U.S. patent application number 10/658583 was filed with the patent office on 2004-03-11 for determining levels of substances using multistatic probes.
Invention is credited to Champion, James Robert, Brien II Evans, John O?apos, Schenk, William Peters JR..
Application Number | 20040046572 10/658583 |
Document ID | / |
Family ID | 31978749 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040046572 |
Kind Code |
A1 |
Champion, James Robert ; et
al. |
March 11, 2004 |
Determining levels of substances using multistatic probes
Abstract
The disclosed technology pertains to multistatic probes that can
determine a level of one or more substances. A multistatic probe
can include transmitting and receiving conductive elements that are
electrically distinct and which are capable of conveying
electromagnetic energy in proximity to/from substances of interest.
The conductive elements can be arranged to be adjacent to a coupler
that is positioned at a dielectric mismatch boundary between
substances of interest, whereby an electromagnetic signal
transmitted on the transmitting conductive element causes a change
in capacitance in the transmitting conductive element upon the
electromagnetic signal traversing a part of the transmitting
conductive element substantially adjacent to the coupler, which
causes a corresponding electromagnetic signal to be coupled to the
receiving conductive element. Attributes of the received
electromagnetic signal can be evaluated relative to the transmitted
electromagnetic signal to determine a level associated with one or
more of the substances of interest.
Inventors: |
Champion, James Robert;
(Maryville, TN) ; Schenk, William Peters JR.;
(Rockford, TN) ; Evans, John O?apos;Brien II;
(Powell, TN) |
Correspondence
Address: |
FOLEY HOAG, LLP
PATENT GROUP, WORLD TRADE CENTER WEST
155 SEAPORT BLVD
BOSTON
MA
02110
US
|
Family ID: |
31978749 |
Appl. No.: |
10/658583 |
Filed: |
September 9, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60409360 |
Sep 9, 2002 |
|
|
|
Current U.S.
Class: |
324/637 |
Current CPC
Class: |
G01F 23/284 20130101;
G01F 23/76 20130101; G01F 23/68 20130101 |
Class at
Publication: |
324/637 |
International
Class: |
G01R 027/04; G01R
027/32 |
Claims
What is claimed is:
1. A system for determining a level of a substance, the system
comprising: a first conductive element conveying a first
electromagnetic signal in proximity to a plurality of substances; a
coupler positioned at a dielectric mismatch boundary between the
substances, the coupler causing a change in a capacitance of the
first conductive element upon the first electromagnetic signal
traversing a part of the first conductive element substantially
adjacent to the coupler; a second conductive element conveying a
second electromagnetic signal based on the first electromagnetic
signal and being coupled thereto by the change in capacitance of
the first conductive element caused by the coupler; and a processor
executing instructions to determine a level of at least one of the
substances based at least in part on a time delay between the first
and second electromagnetic signals.
2. The system of claim 1 wherein the first and second conductive
elements are positioned substantially parallel to each other and
substantially perpendicular to the dielectric mismatch
boundary.
3. The system of claim 1 wherein the first electromagnetic signal
exhibits an ultra-wideband frequency.
4. The system of claim 1 wherein the dielectric mismatch boundary
corresponds to a transitional region between a gaseous substance
and a liquid substance.
5. The system of claim 1 wherein the dielectric mismatch boundary
corresponds to a transitional region between at least two of a
vacuum, a gaseous substance, a liquid substance, a semi-solid
substance, and a solid substance.
6. The system of claim 1 further comprising a transmitter for
forming the first electromagnetic signal.
7. The system of claim 1 further comprising a receiver for
detecting the time delay between the first and second
electromagnetic signals.
8. The system of claim 7 wherein the receiver includes an
equivalent time sampling circuit.
9. The system of claim 1 wherein the first and second conductive
elements form a parallel conductor transmission line structure.
10. The system of claim 1 wherein the first and second conductive
elements are flexible.
11. The system of claim 1 wherein the first and second conductive
elements exhibit quadrilateral cross-sections.
12. The system of claim 1 wherein the first and second conductive
elements exhibit substantially identical cross-sections.
13. The system of claim 1 wherein an amplitude of the second
electromagnetic signal is substantially independent of dielectric
properties associated with the substances forming the dielectric
mismatch boundary.
14. The system of claim 1 wherein the coupler exhibits a length
corresponding to at least one-quarter of a propagation velocity
pulse length of the first electromagnetic signal.
15. The system of claim 1 further comprising: a float for
positioning the coupler at the dielectric mismatch boundary.
16. The system of claim 15 wherein the float includes a buoyant
component and a weighted component.
17. The system of claim 1 wherein the level corresponds to a volume
of fluid in an above-ground storage tank.
18. The system of claim 1 wherein the level corresponds to a volume
of fluid in a below-ground storage tank.
19. The system of claim 1 wherein the processor communicates the
substance level to a digital data processing device during a
communication session.
20. A method of determining a level of a substance, the method
comprising: transmitting a first electromagnetic signal on a first
conductive element, the first conductive element being in proximity
to a plurality of substances; providing a coupler positioned at a
dielectric mismatch boundary between the substances, the coupler
causing a change in a capacitance of the first conductive element
upon the first electromagnetic signal traversing a part of the
first conductive element substantially adjacent to the coupler;
receiving a second electromagnetic signal based on the first
electromagnetic signal at a second conductive element and in
response the change in capacitance of the first conductive element
caused by the coupler; and determining a level of at least one of
the substances based at least in part on a time delay between the
first and second electromagnetic signals.
21. The method of claim 20 wherein the first and second conductive
elements are flexible.
22. The method of claim 20 wherein the first and second conductive
elements are positioned substantially parallel to each other and
substantially perpendicular to the dielectric mismatch
boundary.
23. The method of claim 20 wherein an amplitude of the second
electromagnetic signal is independent of dielectric properties
associated with the substances forming the dielectric mismatch
boundary.
24. The method of claim 20 further comprising: providing a float
for positioning the coupler relative to the dielectric mismatch
boundary.
Description
CLAIM OF PRIORITY
[0001] This application claims priority to and the benefit of
United States Provisional Patent Application No. 60/409,360, filed
Sep. 9, 2002, the entirety of which is incorporated herein by
reference.
RELATED APPLICATIONS
[0002] This is also related to the following co-pending and
concurrently-filed U.S. Utility Patent Application Nos., the
entirety of which are incorporated herein by reference:
[0003] 10/_______, "Characterizing Substances With Multistatic
Probes," identified by Attorney Docket No. FOM-139.01; and
[0004] 10/_______, "Measuring Distances Using Multistatic Probes,"
identified by Attorney Docket No. FOM-139.03.
TECHNICAL FIELD
[0005] The disclosed technology relates generally to determining
characteristics of substances and more particularly to determining
such characteristics using multistatic probes.
BACKGROUND
[0006] Detecting the presence and characteristics of particular
substances and/or combinations of substances that are difficult to
inspect can provide entities interested in the control and
monitoring of such substances with information critical to those
entities' operations. Technology capable of such detection and
characterization finds applicability in many areas, such as in,
linear displacement measurement devices, position measurement,
pressure analysis, land mine detection, fluid/soil contamination,
fluid/gas level detection, substance composition analysis,
geological mapping/imaging, and in a myriad of storage, monitoring,
and processing applications.
[0007] The technologies that have been developed and applied to
such detection and characterization are as diverse as their
applications and include, for example, mechanical/electromechanical
sensors (e.g., floats), sonic/ultrasonic sensors, radar (e.g.,
ground penetrating radar), time domain reflectometry sensors
("TDR"), x-ray sensors, capacitive level sensors, etc. These
technologies can exhibit shortcomings that mitigate their
usefulness such as, for example, floats that can be unreliable
particularly in multi-fluid and/or corrosive environments;
sonic/ultrasonic sensors whose acoustic signals may reflect off of
foamy material or container walls and fail to capture fluidic
surfaces and boundaries; radar sensors may be expensive, complex,
bulky, and/or may exhibit limited resolution; TDR sensors may
exhibit excessive ringing and thereby limit short range detection
and may require different designs when used with different
dielectric substances due to changes in reflection amplitude; x-ray
sensors may fail to differentiate between similar substances; and
capacitive level sensors may not operate accurately due to
nonlinear dielectric properties of a substance and may fail to
provide desirable information about a particular mixture.
Accordingly, entities interested in residential, commercial,
industrial, medical, scientific, military, and/or other
applications of substance characterization technology have a
continuing interest in further developing these technologies to
more accurately and flexibly meet their control and monitoring
objectives.
SUMMARY
[0008] The disclosed technology can be used in the development and
operation of multistatic sensor probes that can characterize
substances and relationships between substances. A multistatic
probe can include transmitting and receiving conductive elements
that are physically and/or electrically distinct and which are
capable of conveying electromagnetic energy to/from a substance of
interest. The transmitting and receiving conductive elements can be
arranged so as to be in contact with at least one dielectric
mismatch boundary associated with substances of interest, whereby
an electromagnetic signal transmitted on the transmitting
conductive element causes a corresponding electromagnetic signal to
be conveyed on the receiving conductive element in response to the
transmitted signal being in proximity to the dielectric mismatch
boundary. Attributes of the received electromagnetic signal can be
evaluated relative to the transmitted electromagnetic signal to
determine one or more characteristics associated with at least one
of the substances forming the dielectric mismatch boundary.
[0009] In one embodiment, the disclosed technology can be used to
develop systems and perform methods in which an electromagnetic
signal (exhibiting, for example, an ultra-wideband frequency) is
formed and transmitted by a transmitter via one or more first
conductive elements that are in contact with one or more dielectric
mismatch boundaries, which correspond to transitional surfaces
and/or regions associated with substances of interest that exhibit
different dielectric constants, such as may be associated with two
or more gaseous substances, vacuums, liquid substances, semi-solid
substances, and/or solid substances. An electromagnetic signal
based on the transmitted signal can be coupled to one or more
second conductive elements (that can also be in contact with the
dielectric mismatch boundaries) in response to the dielectric
mismatch boundary and can be subsequently received by a receiver.
The at least one first and second conductive elements can be
arranged to form a parallel conductor transmission line structure,
manufactured from flexible material to enable the conductive
elements to substantially reform into a desirable
shape/configuration, and/or exhibit substantially identical
cross-sections (e.g., quadrilateral). A processing clement can
evaluate attributes (e.g., a time delay determined using an
equivalent time sampling circuit) of the received electromagnetic
signal relative to the transmitted electromagnetic signal to
determine characteristics (e.g., level and/or volume of a fluid in
an above-ground or below-ground storage tank) of one or more
substances associated with the dielectric mismatch boundary. The
processing element can also communicate one or more of the
attributes of the received electromagnetic signal and/or one or
more of the characteristics of the substances associated with the
dielectric mismatch boundary to a local and/or remote digital data
processing device during a communication session.
[0010] In one embodiment, a third conductive element connected to a
ground plane can surround at least part of the at least one first
and second conductive elements. The at least one first and second
conductive elements can also be positioned substantially parallel
to each other and substantially perpendicular to the at least one
dielectric mismatch boundary.
[0011] In one embodiment, the disclosed technology can include a
coupler that can operate as an electromagnetic shunt path between
the at least one first and second conductive elements and can be
positioned at the dielectric mismatch boundary for coupling the
received electromagnetic signal independently of the dielectric
properties associated with the substances forming the dielectric
mismatch boundary. The coupler can, for example, exhibit a length
corresponding to at least one-quarter of a propagation velocity
pulse length of the transmitted electromagnetic signal. A float
including a buoyant and/or a weighted component can also be
provided to position the coupler relative to the at least one
dielectric mismatch boundary.
[0012] In one embodiment, the disclosed technology can be used to
develop systems and to perform methods for determining levels
and/or volumes of substances (e.g., fluids) that may be contained
in, for example, above-ground or below-ground storage tanks or
other types of containers. A first electromagnetic signal
(exhibiting, for example, an ultra-wideband frequency) can be
formed by a transmitter and conveyed on a first conductive element
that is positioned in proximity to one or more substances. When the
first electromagnetic signal traverses a part of the first
conductive element that is substantially adjacent to a coupler
positioned at a dielectric mismatch boundary (e.g., a transitional
surface and/or region between a vacuum, a gaseous substance, a
liquid substance, a semi-solid substance, and/or a solid
substance), a resulting change in the capacitance of the first
conductive element can cause a coupling of a second electromagnetic
signal (which can be, for example, based on the first
electromagnetic signal) to a second conductive element. The
amplitude of the second electromagnetic signal can be based on the
dielectric properties of the coupler and thus can be independent of
the dielectric properties associated with the substances forming
the dielectric mismatch boundary. In one embodiment, the coupler
can exhibit a length corresponding to at least one-quarter of a
propagation velocity pulse length of the first electromagnetic
signal. A processor can determine a level and/or volume of at least
one of the substances based at least in part on a time delay
between the first and second electromagnetic signals that can be
detected by a receiver using, for example, an equivalent time
sampling circuit. The processor can further communicate one or more
substance levels, volumes, and/or other attributes to a local
and/or remote digital data processing device via a data
communications network.
[0013] In one embodiment, the first and second conductive elements
can be positioned substantially parallel to each other and
substantially perpendicular to the dielectric mismatch boundary. In
one embodiment, the first and second conductive elements can also
be flexible, form a parallel conductor transmission line structure,
and/or exhibit substantially identical cross-sections (e.g.,
quadrilateral). In one embodiment, the disclosed technology can use
a float to position the coupler at the dielectric mismatch
boundary. The float can include a buoyant component and/or a
weighted component.
[0014] In one embodiment, the disclosed technology can be used to
develop systems and to perform methods for measuring distances
between points of interest that can be associated with one or more
objects. A first electromagnetic signal (exhibiting, for example,
an ultra-wideband frequency), formed by a transmitter and conveyed
on a first conductive element, can traverse a part of the first
conductive element that is substantially adjacent to a coupler
positioned at a point of interest, thereby resulting in an increase
in capacitance between the first conductive element and a second
conductive element along portions of these conductive elements
adjacent to the coupler. The increased capacitance between these
portions of the first and second conductive elements causes a
second electromagnetic signal based on the first electromagnetic
signal to be coupled to the second conductive element that is
otherwise physically and/or electrically distinct from the first
conductive element. In one embodiment, the coupler can exhibit a
length corresponding to at least one-quarter of a propagation
velocity pulse length of the first electromagnetic signal. A
processor can execute instructions to determine a distance
associated with the point of interest based at least in part on a
time delay between the first and second electromagnetic signals
that can be detected by a receiver using, for example, an
equivalent time sampling circuit. The distance can correspond to,
for example, a dimension associated with an object, a displacement
between objects, an angular orientation, and/or a degree of
pressure. The processor can further communicate the distance and/or
data based thereon to a local and/or remote digital data processing
device during a communication session.
[0015] In one embodiment, the first and second conductive elements
can be flexible, form a parallel conductor transmission line
structure, and/or exhibit substantially identical cross-sections
(e.g., quadrilateral). In one embodiment, the disclosed technology
can also provide for a supporting material that can slidably
receive the coupler in a channel defined therein and this
supporting material can maintain a consistent displacement between
the coupler and the first and second conductive elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The foregoing discussion will be understood more readily
from the following detailed description of the disclosed
technology, when taken in conjunction with the accompanying
drawings in which:
[0017] FIG. 1 illustrates exemplary waveforms of electromagnetic
signals that may be encountered during the operation of multistatic
and TDR probe systems;
[0018] FIG. 2 schematically illustrates exemplary elements of a
multistatic probe system;
[0019] FIG. 3 illustrates an exemplary embodiment of a parallel
coplanar strip transmission line that may be used as an element of
the multistatic probe system of FIG. 2;
[0020] FIG. 4 illustrates an exemplary methodology that may be
preformed during the operation of the multistatic probe system of
FIG. 2;
[0021] FIG. 5 illustrates exemplary waveforms of electromagnetic
signals that may be encountered during the operation of multistatic
probe systems, in the absence of and in the presence of
couplers;
[0022] FIG. 6A schematically illustrates an exemplary use of a
float, a coupler, and/or a weight with the multistatic probe system
of FIG. 2;
[0023] FIG. 6B schematically illustrates exemplary cross-sections
of the coupler of FIG. 6A when used with the transmission line
structure of FIG. 3;
[0024] FIG. 7A schematically illustrates an exemplary embodiment of
a multistatic probe system when used as a linear distance
measurement device; and
[0025] FIG. 7B schematically illustrates an exemplary cross-section
of the linear distance measurement device of FIG. 7A.
DETAILED DESCRIPTION
[0026] Unless otherwise specified, the illustrated embodiments can
be understood as providing exemplary features of varying detail of
certain embodiments, and therefore, unless otherwise specified,
features, components, processes, modules, data elements, and/or
aspects of the illustrations can be otherwise combined,
interconnected, sequenced, separated, interchanged, and/or
rearranged without departing from the disclosed systems or methods.
Additionally, the shapes, sizes, and orientations of elements are
also exemplary and unless otherwise specified, can be altered
without affecting the disclosed technology.
[0027] For the purposes of this disclosure, the term
"substantially" can be broadly construed to indicate a precise
relationship, condition, arrangement, orientation, and/or other
characteristic, as well as, deviations thereof as understood by one
of ordinary skill in the art, to the extent that such deviations do
not materially affect the disclosed methods and systems.
[0028] Time Domain Reflectometry (TDR) refers to a technology that
has been applied in the characterization of substances and involves
transmitting an electromagnetic signal on a conductive element
(e.g., a transmission line) immersed in or otherwise in contact
with a substance of interest, while simultaneously monitoring the
same conductive element for corresponding electromagnetic signals
that are reflected along the conductive element. A conductive
element can be understood to be capable of conveying
electromagnetic signals and can be, for example, a structure of
substantially constant cross-section. Electromagnetic signals can
be reflected along the same conductive element in response to
changes in the conductive element's characteristics (e.g.,
impedance) that may be affected by substances that are in contact
with the conductive element at particular locations along its
length.
[0029] For example and with reference to the exemplary waveform 102
(labeled as W-TDR) measured on a typical TDR probe in FIG. 1, at
least part of an electromagnetic signal 104 transmitted on a
transmission line immersed in a tank or other container containing
air and a liquid (e.g., water) substance will be reflected along
the transmission line when the electromagnetic signal 104
encounters the change in the transmission line's impedance that
occurs above and below the dielectric mismatch boundary between the
air and the liquid. The amplitude of the reflected signal 106 is
related to the difference in impedance (referred to as a reflection
coefficient) and thus to a difference in the dielectric constants
of the substances forming the dielectric mismatch boundary. A
dielectric mismatch boundary can refer generally to a surface or
region between substances that exhibit different dielectric
constants. A dielectric constant of a substance can refer to a
measure of the ability of that substance to store energy in an
electric field relative to the permittivity of free space and can
therefore be used to identify and/or otherwise characterize a
substance of interest. Analysis of the time differential between
the transmitted and reflected electromagnetic signals 104, 106 can
be used to determine the location of the dielectric mismatch
boundary and can thus, for example, ascertain the level of the
liquid in the tank.
[0030] Similarly, substances in contact with the transmission line
can change the velocity of propagation of the electromagnetic
signal along the transmission line, which can be used to determine
not only the level of the substances, but also their dielectric
constants. A velocity of propagation can refer to a ratio of the
velocity of light to the square root of a product of the relative
permeability (capability of storing energy in a magnetic field) and
effective dielectric constant (expressed with respect to an
electric field associated with a signal on a non-shielded
transmission line) of the transmission line.
[0031] Unfortunately, TDR systems typically exhibit interference
(e.g., ringing, saturation, etc.) that may interfere with the
reception/measurement of the reflected signal 106, particularly in
situations where the location of the source of the transmitted
signal 104 is close to the dielectric mismatch boundary, due to
concurrent monitoring of the same transmission line by
receiver-side circuitry that is normally subjected directly to the
output of a transmitter-side circuit that produced the transmitted
electromagnetic signal 104. For example, if the location of the
transmitter-side circuitry and the dielectric mismatch boundary
were such that the reflected signal 106 occurred during an
interference zone 108, then the relatively small amplitude of the
reflected signal 106 may be insufficient to overcome the degree of
interference and thus the receiver-side circuitry may fail to
detect the reflected signal 106. Further, the design of a TDR
probe/device may limit the application of that device to specific
applications, thereby reducing the overall useability of the device
as substances, dielectric constants, and other environmental and/or
operational factors are changed.
[0032] The disclosed technology can reduce, if not eliminate, these
TDR shortcomings by using electrically-separate transmit and
receive conductive elements. Sensor probes that are constructed
with one or more transmit conductive elements that are
electrically-separate from one or more receive conductive elements
will hereinafter be referred to as being multistatic.
[0033] In brief overview and with reference to the exemplary
waveform 110 (labeled as W-Multistatic) measured on a receive
conductive element of an exemplary multistatic probe in FIG. 1, a
transmitter of a multistatic probe can produce an electromagnetic
signal (not shown) that is conveyed along the length of a transmit
conductive element. When the transmitted signal encounters a
dielectric mismatch boundary formed between substances in contact
with and/or otherwise adjacent to the transmit conductive element,
a resulting change in the capacitance between the transmit
conductive element and a receive conductive element (transmit and
receive conductive elements are electrically separate) causes at
least part of the transmitted signal to be coupled to the
electrically distinct, receive conductive element. Coupling of
electromagnetic energy between the transmit and receive conductive
elements corresponds to an amount of signal transfer action,
expressed, for example, as a coupling coefficient, that is at least
partly based on the spacing and impedances between the transmit and
receive conductive elements in the vicinity of the dielectric
mismatch boundary that caused the coupled signal 112. The coupled
signal 112 can be conveyed along the receive conductive element,
which is monitored by a receiver that can detect and further
manipulate the coupled signal without substantial interference
caused by the signal transmitted on the electrically-separate
transmit conductive element, thereby resulting in improved
performance relative to traditional TDR techniques and enhanced
detection capabilities, particularly when encountering multiple
dielectric mismatch boundaries, close distance measurements, and/or
dielectric mismatch boundaries formed by substances with similar
dielectric constants. Those skilled in the art will recognize that
parasitic capacitance between the transmit and receive conductive
elements and circuit impedance mismatches between transmitter and
receiver circuits (for embodiments in which the transmitter and
receiver circuits are positioned on a single circuit board and not
completely isolated) can cause a parasitic signal 114 to appear on
the receive conductive element, however the small amplitude of this
parasitic signal 114 relative to that of the coupled signal 112
does not materially affect the ability of the receiver to detect
the coupled signal 112, even in close-in situations where the
dielectric mismatch boundary is located close to the source of the
transmitted signal.
[0034] In more detail and with reference to FIG. 2, an entity
interested in monitoring and/or controlling the level, volume,
and/or other characteristics of one or more substances 202, 204,
206 in an open or closed container 208 (e.g., above-ground tank,
below-ground tank, under-water tank, pressurized tank, and/or any
other type of container capable of storing one or more substances)
can, under the control of a processor 210, instruct a transmitter
212 to transmit an electromagnetic signal 214 via one or more
transmit conductive elements 216 in contact with one or more
substances of interest 202, 204, 206. In one illustrative
embodiment, the transmitted signal 214 can exhibit an ultra-wide
band frequency. At least part of the transmitted signal 214 can be
coupled to a receive conductive element 218 in response to the
transmitted signal 214 encountering dielectric mismatch boundaries,
such as the dielectric mismatch boundary 220 associated with
substance A 202 and substance B 204 and the dielectric mismatch
boundary 222 associated with substance B 204 and substance C 206.
The coupled signal 224 returned along the receive conductive
element 218 can be received by a receiver 226 and subsequently
processed by the processor 210 using a time source 228 to perform,
for example, a time comparison analysis between the transmitted
signal 214 and the received signal 224 that can be used to
ascertain one or more characteristics of the substances of interest
202, 204, 206. The processor 210 can also communicate and/or
display the substance characteristics on one or more local and/or
remote digital data processing devices 230 via a data
communications network 230, bus, and/or other type of digital or
analog data path.
[0035] A substance 202-206 can refer generally to any type of
gaseous, liquid, gel, semisolid, and/or solid matter, as well as,
to any solutions, mixtures, compositions and/or combinations
thereof that exhibit discernable dielectric properties. As
discussed above, a dielectric mismatch boundary 220, 222 can refer
generally to a surface or region between substances that exhibit
different dielectric constants. For the purposes of this
disclosure, a dielectric mismatch boundary can also refer to a
boundary between a total or partial vacuum and a substance.
[0036] A processor 210 can refer to the digital logic circuitry
that responds to and processes instructions (not shown) that drive
digital data processing devices 230, multistatic probes 200,
transmitters 212, time sources 228, receivers 226, etc., and can
include, without limitation, a central processing unit, a
micro-controller, an arithmetic logic unit, an application specific
integrated circuit, a task engine, and/or any combinations,
arrangements, or multiples thereof.
[0037] The instructions executed by a processor 210 represent, at a
low level, a sequence of "0's" and "1's" that describe one or more
physical operations of a digital data processing device and/or
multistatic probe system 200. These instructions can be pre-loaded
into a programmable memory (not shown) (e.g., EEPROM) that is
accessible to the processor 210 and/or can be dynamically loaded
into/from one or more volatile (e.g., RAM, cache, etc.) and/or
non-volatile (e.g., FLASH ROM, hard drive, etc.) memory elements
communicatively coupled to the processor 210. The instructions can,
for example, correspond to a) the initialization of hardware within
a digital data processing device and/or a multistatic probe system
200, b) an operating system that enables the hardware elements to
communicate under software control and enables other computer
programs to communicate, and/or c) software application programs or
other computer programs that are designed to perform particular
functions for an entity, such as functions relating to the
operation of the multistatic probe system 200 (e.g., monitor a
level and/or a moisture content of a substance of interest).
[0038] A digital data processing device 230 can be a personal
computer, computer workstation (e.g., Sun, HP), laptop computer,
server computer, mainframe computer, handheld device (e.g.,
personal digital assistant, Pocket PC, cellular telephone, etc.),
information appliance, or any other type of generic or
special-purpose, processor-controlled device capable of receiving,
processing, and/or transmitting digital data. As is known to those
skilled in the art, a digital data processing device can include a
variety of subsystems (e.g., display subsystem, video subsystem,
input/output subsystem, memory subsystem, storage controller
subsystem, network interface subsystem, etc.) and software
processes (e.g., operating system, software application programs,
database, etc.) executing thereon.
[0039] A local user (not shown) can interact with a processor 210
of a multistatic probe system 200 and/or with a digital data
processing device 230 in communication therewith by, for example,
viewing a command line, LED display, graphical, and/or other user
interface and entering commands via an input device, such as a
mouse, keyboard, touch sensitive screen, track ball, keypad, etc.
The user interface can be generated by a graphics subsystem of a
digital data processing device, which renders the interface into an
on or off-screen surface (e.g., in a video memory and/or on a
display screen). Inputs from the user can be received via an
input/output subsystem and routed to a processor 210 via an
internal bus (not shown) (e.g., system bus) for execution under the
control of an operating system.
[0040] Similarly, a remote user (not shown) can interact with a
processor 210 of a multistatic probe system 200 and/or with a
digital data processing device 230 in communication therewith over
a data communications network 232 (e.g., Internet, intranet,
extranet, local area network, metropolitan area network, wide area
network, radio frequency modem, etc.). The inputs from the remote
user can be received and processed in whole or in part by a remote
digital data processing device collocated with the remote user.
Alternatively or in combination, the remote user's inputs can be
transmitted back to and processed by the processor 210 and/or by
the digital data processing device located in proximity thereto via
one or more networks using, for example, thin client technology.
The user interface of the local digital data processing device can
also be reproduced, in whole or in part, at the remote digital data
processing device collocated with the remote user by transmitting
graphics information to the remote device and instructing the
graphics subsystem of the remote device to render and display at
least part of the interface to the remote user.
[0041] Network communications between two or more processors and/or
digital data processing devices typically require a network
subsystem (as embodied in, for example, a network interface card, a
modem, a satellite data modem, etc.) to establish one or more
communication sessions between the processors/devices. A
communication session can refer to a series of interactions between
two or more processors/devices and/or other types of communication
end points that occur during the span of a connection and can
require the use of multiple elements of a data communications
network, a point to point connection, a bus, a wireless transceiver
(e.g., radio frequency modem) and/or any other type of digital
and/or analog data path capable of conveying processor-readable
data.
[0042] A data communications network 232 can comprise a series of
network nodes (e.g., the processor 210, a local digital data
processing device, and/or a remote digital data processing device
230) that can be interconnected by network devices and
communication lines (e.g., public carrier lines, private lines,
satellite lines, etc.) that enable the network nodes to
communicate. The transfer of data (e.g., messages pertaining to
characteristics of substances of interest 202-206) between network
nodes can be facilitated by network devices, such as routers,
switches, multiplexers, bridges, gateways, etc., that can
manipulate and/or route data from a source node to a destination
node regardless of any dissimilarities in the network topology
(e.g., bus, star, token ring), spatial distance (local,
metropolitan, or wide area network), transmission technology (e.g.,
TCP/IP, Systems Network Architecture), data type (e.g., data,
voice, video, or multimedia), nature of connection (e.g., switched,
non-switched, dial-up, dedicated, or virtual), and/or physical link
(e.g., optical fiber, coaxial cable, twisted pair, wireless, etc.)
between the source and destination network nodes.
[0043] As known to those of ordinary skill in the art, a
transmitter 212 (also referred to as transmitter-side circuitry)
can refer to digital and/or analog circuitry that can receive
instructions from and provide status to a processor 210 (via, for
example, a digital-to-analog or analog-to-digital converter), form
one or more electromagnetic signals 214 at a frequency and
amplitude specified by the processor 210, and/or transmit the
electromagnetic signals 214 along one or more transmit conductive
elements 216. In one illustrative embodiment, the transmitter uses
clock signals (which can exhibit, for example, a frequency range of
between about 2 MHz to 8 MHz, such as a square-wave at 3.665 MHz)
received from a pulse rate frequency clock in the time source 228
to perform at least some of its operations.
[0044] As known to those of ordinary skill in the art, a receiver
226 (also referred to as receiver-side circuitry) can refer to
digital and/or analog circuitry that can receive instructions from
and provide status and/or signal information to a processor 210
(via, for example, a digital-to-analog or analog-to-digital
converter), and/or amplify, filter, and digitally sample the return
signal 224 received via the receive conductive element 218.
[0045] As known to those of ordinary skill in the art, a time
source 228 can refer to digital circuitry that can, for example,
provide a pulse rate, variable-delayed frequency clock that
operates on an equivalent time sampling detector that may be
contained within a receiver 226 and which can detect and/or be used
to construct a representation of the received signal 224. In one
illustrative embodiment, the time source 228 can include a delay
controller, such as a voltage integrator op-amp ramp circuit with
capacitor discharge reset to produce a precise linear time ramp for
the delay circuit.
[0046] As known to those of ordinary skill in the art, transmit and
receive conductive elements 216, 218 can refer to structures
capable of conveying electromagnetic energy, such as
coaxial-arranged conductors, dielectric rods, microstrip lines,
coplanar striplines, coplanar waveguides, etc. The transmit and
receive conductive elements 216, 218 can also form a parallel
conductor transmission line structure. Although the multistatic
probe is illustrated with the transmitter 212 and receiver 226
connected to corresponding ends of the transmit and receive
conductive elements 216, 218, those skilled in the art will
recognize that the transmitter 212 and receiver 226 can also be
applied to opposite ends of their respective conductive elements
216, 218 to, for example, measure a velocity of propagation
associated with one or more substances 203, 204, 206.
[0047] Similarly, the transmit and receive conductive elements 216,
218 are illustrated in FIG. 2 as exhibiting substantially the same
characteristics (e.g., length), but those skilled in the art will
recognize that their width, length, orientation, or other
characteristics can vary. In one embodiment, the characteristics of
the transmit and receive conductive elements 216, 218 can be
varied, while their transmission line impedance remains
substantially constant. In another embodiment, their
characteristics can be varied according to a predetermined
arrangement for impedance matching and/or to obtain a desirable
signal response (e.g., a coupled return at a predetermined point on
the probe that can serve as a point of reference). For example, the
receive conductive element 218 can extend to different depths in
the tank 208 containing the substances of interest 202-206 than the
illustrated transmit conductive element 216 (or vice verse), the
transmit and receive conductive elements 216, 218 can be
substantially parallel and equidistant and/or they can exhibit
different orientations, the transmit and receive conductive
elements 216, 218 can be substantially perpendicular to the
dielectric mismatch boundaries 220, 222 or they can exhibit other
angular offsets, the transmit and receive conductive elements 216,
218 can exhibit substantially identical cross-sections (e.g.,
quadrilateral) or they can exhibit different cross-sections, and/or
at least part of the transmit and/or receive conductive elements
216, 218 can be shielded or unshielded, terminated or unterminated,
etc.
[0048] Further and although only a single transmit conductive
element 216 and a single receive conductive element 218 are shown
in FIG. 2 to retain the clarity of the figure, those skilled in the
art will recognize that more than one transmit conductive element
216 and receive conductive element 218 can be provided. In one
embodiment, a plurality (e.g., two or more) of transmit conductive
elements 216 and receive conductive elements 218 can be connected
to a single transmitter 212 and a single receiver 226,
respectively. In another embodiment, a plurality of transmit
conductive elements 216 and receive conductive elements 218 can be
connected to more than one transmitter 212 and more than one
receiver 226, respectively. In one embodiment, a multistatic probe
200 can include a third conductive element (not shown) that
substantially surrounds at least part of the transmit and receive
conductive elements 216, 218 and which can function as an
electromagnetic shield, mechanical wear protection, and/or as a
stiffening/strengthening member for the overall probe 200. In one
embodiment, the third conductive element can be connected to a
ground plane associated with, for example, the receiver 226.
[0049] In one illustrative embodiment and with reference to FIG. 3,
a multistatic probe 200 can include a parallel coplanar strip
transmission line with an insulating spacer 302 that can maintain a
substantially equidistant position between a transmit conductive
element 216 and a receive conductive element 218. The insulating
spacer 302 and transmit and receive conductive elements 216, 218
can be composed of materials that are non-absorptive and that are
resistant to chemicals, temperature, and material build-up on their
surfaces and can thereby maintain an effective dielectric constant.
The material forming the insulating spacer 302 and transmit and
receive conductive elements 216, 218 can also be selected to
exhibit flexible properties (e.g., with comparatively minor shape
memory) that can withstand rolling, folding, kinking, etc., so that
the spacer 302 and conductive elements 216, 218 reform into their
original shapes upon cessation of the forces that caused their
deformation. For example, the insulating spacer 302 can be composed
of polytetrafluoroethylene (manufactured using, for example, a
lamination process), fluorinated ethylenepropylene (manufactured
using, for example, a co-extrusion process), a polyimide, such as
Teflon or Kapton (manufactured using, for example, a co-extrusion
process), and the transmit and/or receive conductive elements 216,
218 can be made of stainless steel (e.g., type 304 or 316).
[0050] In one embodiment, the insulating spacer 302 can be provided
in the form of a laminated tape or film that can substantially
surround at least part of the transmit and receive conductive
elements 216, 218. In one particularly advantageous embodiment, the
transmit and receive conductive elements 216, 218 can be
approximately 0.1 inches wide and 0.004 inches thick and the
insulating spacer 302 substantially surrounding at least part of
the transmit and receive conductive elements 216, 218 can fixedly
space the conductive elements 216, 218 by about 0.305 inches with
an approximate overall width and thickness of the resulting
spacer-conductor assembly 304 of 0.5 inches and 0.025 inches,
respectively. Those skilled in the art will recognize that the
"flat" conductive elements and high quality dielectric exhibited by
the insulating spacer of this particular illustrative embodiment
can result in comparatively low signal loss, reduced levels of
cross-talk between conductive elements, substantially constant
impedance that can reduce the attenuation and dispersion of an
electromagnetic signal, and/or improved sensitivity to a dielectric
mismatch boundary.
[0051] In one embodiment, at least part of an end of the
spacer-conductor assembly 304 can be attached to a weight that may
be useful in maintaining a desired configuration of the assembly
304. For example, the weight can be a corrosion resistant element
that maintains the spacer-conductor assembly 304 in a substantially
vertical position and/or the weight can include a magnet that
anchors the end of the spacer-conductor assembly 304 to a desired
location within a container 208 storing the substances of interest
202-206, such as on a bottom or a wall of the container 208.
[0052] In an illustrative operation and with reference to FIGS. 2
and 4, a processor 210 can instruct a transmitter 212 to form an
electromagnetic signal of interest. In response to the processor
instructions, the transmitter 212 can access a pulse rate frequency
clock associated with a time source 228 to form an electromagnetic
signal 214 exhibiting the attributes (e.g., amplitude and
frequency) specified by the processor 210 and can transmit such
signal 214 on at least one first conductive element 216 (402). In
another embodiment, the processor does not specify attributes of
the electromagnetic signal 214, but rather instructs/triggers other
circuitry to form the electromagnetic signal 214 and/or performs
timing measurements on signals conditioned and/or filtered by other
circuitry.
[0053] When the transmitted signal 214 (e.g., one or more
electromagnetic pulses exhibiting, for example, an ultra-wide band
frequency) encounters one or more regions of the first conductive
element that is/are in contact with, and/or otherwise adjacent to,
one or more dielectric mismatch boundaries 220, 222, a change in
the capacitance of the first conductive element 216 relative to a
second conductive element 218 couples at least part of the
transmitted signal 214 to one or more second conductive elements
218. Under the control of the processor 210, the coupled signal 224
(e.g., one or more electromagnetic pulses exhibiting, for example,
an ultra-wide band frequency) that is based on/excited from the
transmitted signal 214 can be sampled by the receiver 226 using a
controlled time delay of the pulse rate frequency clock of the time
source 228 to form a representation of the coupled signal 224
(404). The coupled signal and/or the representation of the coupled
signal can also be amplified to increase the amplitude of the
signal and/or filtered to remove harmonics and other interfering
signals, such as signals from parasitic coupling between the
transmitter and receiver-side circuitry located on a common printed
circuit board, signals coupled from reflections on the first
conductive element 216, etc. (406).
[0054] The amplified and filtered return signal can be processed by
the processor 210 and/or receiver 226 relative to the transmitted
signal 214 to determine attributes (e.g., a time delay) that can be
used to derive characteristics (e.g., level and/or volume of a
substance) associated with the substances 202-206 that formed the
dielectric mismatch boundary 220, 222 (408). The processor 210 can
subsequently transmit and/or otherwise communicate the attributes
of the return signal and/or the characteristics of the substances
202-206 to an interested entity, such as to a local digital data
processing device, a remote digital data processing device 230, an
LED display, a computer program, and/or to any other type of entity
capable of receiving the attribute and/or characteristic
information (410).
[0055] Those skilled in the art will recognize that, even with the
enhanced performance of the multistatic probe 200 discussed above,
it may be difficult to characterize adjacent substances that
exhibit similar dielectric constants, where such conditions could
result in, for example, a relatively low amplitude in the coupled
signal 224, and/or where the transmit-to-receive time between the
transmitted signal 214 and coupled signal 224 is comparatively
small (which may, for example, experience interference from
parasitic coupling). Accordingly and optionally, the disclosed
technology can include a coupler composed at least in part of a
material exhibiting a comparatively high dielectric constant (e.g.,
ceramics, plastics, etc.), conductive properties (e.g., metals,
metallized materials, ferrites, etc.), and/or other properties that
can be positioned at the dielectric mismatch boundary and that can
create a coupled return signal 224 of substantially consistent
attributes (e.g., amplitude), which is independent of the
dielectric properties of the substances forming the dielectric
mismatch boundary.
[0056] For example and with reference to an exemplary waveform 502,
measured on a receive conductive element of an exemplary
multistatic probe that traverses a dielectric mismatch boundary
formed between substances with similar dielectric constants (e.g.,
air and mineral oil), in FIG. 5, the amplitude of a coupled signal
504 excited on the receive conductive element can be low relative
to that of a corresponding transmit signal conveyed on a transmit
conductive element and, thus, it may be difficult for a receiver to
detect the coupled signal 504 (particularly in close-in situations
where the coupled signal 504 may be partially obscured by a
parasitic signal 506, as previously described). As shown in
waveform 508, a coupler positioned at the same dielectric mismatch
boundary results in a coupled signal 510 that is independent of the
dielectric constants of the substances forming the dielectric
mismatch boundary and can therefore result in a higher amplitude
relative to that of the coupled signal 504 when a coupler is not
used. Accordingly, the likelihood that the receiver will be able to
detect the coupled signal 510 is improved and the enhanced signal
strength of the coupled signal 510 is also less likely to be
obscured by a parasitic signal 512.
[0057] With reference to FIG. 6A, one or more couplers 602 can be
attached to one or more floats 604 (forming, for example, one or
more float-coupler assemblies), which can enable the couplers 602
to slidably move along the transmit and/or receive conductive
elements 216, 218 and be positioned at substantially the same
locations as dielectric mismatch boundaries 220, 222 formed between
substances of interest 202-206. An electromagnetic signal 214
transmitted along the transmit conductive element 216 can induce
and/or excite a coupled electromagnetic signal 224 on the receive
conductive element 218 upon traversing that section of the transmit
conductive element 216 in close proximity to the coupler 602, as
previously discussed. Since the amplitude of the coupled signal 224
is based at least in part on the relatively high dielectric
properties of the coupler 602 located at a dielectric mismatch
boundary 220, 222 and not on the dielectric properties of the
substances of interest 202-206 forming such boundary 220, 222, the
coupled signal 224 can still be considered to be based on a
location of the dielectric mismatch boundary 220, 222. Those
skilled in the art will recognize that a more accurate
determination of the location of the dielectric mismatch boundary
220, 222 can be obtained by also correcting for the velocity of
propagation changes of the signals 214, 224 caused by the
difference in the dielectric constants of the substances
202-206.
[0058] Those skilled in the art will recognize that the properties
(e.g., density, viscosity, etc.) of the substances of interest
202-206 can be used to determine the buoyant properties and other
characteristics (e.g., size, shape, etc.) of a float-coupler
assembly (may also include an optional weight 606 connected to the
float-coupler assembly or transmit/receive conductive elements 216,
218), which can be used to select a particular float-coupler
assembly, such that the coupler 602 can be positioned at
substantially the same location as a dielectric mismatch boundary
220, 222. Although the coupler 602 is shown as having a length
identical to that of the float 604, those skilled in the art will
recognize that the coupler 602 can have a length that is greater or
smaller than that of the float 604. In one embodiment, the coupler
602 can have a length that corresponds to at least one-quarter of a
pulse length of the transmitted signal 214.
[0059] With reference to FIG. 6B, a coupler 602, such as a metallic
sleeve, can exhibit a quadrilateral, circular, oval, U-shaped,
parallel segment, and or other shaped cross-section that can form a
channel capable of accepting the spacer-conductor assembly 304
shown in FIG. 3 and/or other types of spacer-conductor assemblies.
In one illustrative embodiment, the float-coupler assembly can be
formed by stacking stainless steel sheets with quadrilateral
channels defined therein and inserting the stacked sheets into a
closed-cell, Buna-N, Nitrol rubber float, where the quadrilateral
channels are dimensioned to provide sufficient clearance so that
the float-coupler assembly can move freely along the
spacer-conductor assembly 304 (FIG. 3) inserted therethrough. Those
skilled in the art will also recognize that a float 604 with an
internal channel whose walls exhibit a similar conductive path,
such as a metal passage in a metal float, can be used in place of,
or in addition to, the coupler 602.
[0060] As discussed herein, the disclosed technology can be used to
develop a variety of measurement devices that can measure, for
example, levels and other characteristics of substances stored in a
container; the dimensions of an object; a distance between objects;
an angular orientation; a position of a hydraulic cylinder, a
degree of compression of a spring in a weight measuring device, a
displacement of a bellows or diaphragm in a pressure measuring
device; and/or other types of devices that can exhibit changing
states.
[0061] In one illustrative embodiment and with reference to FIG.
7A, the disclosed technology can be used to develop a measurement
device 702 capable of measuring linear distances associated with
one or more objects 704 by, for example, aligning one or more
movable couplers 602 with the positions of interest on the
object(s), transmitting an electromagnetic signal 214 on a first
conductive element 216, receiving one or more coupled
electromagnetic signals 224 on an at least one electrically
separate second conductive element 218 in response to the
transmitted signal 214 traversing those sections of the transmit
conductive element 216 in close proximity to the couplers 602, and
evaluating the attributes of the coupled signals 224 relative to
the transmitted signal 214 to determine a distance 706 between the
positions of interest.
[0062] With reference now also to FIG. 7B, the measurement device
702 can include one or more transmit and receive conductive
elements 216, 218 positioned and/or otherwise integrated within a
plastic or other suitable supporting material 708, which may be at
least partially surrounded by a third conductive element 710 that
may be connected to a ground plane and/or provide strength/rigidity
to the measurement device 702. The supporting material 708 can
include a channel 712 defined therein in close proximity to the
transmit and receive conductive elements 216, 218 and adapted to
receive the slidably movable couplers 602.
[0063] Although the disclosed technology has been described with
reference to specific embodiments, it is not intended that such
details should be regarded as limitations upon the scope of the
invention, except as and to the extent that they are included in
the accompanying claims.
* * * * *