 176 ofthe first
ultrasonic buffer 172, where it refracts into the fluid 192. The second ultrasonic signal
path 720 changes direction at the face 786 ofthe fifth ultrasonic buffer 782 where it
refracts from the fluid 192 into the fifth ultrasonic buffer 782. The second ultrasonic
signal path 720 changes direction again when it reflects off the lower wall 787 ofthe fifth
ultrasonic buffer 782. The second ultrasonic signal path 720 changes direction again
when it reflects off the upper wall 788 ofthe fifth ultrasonic buffer 782. The second
ultrasonic signal path 720 exits the fifth ultrasonic buffer 782 along the back wall 785 of
the fifth ultrasonic buffer 782 and is received by the second ultrasonic transducer 184.
As shown, the second ultrasonic signal path 720 is longer than the first ultrasonic signal
path 710.
The third ultrasonic signal path 730 is initially directed at a 10 degree angle
132 from a non-center location 131 along the back wall 175 of the first ultrasonic buffer
172. The third ultrasonic signal path 730 changes direction when it reflects off the lower
wall 177 of the first ultrasonic buffer 172. The third ultrasonic signal path 730 changes
direction and reflects off an upper wall 178 ofthe first ultrasonic buffer 172. Next, the
third ultrasonic signal path 730 changes direction at the face 176 of the first ultrasonic
buffer 172, where it refracts into the fluid 192. The third ultrasonic signal path 730
changes direction at the face 786 ofthe fifth ultrasonic buffer 782 where it refracts from
the fluid 192 into the fifth ultrasonic buffer 782. The third ultrasonic signal path 730
exits the fifth ultrasonic buffer 782 along the back wall 785 of the fifth ultrasonic buffer
782 and is received by the second ultrasonic transducer 184. As shown, the third
ultrasonic signal path 730 is longer than the first ultrasonic signal path 710, and is slightly
shorter than the second ultrasonic signal path 720.
FIG. 15 illustrates a plurality of received ultrasonic signal waveforms 810,
820, 830 corresponding to the ultrasonic signal as it is received by the second transducer
184 via each ofthe ultrasonic signal paths 710, 720, 730 of FIG. 14. Each waveform
810,820,830 is a representative portion ofthe ultrasonic signal. As shown, the first
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ultrasonic signal waveform 810 is received via the fIrst ultrasonic signal path 710, the
second ultrasonic signal waveform 820 is received via the second ultrasonic signal path
720, and the third ultrasonic signal waveform 830 is received via the third ultrasonic
signal path 730. The fourth (combined) ultrasonic signal waveform 840 is the
combination ofthe ultrasonic signal paths 710, 720, 730.
Each ofthe ultrasonic signal waveforms 810, 820, 830, respectively includes a
leading edge 812,822,832 that arrives at a particular time. In one exemplary ultrasonic
flow measurement system (1 MHz ultrasonic signal, the fIrst ultrasonic buffer 172 is
made from Molybdenum and the fIfth ultrasonic buffer 782 is made from SS316 stainless
steel, each are 0.75 in. (19.05 rom) length, with 1.0 in. (25.4 rom) water separation
between the ultrasonic buffers 172, 782), the leading edge 812 of the fIrst ultrasonic
signal waveform 710 is received by the second ultrasonic transducer 184 via the fIrst
ultrasonic signal path 710 at a time of23.17 microseconds. The leading edge 822 ofthe
second ultrasonic signal waveform 820 is received via the second ultrasonic signal path
720 at a time of 26.82 microseconds. The leading edge 832 of the third ultrasonic signal
waveform 830 is received via the third ultrasonic signal path 730 at a time of26.30
microseconds, different than the time of the leading edge 822 ofthe second ultrasonic
signal waveform 820 because ofthe different cross-sections and materials of the
ultrasonic buffers 172, 782.
The fIrst portion 814 ofthe combined ultrasonic signal waveform 840 is the
portion of the received ultrasonic signal contributed by the fIrst ultrasonic signal
waveform 810 received via the fIrst ultrasonic signal path 710 from which the transit time
should be determined. Since the second and third ultrasonic signal waveforms 820, 830
arrive at different times that are approximately one half cycle/period apart (0.5
microseconds for a 1 MHz signal), the destructive combination ofthese ultrasonic signal
waveforms 820, 830 forms a second portion 844 ofthe combined ultrasonic signal
waveform 840 that has a smaller amplitude than the fIrst portion 814 of the combined
ultrasonic signal waveform 840. Since the amplitude ofthe second portion 844 is smaller
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than the amplitude ofthe fIrst portion 814 of the combined ultrasonic signal waveform
840, the signal processing electronics ofthe ultrasonic flow measurement system can
more easily identify the fIrst portion 814 ofthe combined ultrasonic signal waveform 840
from which the transit time ofthe ultrasonic signal is determined.
This written description uses examples to disclose the invention, including
the best mode, and also to enable any person skilled in the art to practice the invention,
including making and using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defmed by the claims, and may
include other examples that occur to those skilled in the art. Such other examples are
intended to be within the scope ofthe claims ifthey have structural elements that do not
differ from the literal language ofthe claims, or if they include equivalent structural
elements with insubstantial differences from the literal language ofthe claims. For
example, while the fIrst section and second section ofthe cap are shown disposed
substantially planar to the fIrst planar surface of the substrate in the disclosed
embodiments, it will be understood that the sections can be disposed at a different
orientation (e.g., at a slope relative to the fIrst planar surface ofthe substrate).
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•
ULTRASONIC FLOW MEASUREMENT SYSTEM
PARTS LIST:
100 exemplary ultrasonic flow sensing system
110 fIrst (main)ultrasonic signal path
120 second ultrasonic signal path
121 center location
122 angle
130 third ultrasonic signal path
131 non-center location
132 angle
150 axis
170 fIrst ultrasonic sensor
172 fIrst ultrasonic buffer
173 cross section of fIrst ultrasonic buffer 172
174 fIrst ultrasonic transducer
175 back side ofultrasonic buffer 172
176 face of ultrasonic buffer 172
177 lower wall ofultrasonic buffer 172
178 upper wall ofultrasonic buffer 172
179 diameter of fIrst ultrasonic buffer 172
180 second ultrasonic sensor
182 second ultrasonic buffer
183 cross section ofsecond ultrasonic buffer 182
184 second ultrasonic transducer
185 back side ofultrasonic buffer 182
186 face ofultrasonic buffer 182
187 lower wall ofultrasonic buffer 182
188 upper wall ofultrasonic buffer 182
189 diameter of second ultrasonic buffer 182
190 pipe
192 fluid
210 fIrst ultrasonic signal waveform
212 leading edge of fust ultrasonic signal waveform 210
214 fIrst portion of combined ultrasonic signal waveform 240
220 second ultrasonic signal waveform
222 leading edge of second ultrasonic signal waveform 220
230 third ultrasonic signal waveform
232 leading edge ofthird ultrasonic signal waveform 230
240 fourth (combined) ultrasonic signal waveform
244 second portion of fourth (combined) ultrasonic signal waveform 240
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310 first (main) ultrasonic signal path
320 second ultrasonic signal path
330 third ultrasonic signal path
382 third ultrasonic buffer
383 first section
384 second section
397 first dimension ofthird ultrasonic buffer 382
398 straight line edge ofthird ultrasonic buffer 382
399 second dimension of third ultrasonic buffer 382
410 first ultrasonic signal waveform
412 leading edge offirst ultrasonic signal waveform 410
414 first portion of fourth (combined) ultrasonic signal waveform 440
420 second ultrasonic signal waveform
422 leading edge of second ultrasonic signal waveform 420
430 third ultrasonic signal waveform
432 leading edge ofthird ultrasonic signal waveform 430
440 fourth (combined) ultrasonic signal waveform
444 second portion of combined ultrasonic signal waveform 440
510 first (main) ultrasonic signal path
520 second ultrasonic signal path
530 third ultrasonic signal path
582 fourth ultrasonic buffer
583 cross section of fourth ultrasonic buffer 582
599 diameter offourth ultrasonic buffer 582
610 first ultrasonic signal waveform
612 leading edge of frrst ultrasonic signal waveform 610
614 first portion of combined ultrasonic signal waveform 640
620 second ultrasonic signal waveform
622 leading edge of second ultrasonic signal waveform 620
630 third ultrasonic signal waveform
632 leading edge of third ultrasonic signal waveform 630
640 fourth (combined) ultrasonic signal waveform
644 second portion 644 of fourth (combined) ultrasonic signal waveform 640
710 first (main) ultrasonic signal path
720 second ultrasonic signal path
730 third ultrasonic signal path
782 fifth ultrasonic buffer
783 cross section of fifth ultrasonic buffer 582
799 diameter of fifth ultrasonic buffer 782
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810 first ultrasonic signal waveform
812 leading edge offirst ultrasonic signal waveform 810
814 first portion of combined ultrasonic signal waveform 840
820 second ultrasonic signal waveform
822 leading edge of second ultrasonic signal waveform 820
830 third ultrasonic signal waveform
832 leading edge ofthird ultrasonic signal waveform 830
840 fourth (combined) ultrasonic signal waveform
844 second portion 844 of combined ultrasonic signal waveform 840

•
We Claims:
1. An ultrasonic flow measurement system comprising:
a first ultrasonic sensor comprising a first ultrasonic transducer and a first
ultrasonic buffer; and
a second ultrasonic sensor comprising a second ultrasonic transducer and a second
ultrasonic buffer, the second ultrasonic sensor is aligned with the frrst ultrasonic sensor
along an axis,
wherein the frrst ultrasonic buffer has a frrst cross section that is perpendicular to
the axis and the second ultrasonic buffer has a second cross section that is perpendicular
to the axis, and
wherein the frrst cross section ofthe first ultrasonic buffer is different from the
second cross section of the second ultrasonic buffer.
2. The ultrasonic flow measurement system of claim I, wherein the frrst
cross section of the frrst ultrasonic buffer has a frrst shape and the second cross section of
the second ultrasonic buffer has a second shape, and wherein the first shape is different
from the second shape.
3. The ultrasonic flow measurement system of claim 1, wherein the first
cross section of the first ultrasonic buffer has a circular shape and the second cross
section ofthe second ultrasonic buffer has a first section having a circular shape and a
second section having a straight edge.
4. The ultrasonic flow measurement system of claim 1, wherein the first
cross section ofthe first ultrasonic buffer has a frrst diameter and the second cross section
of the second ultrasonic buffer has a second diameter, and wherein the first diameter is
different from the second diameter.
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•
5. The ultrasonic flow measurement system of claim I, wherein the first
diameter is larger than the second diameter.
6. The ultrasonic flow measurement system of claim 4, wherein the first
ultrasonic buffer is constructed from a first material and the second ultrasonic buffer is
constructed from a second material, and wherein the first material is different from the
second material.
7. The ultrasonic flow measurement system of claim 6 wherein the first
material is Molybdenum and the second material is stainless steel.
8. An ultrasonic flow measurement system comprising:
a first ultrasonic sensor comprising a first ultrasonic transducer and a first
ultrasonic buffer; and
a second ultrasonic sensor comprising a second ultrasonic transducer and a second
ultrasonic buffer, the second ultrasonic sensor is aligned with the first ultrasonic sensor
along an axis,
wherein the first ultrasonic buffer has a first cross section that is perpendicular to
the axis and the second ultrasonic buffer has a second cross section that is perpendicular
to the axis, and
wherein the first cross section of the first ultrasonic buffer has a first shape and
the second cross section ofthe second ultrasonic buffer has a second shape, and wherein
the first shape is different from the second shape.
9. The ultrasonic flow measurement system of claim 8, wherein the first
cross section of the first ultrasonic buffer has a circular shape and the second cross
section of the second ultrasonic buffer has a first section having a circular shape and a
second section having a straight edge.
25
•
10. An ultrasonic flow measurement system comprising:
a first ultrasonic sensor comprising a first ultrasonic transducer and a first
ultrasonic buffer; and
a second ultrasonic sensor comprising a second ultrasonic transducer and a second
ultrasonic buffer, the second ultrasonic sensor is aligned with the first ultrasonic sensor
along an axis,
wherein the first ultrasonic buffer has a first cross section that is perpendicular to
the axis and the second ultrasonic buffer has a second cross section that is perpendicular
to the axis, and
wherein the first cross section ofthe first ultrasonic buffer has a first diameter and
the second cross section ofthe second ultrasonic buffer has a second diameter, and
wherein the first diameter is different from the second diameter.
11. The ultrasonic flow measurement system of claim 10, wherein the first
diameter is larger than the second diameter.
12. The ultrasonic flow measurement system of claim 10, wherein the first
cross section of the first ultrasonic buffer has a circular shape and the second cross
section of the second ultrasonic buffer has a first section having a circular shape and a
second section having a straight edge.
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ANISHA SI H NAIR
Agent for the Applicant [IN/PA-740]
LEX ORBIS
Intellectual Property Practice
709/710, Tolstoy House,
15-17, T31stoy Marg,
New Delhi-IIOOOl
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