U.S. patent application number 09/796877 was filed with the patent office on 2001-11-15 for handheld sensing apparatus.
This patent application is currently assigned to Cyrano Sciences, Inc.. Invention is credited to Boehr, Christopher K., Nakayama, Robert K., Steinthal, M. Gregory, Sunshine, Steven A..
Application Number | 20010039824 09/796877 |
Document ID | / |
Family ID | 27366646 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010039824 |
Kind Code |
A1 |
Sunshine, Steven A. ; et
al. |
November 15, 2001 |
Handheld sensing apparatus
Abstract
A vapor sensing device that is sufficiently small and
lightweight to be handheld, and also modular so as to allow the
device to be conveniently adapted for use in sensing the presence
and concentration of a wide variety of specified vapors. The device
provides these benefits using a sensor module that incorporates a
sample chamber and a plurality of sensors located on a chip
releasably carried within or adjacent to the sample chamber.
Optionally, the sensor module can be configured to be releasably
plugged into a receptacle formed in the device. Vapors are directed
to pass through the sample chamber, whereupon the sensors provide a
distinct combination of electrical signals in response to each. The
sensors of the sensor module can take the form of chemically
sensitive resistors having resistances that vary according to the
identity and concentration of an adjacent vapor. These chemically
sensitive resistors can each be connected in series with a
reference resistor, between a reference voltage and ground, such
that an analog signal is established for each chemically sensitive
resistor. The resulting analog signals are supplied to an
analog-to-digital converter, to produce corresponding digital
signals. These digital signals are appropriately analyzed for vapor
identification.
Inventors: |
Sunshine, Steven A.;
(Pasadena, CA) ; Steinthal, M. Gregory; (Los
Angeles, CA) ; Boehr, Christopher K.; (San Gabriel,
CA) ; Nakayama, Robert K.; (Los Angeles, CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Cyrano Sciences, Inc.
|
Family ID: |
27366646 |
Appl. No.: |
09/796877 |
Filed: |
February 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09796877 |
Feb 28, 2001 |
|
|
|
09548978 |
Apr 14, 2000 |
|
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60122688 |
Mar 3, 1999 |
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Current U.S.
Class: |
73/29.01 |
Current CPC
Class: |
G01N 33/0031 20130101;
G01N 33/0009 20130101 |
Class at
Publication: |
73/29.01 |
International
Class: |
G01N 007/00 |
Claims
What is claimed is:
1. A handheld sensing apparatus comprising: a housing; a sensor
module mounted in the housing and including at least two sensors
that provide a distinct response to a particular test sample; a
sample chamber defined by one or both of the housing and the sensor
module, the sample chamber incorporating an inlet port and an
outlet port, wherein the at least two sensors are located within or
adjacent to the sample chamber; and an analyzer mounted in the
housing and configured to analyze a particular response from the at
least two sensors, wherein the analyzer identifies or quantifies
analytes within the test sample based on the particular
response.
2. The handheld sensing apparatus of claim 1 further comprising: a
pump mounted in the housing and configured to direct the particular
test sample through the sample chamber, from the inlet port to the
outlet port.
3. The handheld sensing apparatus of claim 1 wherein the particular
response includes a set of signals indicative of changes in
resistances of the at least two sensors due to exposure to the
particular test sample.
4. The handheld sensing apparatus of claim 1 further comprising:
measurement circuitry mounted in the housing and configured to
detect the distinct response from the at least two sensors and to
provide a sensed signal corresponding the distinct response.
5. The handheld sensing apparatus of claim 4 wherein the
measurement circuitry includes a sigma-delta converter.
6. The handheld sensing apparatus of claim 1 wherein the analyzer
receives the distinct response from the at least two sensors and
generates a corresponding signature.
7. The handheld sensing apparatus of claim 6 wherein a plurality of
reference signatures is collected for a plurality of reference
samples and a sample signature is generated for the particular test
sample, and wherein the analyzer is configured to compare the
sample signature against the plurality of reference signatures to
identify the particular test sample.
8. The handheld sensing apparatus of claim 1 further comprising: a
valve mounted in the housing and configured to direct either a
reference sample or an unknown test sample to the sample
chamber.
9. The handheld sensing apparatus of claim 8 wherein the reference
sample is preconditioned.
10. The handheld sensing apparatus of claim 8 wherein the reference
sample is selected from among a plurality of reference samples.
11. The handheld sensing apparatus of claim 1 wherein the sample
chamber is sealed from external environment, except for the inlet
port and the outlet port.
12. The handheld sensing apparatus of claim 1 further comprising a
preconcentrator.
13. The handheld sensing apparatus of claim 1 further comprising:
thermal control circuitry that controls the temperature of the at
least two sensors.
14. The handheld sensing apparatus of claim 1 wherein at least one
of the sensors in the sensor module is a member selected from the
group consisting of a conducting/nonconducting regions sensor, a
SAW sensor, a quartz microbalance sensor, a conductive composite
sensor, a chemiresitor, a metal oxide gas sensor, an organic gas
sensor, a MOSFET, a piezoelectric device, an infrared sensor, a
sintered metal oxide sensor, a Pd-gate MOSFET, a metal FET
structure, a electrochemical cell, a conducting polymer sensor, a
catalytic gas sensor, an organic semiconducting gas sensor, a solid
electrolyte gas sensors, and a piezoelectric quartz crystal
sensor.
15. The handheld sensing apparatus of claim 14 wherein at least one
of the sensors in the sensor module is a conducting/nonconducting
regions sensor.
16. The handheld sensing apparatus of claim 14 wherein at least one
of the sensors in the sensor module is a SAW sensor.
17. The handheld sensing apparatus of claim 1 wherein the sensor
module includes: a plurality of sensor array devices, each sensor
array device including an array of sensors.
18. A handheld sensing apparatus comprising: a housing including a
receptacle; a sensor module removably mounted in the receptacle of
the housing, the sensor module including at least one sensor that
provides a distinct response to a particular test sample; a sample
chamber defined within the sensor module, the sample chamber
incorporating an inlet port and an outlet port, wherein the at
least one sensors is located within or adjacent to the sample
chamber; and an analyzer mounted in the housing and configured to
analyze a particular response from the at least two sensors,
wherein the analyzer identifies or quantifies analytes within the
test sample based on the particular response.
19. The handheld sensing apparatus of claim 18 further comprising:
one or more additional sensor modules, each sensor module
configured to be removably mounted in the receptacle and to
incorporate at least one sensor, wherein each sensor module is
configured to provide a different set of responses to a set of
distinctive samples.
20. The handheld sensing apparatus of claim 19 wherein each
removably mounted sensor module includes an identifier for
identifying the sensor module, and wherein the analyzer is
configured to determine the identifier included in the particular
sensor module received in the receptacle.
21. A sensor module configured for use with a sensing apparatus
disposed within a housing that defines a receptacle, the sensor
module comprising: a casing sized and configured to be received in
the receptacle of the sensing apparatus; a sample chamber; an inlet
port configured to be releasably engageable with a first port
connection of the sensing apparatus when the sensor module is
received in the receptacle, the inlet port receiving a test sample
from the sensing apparatus and directing the test sample to the
sample chamber; an outlet port configured to discharge the test
sample from the sample chamber; at least one sensor located within
or adjacent to the sample chamber and configured to provide a
distinct response when exposed to one or more analytes located
within the sample chamber; and an electrical connector configured
to be releasably engageable with a mating electrical connector of
the sensing apparatus when the sensor module is received in the
receptacle, the electrical connector transmitting the
characteristic signals from the at least one sensor to the sensing
apparatus.
22. The sensor module of claim 21 wherein the outlet port is
configured to be releasably engageable with a second port
connection of the sensing apparatus when the sensor module is
received in the receptacle of the sensing apparatus, the outlet
port discharging the test sample from the sample chamber to the
sensing apparatus.
23. The sensor module of claim 22 wherein the casing incorporates a
rear wall that supports the inlet port, the outlet port, and the
electrical connector.
24. The sensor module of claim 21 further comprising: a substrate
to which the plurality of sensors mounts.
25. The sensor module of claim 21 wherein the at least one sensor
is arranged in a uniform manner within the sample chamber.
26. The sensor module of claim 21 wherein each of the at least one
sensor is implemented with a chemically sensitive resistor having a
resistance that varies in a unique manner when exposed to one or
more specified test samples; and the sensing apparatus includes an
analyzer that detects a set of resistances of the at least one
sensor and identifies the test sample based on the detected set of
resistances.
27. A handheld sensing apparatus for measuring the concentration of
one or more analytes within a sample chamber, comprising: at least
two chemically sensitive resistors, each chemically sensitive
resistor having a resistance that varies according to a
concentration of one or more analytes within the sample chamber;
conditioning circuitry coupled to the at least two chemically
sensitive resistors, the conditioning circuitry generating an
analog signal indicative of the resistance of each of the at least
two chemically sensitive resistors; an analog-to-digital converter
(ADC) coupled to the conditioning circuitry, the ADC responsive to
the analog signal and providing a digital signal; and an analyzer
coupled to the ADC, the analyzer responsive to the digital signal
and determining the identity or concentration of one or more
analytes within the sample chamber.
28. The handheld sensing apparatus of claim 27 wherein the
conditioning circuitry includes a set of voltage divider networks,
one network for each of the at least two chemically sensitive
resistors, each network providing an analog voltage.
29. The handheld sensing apparatus of claim 27 further comprising:
at least one multiplexer coupled to the set of voltage divider
networks, the multiplexer coupling the analog voltage from the set
of voltage divider networks to the ADC.
30. The handheld sensing apparatus of claim 29 further comprising:
at least one amplifier, each amplifier coupled between one
multiplexer and the ADC.
31. A hand-held vapor sensing apparatus, comprising: a hand-held
housing; a sensor module mounted in the housing and incorporating a
plug-in array of vapor sensors, each vapor sensor providing a
different electrical response to one or more distinct vapors;
wherein one or both of the housing and the sensor module define a
sample chamber to which the array of vapor sensors of the sensor
module is exposed, the sample chamber incorporating a vapor inlet
and a vapor outlet; a pump mounted on the housing and configured to
direct a vapor sample through the sample chamber, from the vapor
inlet to the vapor outlet; a monitoring device mounted on the
housing and configured to monitor the electrical responses of the
array of vapor sensors incorporated in the sensor module, and
further configured to produce a corresponding plurality of sensor
signals; and an analyzer mounted on the housing and configured to
analyze the plurality of sensor signals, to identify any vapor
sample directed through the sample chamber by the pump.
32. A plug-in sensor module configured for use with a hand-held
vapor sensing apparatus of a kind including a hand-held housing
that defines a receptacle, the sensor module comprising: a casing
sized and configured to be received in the receptacle of the
hand-held vapor sensing apparatus; a sample chamber; a vapor inlet
configured to be releasably engageable with a first vapor
connection of the hand-held vapor sensing apparatus when the
plug-in sensor module is received in the receptacle of the vapor
sensing apparatus, for receiving a vapor sample from the vapor
sensing apparatus and directing the vapor sample to the sample
chamber; a vapor outlet configured to discharge the vapor sample
from the vapor chamber; and a plurality of vapor sensors located
within or adjacent to the sample chamber and configured to provide
different electrical signals in response to one or more vapors
located within the sample chamber; an electrical connector
configured to be releasably engageable with a mating electrical
connector of the hand-held vapor sensing apparatus when the plug-in
sensor module is received in the receptacle of the vapor sensing
apparatus, to transmit electrical signals from the plurality of
vapor sensors to the vapor sensing apparatus.
33. A vapor sensing apparatus for measuring the concentration of
one or more prescribed vapors within a sample space, comprising: a
chemically sensitive resistor having a resistance that varies
according to the concentration of one or more prescribed vapors
within a sample space; a reference resistor connected in series
with the chemically sensitive resistor, between a reference voltage
source and ground, such that an analog output signal is established
at the node between the reference resistor and the chemically
sensitive resistor; an analog-to-digital converter, responsive to
both the analog output signal and the voltage level of the
reference voltage source, for producing a digital output signal
indicative of the resistance of the chemically sensitive resistor;
and an analyzer, responsive to the digital output signal, for
determining the concentration of one or more prescribed vapors
within the sample space; wherein the vapor sensing apparatus is
configured such that variations in the voltage level of the
reference voltage source will have only an insubstantial effect on
the value of the digital output signal.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/178,443, filed Oct. 23, 1998, which is a
continuation-in-part of U.S. patent application Ser. No.
09/045,237, filed Mar. 20, 1998. This application is also a
continuation-in-part of U.S. patent application Ser. No.
09/141,847, filed Aug. 27, 1998. This application farther claims
the benefit of U.S. Provisional Application Ser. No., entitled
"Electronic-Nose Device," filed Mar. 3, 1999. All of these
applications are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the detection and
identification of analytes using a portable sensing apparatus. More
particularly, the present invention relates to a portable handheld
electronic nose (e-nose) device.
[0003] An electronic nose is an instrument used to detect vapors or
chemical analytes in gases, solutions, and solids. In certain
instances, the electronic nose is used to simulate a mammalian
olfactory system. In general, an electronic nose is a system having
an array of sensors that are used in conjunction with
pattern-recognition algorithms. Using the combination of chemical
sensors, which produce a fingerprint of the vapor or gas, the
recognition algorithms can identify and/or quantify the analytes of
interest. The electronic nose is thus capable of recognizing
unknown chemical analytes, odors, and vapors.
[0004] In practice, an electronic nose is presented with a
substance such as an odor or vapor, and the sensor converts the
input of the substance into a response, such as an electrical
response. The response is then compared to known responses that
have been stored previously. By comparing the unique chemical
signature of an unknown substance to "signatures" of known
substances, the unknown analyte can be determined. A variety of
sensors can be used in electronic noses that respond to various
classes of gases and odors.
[0005] A wide variety of commercial applications are available for
electronic noses including, but not limited to, environmental
toxicology and remediation, biomedicine, such as microorganism
classification or detection, material quality control, food and
agricultural products monitoring, heavy industrial manufacturing,
ambient air monitoring, worker protection, emissions control, and
product quality testing. Many of these applications require a
portable device because they are located in the field or because
they have an inaccessible location for larger laboratory models.
Conventionally, most of the electronic noses have been large
cumbersome laboratory models incapable of being used in the field
and pilot plant applications. If available, a portable or handheld
device would provide the portability required for pilot plant and
field locations. Unfortunately, the portable chemical detectors
that have been developed thus far have many limitations that have
kept them from being widely accepted.
[0006] For instance, U.S. Pat. No. 5,356,594, which issued to Neel
et al., discloses a portable volatile organic monitoring system
designed for use in detecting fugitive emissions. The device
includes a bar code reader for inventorying the emission site. The
device contains a single sensor responsive to ionized gas, however
the device only detects the amount (i.e., concentration) of the
volatile compound. The device is incapable of identifying the
volatile organic compound. Thus, the device is merely a vapor
amount logger and not a portable electronic nose. As such, the user
is required to know the identity of the vapor being quantitated or
this information must be stored elsewhere.
[0007] Another example of a portable device is disclosed in U.S.
Pat. No. 4,818,348 issued to Stetter. Although this portable device
is more sophisticated than the previous example, it still has many
limitations. In this instance, the device is capable of identifying
a gas or vapor, but the applications are quite limited because of
sensor architectural limitations. The sensors making up the array
are permanently fixed, and thus, the number and variety of analytes
and gases that the device is capable of identifying is quite small.
Moreover, because the analyte or vapor being identified interacts
with each sensor of the array in a different amount, the
reproducibility and stability of the device is quite limited. These
limitations effect the device's accuracy in identifying
unknowns.
[0008] In view of the foregoing, there remains a need in the art
for an electronic nose that is portable and, in certain instances,
handheld. Moreover, a device is needed that is useful in a broad
variety of applications and can respond accurately to a broad
variety of gases, analytes, and fluids. A vapor-sensing device is
needed that is very versatile, stable, and meets the needs of a
wide range of industries and users. The present invention fulfills
these and other needs.
SUMMARY OF THE INVENTION
[0009] The invention relates generally to a sensing apparatus (also
referred to as an electronic-nose or e-nose device). The apparatus
is compact and, in certain embodiments, configured to be a handheld
device. The e-nose device can be used to measure or identify one or
more analytes in a medium such as vapor, liquid, gas, solid, and
others. Some embodiments of the e-nose device includes at least two
sensors (i.e., an array of sensors) and, in some other embodiments,
about two to about 200 sensors in an array and preferably about
four to about 50 sensors in the array.
[0010] The e-nose device is versatile and meets the needs of a wide
range of applications in various industries. In certain
embodiments, the device is designed as a slim handheld, portable
device with various functionalities. In another embodiments, the
device is designed as a portable field tool with full
functionality. The e-nose device typically includes an internal
processor for processing samples and reporting data. Optionally,
the device can be coupled to a computer, such as a personal
computer, for access to set-up and advanced features and for
transfer of data files.
[0011] In some embodiments, sections of the e-nose device are
disposed within modules that can be installed, swapped, and
replaced as necessary. For example, the sensor module, sampling
wand or nose, battery pack, filter, electronics, and other
components, can be modularized, as described below. This modular
design increases utility, enhances performance, reduces cost, and
provides additional flexibility and other benefits.
[0012] A specific embodiment of the invention provides a handheld
sensing apparatus that includes a housing, a sensor module, a
sample chamber, and an analyzer. The sensor module and the analyzer
mount in the housing. The sensor module includes at least two
sensors that provide a distinct response to a particular test
sample. The sample chamber is defined by the housing or the sensor
module, or both, and incorporates an inlet port and an outlet port.
The sensors are located within or adjacent to the sample chamber.
The analyzer is configured to analyze a particular response from
the sensors and to identify or quantify, based on the particular
response, analytes within the test sample.
[0013] In a variation of the above embodiment, the housing of the
handheld sensing apparatus includes a receptacle, and the sensor
module is removably mounted in the receptacle of the housing. In
this embodiment, the sensor module can include one or more
sensors.
[0014] Another specific embodiment of the invention provides a
sensor module configured for use with a sensing apparatus. The
sensor module is disposed within a housing that defines a
receptacle. The sensor module includes a casing, a sample chamber,
an inlet port, an outlet port, at least two sensors, and an
electrical connector. The casing is sized and configured to be
received in the receptacle of the sensing apparatus. The inlet port
is configured to be releasably engageable with a port connection of
the sensing apparatus when the sensor module is received in the
receptacle. The inlet port receives a test sample from the sensing
apparatus and directs the test sample to the sample chamber. The
outlet port is configured to discharge the test sample from the
sample chamber. The sensors are located within or adjacent to the
sample chamber and are configured to provide a distinct response
when exposed to one or more analytes located within the sample
chamber. The electrical connector is configured to be releasably
engageable with a mating electrical connector of the sensing
apparatus when the sensor module is received in the receptacle. The
electrical connector transmits the characteristic signals from the
sensors to the sensing apparatus.
[0015] Yet another specific embodiment of the invention provides a
handheld sensing apparatus for measuring the concentration of one
or more analytes within a sample chamber. The sensing apparatus
includes two or more chemically sensitive resistors, conditioning
circuitry, an analog-to-digital converter (ADC), and an analyzer.
Each chemically sensitive resistor has a resistance that varies
according to a concentration of one or more analytes within the
sample chamber. The conditioning circuitry couples to the
chemically sensitive resistors and generates an analog signal
indicative of the resistance of the resistors. The ADC couples to
the conditioning circuitry and provides a digital signal in
response to the analog signal. The analyzer couples to the ADC and
determines, based on the digital signal, the identity or
concentration of the analyte(s) within the sample chamber.
[0016] Yet another embodiment of the invention provides a portable,
handheld vapor sensing apparatus that includes a sensor module
incorporating a plug-in array of vapor sensors that provide
different electrical responses to one or more distinct vapors. The
apparatus includes a handheld housing, and the sensor module
optionally can be removably mounted in a receptacle formed in the
housing. The sensor module defines a sample chamber to which the
array of vapor sensors is exposed. The sample chamber incorporates
a vapor inlet and a vapor outlet, and a pump is mounted within the
housing for directing a vapor sample from the vapor inlet through
the sample chamber to the vapor outlet. A monitoring device also is
mounted within the housing, for monitoring the electrical responses
of the array of vapor sensors and for producing a corresponding
plurality of sensor signals. In addition, an analyzer is mounted
within the housing for analyzing the plurality of sensor signals
and to identify any vapor sample directed through the sample
chamber by the pump.
[0017] In more detailed features of the invention, the handheld
vapor sensing apparatus further includes a controller or processor
configured to control the pump either to direct one of a plurality
of reference vapors or an unknown vapor sample through the sample
chamber. When the controller is controlling the pump to direct one
of the plurality of reference vapors through the sample chamber,
the monitoring device monitors the electrical responses of the
array of vapor sensors to produce a reference signature.
Thereafter, when the controller is controlling the pump to direct
the unknown vapor sample through the sample chamber, the monitoring
device monitors the electrical responses of the array of vapor
sensors to produce a vapor sample signature. The analyzer then
compares the vapor sample signature with a plurality of reference
signatures, to identify the unknown vapor sample.
[0018] In other more detailed features of the invention, the sample
chamber of the handheld vapor sensing apparatus is defined by the
sensor module, alone, and it is sealed from the external
environment except for the vapor inlet and the vapor outlet. In
addition, each sensor module includes a plurality of first
electrical connectors and a plurality of devices of substantially
identical size and shape, the devices together carrying the array
of vapor sensors and each including a second electrical connector
along one edge thereof, for mating engagement with one of the first
electrical connectors.
[0019] In yet further more detailed features of the invention, the
handheld vapor sensing apparatus further includes an electrical
circuit that controls the temperature of the array of vapor
sensors. In addition, when the sensor module is configured to be
removably mounted in the housing receptacle, the module carries an
identifier for identifying the vapor sensors it carries, and the
monitor further is configured to read the identifier carried by the
sensor module received in the receptacle.
[0020] In an embodiment, the sensors are implemented with
chemically sensitive resistors having resistances that vary
according to the concentration of one or more prescribed vapors
within the sample chamber. These chemically sensitive resistors are
each connected in series with a separate reference resistor,
between a reference voltage and ground, such that an analog signal
is established for each chemically sensitive resistor. An
analog-to-digital converter is responsive to these analog signals
and to the reference voltage, to produce digital output signals
indicative of the resistances of the various chemically sensitive
resistors. A multiplexer can be included for sequentially
connecting the various analog output signals to the
analog-to-digital converter. In addition, an analyzer is responsive
to the digital output signals, to determine the presence and/or
concentration of one or more prescribed vapors within the sample
chamber.
[0021] Other features and advantages of the present invention
should become apparent from the following description of the
preferred embodiments, taken in conjunction with the accompanying
drawings, which illustrate, by way of example, the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows a pictorial view of an operator using an e-nose
device of the invention.
[0023] FIGS. 2A and 2B show a top and bottom perspective view,
respectively, of an embodiment of an e-nose device.
[0024] FIG. 3A shows six perspective views of an embodiment of
another e-nose device.
[0025] FIG. 3B shows four different embodiments of noses for the
e-nose device of FIG. 3A.
[0026] FIG. 4 shows a diagram of an embodiment of the subsystems of
the e-nose device.
[0027] FIG. 5 shows an exploded perspective view of some of the
major components of the e-nose device of FIG. 2A.
[0028] FIGS. 6A and 6B show an exploded perspective view of two
embodiments of the mechanical subsystem of the e-nose device.
[0029] FIG. 6C shows an exploded perspective view of an embodiment
of a filter.
[0030] FIGS. 7A-7B show a perspective view and a top sectional
view, respectively, of an embodiment of a sensor module that
includes four sensor devices mounted within two sample
chambers.
[0031] FIG. 7C shows a perspective view of the sensor array
device.
[0032] FIGS. 8A and 8B show a perspective view and a top sectional
view, respectively, of an embodiment of another sensor module that
includes four plug-in sensor devices within a single sample
chamber.
[0033] FIGS. 9A through 9C show a perspective view, a side
sectional view, and a partial top sectional view, respectively, of
an embodiment of a yet another sensor module that includes a single
sensor array device.
[0034] FIG. 10 shows various accessories for the e-nose device
[0035] FIG. 11 shows a perspective view of an e-nose device shown
mounted vertically in an electrical charging station and coupled to
a host computer.
[0036] FIG. 12A shows a diagram of an embodiment of the electrical
circuitry within the e-nose device.
[0037] FIG. 12B shows an embodiment of a voltage divider network
used to measure the resistance of a chemically sensitive
resistor.
[0038] FIG. 12C shows a diagram of another embodiment of the
electrical circuitry within the e-nose device.
[0039] FIGS. 13A through 13G show an embodiment of suitable
flowcharts of the functional steps performed by the e-nose device
in implementing the measurement and analysis procedures.
[0040] FIG. 14 shows a diagram of an embodiment of the menu
selection for the e-nose device.
[0041] FIG. 15 shows a graph of a principal component analysis of
the responses to a series of esters using the handheld apparatus of
the present invention.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0042] FIG. 1 shows a pictorial view-of an operator using an e-nose
device 100 of the invention. In the embodiment shown in FIG. 1,
e-nose device 100 is a portable, handheld instrument for sensing
the presence of one or more specified analytes in a particular
sample. As use herein, a sample is a unit of a vapor, liquid,
solution, gas, solid, or other forms, and mixtures thereof, of a
substance being analyzed. Thus, a sample includes chemical
analytes, odors, vapors, and others. The sample can comprise a
single analyte or a plurality of analytes. In FIG. 1, e-nose device
100 is used for industrial monitoring and detection, i.e., to
identity and quantify noxious gas escaping from an industrial valve
assembly. E-nose device 100 can also be used for many other
applications, as enumerated below.
[0043] FIG. 2A shows a top perspective view of an embodiment of an
e-nose device 100a. E-nose device 100a includes an elongated
housing 110a having a lower end sized to be conveniently grasped
and supported by the hand of an operator. A display 120a and
several push-button control switches 122a through 122c are located
on the housing's topside, for convenient viewing and access by the
operator. Push-button switches 122 are used to control the device
during its various operating modes. Display 120a displays
information about such operating modes and the results of the
device's sensing.
[0044] A tubular sampling wand 130a and an exhaust port 134 are
provided to respectively receive and discharge samples to be
analyzed. The sampling wand is also referred to as a nose or snout.
A plug-in sensor module 150a is shown installed in its socket
located at the base of e-nose device 100a. The operation of sensor
module 150a is described in detail below. An electrical connector
126 located at the lower end of housing 110a allows for
communication with a host computer, and electrical contacts 128
allow for application of external power that could be used to
operate the e-nose device and to recharge the rechargeable battery
within the e-nose device.
[0045] FIG. 2B shows a bottom perspective view of e-nose device
100a. As shown in FIG. 2B, one sampling wand 130a1 is secured in
place and a second sampling wand 130a2 is being stored in an
elongated recess 162 located on the underside of device 100a.
Sampling wand 130a can be stored when not in use and is releasably
secured in place by a pair of spring clips 164a and 164b. Plug-in
sensor module 150a is shown removed from its socket 152.
[0046] FIG. 3A shows six perspective views of an embodiment of
another e-nose device 100b. E-nose device 100b includes a nose
130b, a display 120b, and a set of buttons 124. Similar to e-nose
device 10a, nose 130b in e-nose device 100b is removably coupled to
a housing 110b. A set of connectors 127 allows for interconnection
with external devices and systems.
[0047] FIG. 3B shows four different embodiments of noses 130c
through 130f. As these examples illustrate, the noses can be
specially dimensioned for improved performance in specific
applications.
[0048] FIG. 4 shows a diagram of an embodiment of the subsystems of
e-nose device 100. The upper half of FIG. 4 shows an electrical
subsystem 410 and the lower half shows a (i.e., substantially
mechanical) subsystem 412 that processes test samples. Within
subsystem 412, a test sample is received via a nose 430 and
provided to a manifold 440. Similarly, a reference or background
sample is received via an intake port 432 and provided through a
filter 436 to manifold 440. Filter 436 can be a blank filter, a
carbon filter, or others. Manifold 440 directs the test and clean
samples to a solenoid 444 that selects one of the samples as the
solenoid output. The selected sample is directed through manifold
440 to a sensor module 450. Sensor module 450 includes at least two
sensors that detect analytes in the selected sample. Sensor module
450 generates a signal (or a "signature") indicative of the
detected analytes and provides this signal to electrical subsystem
410. The selected sample is then provided from sensor module 450,
through manifold 440, further through a pump 460, and to an exhaust
port 434. Nose 430, intake port 432, exhaust port 434, and sensor
module 450 in FIG. 4 generally corresponds to nose 130a, intake
port 132, exhaust port 134, and sensor module 150a in FIG. 2A,
respectively.
[0049] FIG. 4 shows an embodiment of subsystem 412. Many other
components and devices (not shown) can also be included in
subsystem 412. Further, it is not necessary for all of the
components and devices shown in FIG. 4 to be present to practice
the present invention. Moreover, the components and devices may be
arranged in different configurations than that shown in FIG. 4. For
example, pump 460 can be coupled to the output of solenoid 444
instead of exhaust port 434.
[0050] As shown by the embodiment in FIG. 4, electrical subsystem
410 includes a PCB assembly 470 that interconnects with a display
472, a battery pack 474, a keypad 476, an analog port 478, an
interface 480, and switches 482a and 482b. Display 474 can be a
liquid crystal display (LCD) and can include backlight controllers
drivers and (optionally) a touchpad. A contrast adjustment
mechanism can be provided to adjust display 472. Electrical
subsystem 410 is described in further detail below.
[0051] FIG. 5 shows an exploded perspective view of some of the
major components of e-nose device 100a. FIG. 5 also depicts an
embodiment of a subsystem 412a. In use, e-nose device 100a is
configured to draw in a test sample (i.e., in a vapor, liquid, or
gas medium) from a location of interest (i.e., the space adjacent
to the valve assembly in FIG. 1) through sampling wand 130a, and to
direct this sample through plug-in sensor module 150a installed in
socket 152. After passing through sensor module 150a, via ports
512a and 512b, the sample is directed outwardly through exhaust
port 134 at the side of the device. At specified times during the
device's various operating modes, a reference sample is drawn into
the device via intake port 132, directed through sensor module
150a, and discharged through exhaust port 134.
[0052] The device's housing 110a can be formed of molded plastic
and includes a lower half 112a and an upper half 112b. Many of the
device's internal components are conveniently and efficiently
mounted on a printed circuit board (PCB) 510 that extends
substantially across the device's interior volume. Display 120a is
mounted at the top end of the PCB, where it is visible through an
aperture 520 formed in the housing's upper half 112a. The
push-button control switches 122a through 122c are mounted below
display 120a, in positions where they can extend through
correspondingly sized openings 522 formed in the housing's upper
half 112a.
[0053] A valve assembly 540 mounted on the underside of PCB 510
receives the test sample drawn into e-nose device 100a via sampling
wand 130a and the reference sample via intake port 132. The test
sample is directed from sampling wand 130a to the valve assembly
via a tube 532, and the clean sample is directed from intake port
132 to the valve assembly via a tube 534. Valve assembly 540 is
configured to select from one of two sources, coming via either
sampling wand 130a or intake port 132. From valve assembly 540, the
sample from the selected source is directed via a tube 536 through
socket 152 to sensor module 150a, which is located on the top side
of the PCB. After analysis by the sensor module, the sample is
directed through a tube 538 to a pump 560 located on the underside
of the PCB. Finally, the sample is discharged from the device by
directing it from pump 560 through a tube 562 to exhaust port 134.
Alternatively, pump 560 could be located in the path between valve
assembly 540 and sensor module 150a. In an embodiment, the
components coming in contact with the sample being processed
(including tubes 532, 534, 536, 538, and 562) are formed of an
inert or non-corrosive material, such as Teflon, stainless steel,
or Teflon-coated metal. Valve assembly 540 in FIG. 5A generally
corresponds to manifold 440 and solenoid 444 in FIG. 4, and pump
560 corresponds to pump 460.
[0054] In certain aspects, the handheld apparatus of the present
invention includes an optional preconcentrator. Advantageously,
with certain analytes, such as high vapor pressure analytes, the
analyte is concentrated on an absorbent. The preconcentrator can be
used to increase the concentration of analytes in the test sample.
Preconcentrators are traps composed of an adsorbent material. In
use, an adsorbent material attracts molecules from the gas sample
that are concentrated on the surface of the adsorbent.
Subsequently, the sample is "desorbed" and analyzed. Suitable
preconcentrator materials include, but are not limited to, a
polymeric adsorbent material, unsilanized glass wool, Teflon or
porus glass fiber, and the like. The adsorbent material is packed
in a tube, such as a steel tube.
[0055] During use, the sample is drawn into the trap that
concentrates the components of interest. In some instances, the
tube is wrapped with a wire through which current can be applied to
heat and thus, desorb the test sample. The sample is thereafter
transferred into the module containing the sensors.
[0056] The preconcentrator can be disposed in various locations
between the sampling wand and the sensor module. In certain
aspects, the preconcentrator can be placed in the nozzle of the
device or, alternatively, in the manifold or other convenient
location upstream of the sensor module. For example, the
preconcentrator can be disposed within valve assembly 540, or
housed in a unit coupled to the valve assembly (not shown in FIG.
5). Optionally, additional valves can be installed in the device
facilitating preconcentration and sensing.
[0057] Suitable commercially available adsorbent materials used in
preconcentrators include, but are not limited to, Tenax TA, Tenax
GR, Carbotrap, Carbopack B and C, Carbotrap C, Carboxen, Carbosieve
SIII, Porapak, Spherocarb, and combinations thereof. Preferred
adsorbent combinations include, but are not limited to, Tenax GR
and Carbopack B; Carbopack B and Carbosieve SIII; and Carbopack C
and Carbopack B and Carbosieve SIII or Carboxen 1000. Those skilled
in the art will know of other suitable absorbents.
[0058] Operation of e-nose device 100 is controlled by a processor
disposed within an electronic unit 570 mounted on the topside of
PCB 510. Electronic unit 570 further includes one or more memory
devices to store program codes, data, and other configuration
information. The electronic unit and control of the e-nose device
is described in further detail below.
[0059] FIG. 6A shows an exploded perspective view of an embodiment
of another subsystem 412b. Subsystem 412b includes a manifold 640a
mounted on a manifold seal plate 642a. Manifold 640a includes
fittings for mounting a valve (or solenoid) 644a, fittings for
mounting a sensor module 650a, and fittings for mounting a pump
660a. The sample is directed between the various sub-assemblies
(e.g., valve 644a, sensor module 650a, and pump 660a) via cavities
located within manifold 640a and tubes (not shown). Manifold 640a
further includes a recessed opening 648a configured to receive a
filter 636a.
[0060] FIG. 6B shows an exploded perspective view of an embodiment
of yet another subsystem 412c. Subsystem 412c includes a manifold
640b mounted on a manifold seal plate 642b via a seal plate gasket
644b. Manifold 640b includes fittings for mounting a valve (or
solenoid) 644b and fittings for mounting a pump 660b. A filter
cartridge 646b mounts on top of manifold 640b and includes a
recessed opening 648b configured to receive a filter element. A
filter cover 636b encloses recessed opening 648b and an O-ring 638b
provides a seal for the filter. The sample is directed between the
various sub-assemblies (e.g., valve 644b and pump 660b) via
cavities located within manifold 640b and tubes (not shown).
[0061] Filter 636, manifold 640, valve 644, sensor module 650, and
pump 660 in FIGS. 6A and 6B correspond to filter 436, manifold 440,
solenoid 444, sensor module 450, and pump 460 in FIG. 4,
respectively.
[0062] FIG. 6C shows an exploded perspective view of an embodiment
of a filter. The filter includes a circular base unit 680 having an
outer wall 682 and an inner wall 686. A set of small-size openings
is disposed within outer wall 682 for drawing in samples into the
filter. A inner circular ring 684 covers inner wall 686 that has
disposed therein another set of small size openings, for drawing
the samples from the filter. A filter material (e.g., charcoal) 688
for filtering the samples is disposed within the space between the
outer and inner walls. O-ring 638b is used to seal the filter.
[0063] FIGS. 7A-7B show a perspective view and a top sectional
view, respectively, of an embodiment of a sensor module 150b that
includes four sensor devices mounted within two sample chambers
710a and 710b. In FIGS. 7A and 7B, sensor module 150b is depicted
as being configured for non-removable securement to the PCB, but
which alternatively could be configured as a plug-in module such as
sensor module 150a. In a specific embodiment, sensor module 150b
incorporates four plug-in sensor array devices 720, each including
eight chemically sensitive sensors 740. Sensor module 150b can
include greater or fewer number of sensor array devices, and each
sensor array device can include greater or fewer number of sensors.
The four sensor array devices 720 are mounted vertically in pairs
on a board 730. A cover 732 having a pair of elongated recesses is
secured overboard 730 so as to define two separate sample chambers
710a and 710b, one for each pair of sensor array devices 720.
Sensor array devices 720 are of similar shape and size, and each
can be received in any one of the four connectors, or receptacles
722, formed in board 730.
[0064] FIG. 7C is a perspective view of one sensor array device
720. In an embodiment, each sensor array device 720 includes an
array of eight chemically sensitive sensors 740, each providing a
particular characteristic response when exposed to a test sample
carrying analytes to be sensed. In an embodiment, the sensors are
implemented using chemically sensitive resistors that provide
particular resistances when exposed to a test sample. A
multi-contact electrical connector 742 is located along the lower
edge of sensor array device 720 and is configured for insertion
into one of four receptacles 722. Suitable sensor arrays of this
kind are disclosed in U.S. Pat. No. 5,575,401, issued in the names
of Nathan S. Lewis et al., entitled "Sensor Arrays for Detecting
Analytes in Fluids," and incorporated herein by reference. Those of
ordinary skill in the art will appreciate that various alternative
chemically sensitive sensors or devices could also be used.
[0065] As shown in FIG. 7B, the test sample is directed through
sensor module 150b from an inlet port 750, through two sample
chambers 710a and 710b, and to an outlet port 760. Sensor array
devices 720 are arranged such that the test sample moves laterally
across the exposed chemically sensitive sensors. Baffles 762 and
764 are located at the respective leading and trailing ends of each
sample chamber, to assist in providing an efficient flow pattern,
as shown in FIG. 7B.
[0066] FIGS. 8A and 8B show a perspective view and a top sectional
view, respectively, of an embodiment of another sensor module 150c
that includes four plug-in sensor devices 820 within a single
cavity or sample chamber 810. Sample chamber 810 is defined, in
part, by a cover 832 that is secured over a board 830. This
configuration can be designed to provide a longer dwell time for
the test sample within the sample chamber, which can be
advantageous in some applications.
[0067] Like the chemically sensitive sensors included on sensor
array devices 720 in FIGS. 7A and 7B, the chemically sensitive
sensors included on sensor array device 820 in FIGS. 8A and 8B can
take the form of the arrays disclosed in U.S. Pat. No. 5,575,401.
Those of ordinary skill in the art will appreciate that various
alternative chemically sensitive sensors or devices could also be
used.
[0068] FIGS. 9A and 9B show a perspective view and a side sectional
view, respectively, of an embodiment of yet another sensor module
150d that includes a single sensor array device 920. In a specific
embodiment, sensor array device 920 includes 32 chemically
sensitive sensors arranged in a two-dimensional grid and is mounted
in a generally horizontal orientation on a socket 922. Of course,
sensor array device 920 can include greater or fewer number of
sensors. A screen 924 (see FIGS. 9B and 9C) overlays sensor array
device 920 and, in an embodiment, includes a separate opening 926
overlaying each chemically sensitive sensor. Screen 924 is attached
to a cover 932, the combination of which defines an upper chamber
934 and a lower chamber 936. As shown in FIG. 9B, the test sample
being analyzed is directed from an inlet port 950 to upper chamber
934, and from there through screen 924 to lower chamber 936 where
it passes across the chemically sensitive sensors. The test sample
then exits through an outlet port 960. Again, it will be
appreciated that various alternative chemically sensitive sensors
and devices could also be used.
[0069] The e-nose device of the invention includes an array of
sensors and, in certain instances, the sensors as described in U.S.
Pat. No. 5,571,401 are used. Various sensors suitable for detection
of analytes include, but are not limited to: surface acoustic wave
(SAW) sensors; quartz microbalance sensors; conductive composites;
chemiresitors; metal oxide gas sensors, such as tin oxide gas
sensors; organic gas sensors; metal oxide field effect transistor
(MOSFET); piezoelectric devices; infrared sensors; sintered metal
oxide sensors; Pd-gate MOSFET; metal FET structures; metal oxide
sensors, such as a Tuguchi gas sensors; phthalocyanine sensors;
electrochemical cells; conducting polymer sensors; catalytic gas
sensors; organic semiconducting gas sensors; solid electrolyte gas
sensors; piezoelectric quartz crystal sensors; and
Langmuir-Blodgett film sensors.
[0070] In a preferred embodiment, the sensors of the present
invention are disclosed in U.S. Pat. No. 5,571,401, incorporated
herein by reference. Briefly, the sensors described therein are
conducting materials and nonconducting materials arranged in a
matrix of conducting and nonconducting regions. The nonconductive
material can be a nonconducting polymer such as polystyrene. The
conductive material can be a conducting polymer, carbon black, an
inorganic conductor and the like. The sensor arrays comprise at
least two sensors, typically about 32 sensors, and in certain
instances 1000 sensors. The array of sensors can be formed on an
integrated circuit using semiconductor technology methods, an
example of which is disclosed in PCT Patent Application Ser. No.
WO99/08105, entitled "Techniques and Systems for Analyte
Detection," published Feb. 19, 1999, and incorporate herein by
reference.
[0071] In certain instances, the handheld device of the present
invention comprises an array of surface acoustic wave (SAW)
sensors, preferably polymer-coated SAW sensors. The SAW device
contains up to six and typically about four sensors in the array.
Optionally, the device includes a preconcentrator with a heater for
desorption of the sample.
[0072] As will be apparent to those of skill in the art, the
sensors making up the array of the present invention can be made up
of various sensor types as set forth above. For instance, the
sensor array can comprise a conducting/nonconducting regions
sensor, a SAW sensor, a metal oxide gas sensor, a conducting
polymer sensor, a Langmuir-Blodgett film sensor, and combinations
thereof.
[0073] FIG. 10 shows various accessories for the e-nose device. A
case 1010 is provided for easy transport of the e-nose device and
its accessories. A power cord 1012 and a car cord 1014 can each
interconnects the e-nose device to a power source (i.e., a wall
socket or car lighter) for recharging a rechargeable battery within
the e-nose device. These cords also allow for operation of the
e-nose device without the battery. A bracket or stand 1016 holds
the e-nose device in the desired position. A (primary or spare)
battery 1018 allows the e-nose device to be used without connection
to a power source. A serial cable 1020 and an analog cable 1022 are
used to interconnect the e-nose device with a personal computer and
other test equipment. A stylus 1024 is provided for use with a
touchscreen. One or more snouts 1030 can also be provided as spares
or for use in a particular set of applications. A sample syringe
1032 can be used for collection of test samples.
[0074] FIG. 11 is a perspective view of e-nose device 100 shown
mounted vertically in an electrical charging station 1108 and
coupled to a host computer 1110. Charging station 1108 recharges
the rechargeable battery of e-nose device 100 via electrical
contacts 128 (see FIGS. 2A and 2B). E-nose device 100 is also
depicted being coupled to host computer 1110 via a data line 1120.
Host computer 1110 can be used to update e-nose device 100 with
various information such as the identity of various target vapors
to which the device is to be exposed, as well as to retrieve
information from the device such as the results of the device's
sample analyses.
[0075] FIG. 12A is a diagram of an embodiment of the electrical
circuitry within e-nose device 100. In an embodiment, the
electrical circuitry measures he resistances of the arrays of
chemically sensitive resistors mounted on the sensor array devices
(see FIGS. 7 through 9) and processes those measurements to
identify and quantify the test sample. The circuitry is mounted, in
part, on the PCB and includes a processor 1210, a volatile memory
(designated as a RAM) 1212, a non-volatile memory (designated as
ROM) 1214, and a clock circuit 1216. In the embodiment in which
plug-in sensor module 150a is used (see FIGS. 2A and 5), the
chemically sensitive resistors are coupled to the electrical
circuitry via mating electrical connectors 552a and 552b (see FIG.
5) that are engaged when sensor module 150a is plugged into e-nose
device 100a.
[0076] The chemically sensitive resistors used to implement the
sensors typically have baseline resistance values of greater than 1
kilo-ohm (K.OMEGA.). These baseline values can vary as much as
.+-.50% over time. For example, a particular chemically sensitive
resistor may have a baseline resistance that varies between 15
K.OMEGA. and 45 K.OMEGA.. This large resistance variability imposes
a challenge on the design of the resistance measurement circuitry.
In addition, the ratio of the change in resistance to the initial
baseline resistance, or .DELTA.R/R, which is indicative of the
concentration of the analytes, can be very small (i.e., on the
order of hundreds of parts per million, or 0.01%). This small
amount of change, likewise, imposes a challenge on the design of
the measurement circuitry. Further, some sensor module embodiments
include multiple (e.g., 32) chemically sensitive resistors, and it
is desirable to measure the resistance values of all resistors with
minimum circuit complexity.
[0077] FIG. 12B shows an embodiment of a voltage divider network
used to measure the resistance of a chemically sensitive resistor
1220. Chemically sensitive resistor (Rch) 1220 is coupled in series
to a reference resistor (Rrei) 1222 to form a voltage divider
network. In an embodiment, a number of voltage divider networks are
formed, one network for each chemically sensitive resistor, with
each network including a chemically sensitive resistor coupled in
series to a corresponding reference resistor. The reference
resistors are selected to have a relatively low temperature
coefficient. In an alternative embodiment, a single reference
resistor is coupled to all chemically sensitive resistors.
[0078] Referring back to FIG. 12A, a power supply 1224 supplies a
predetermined reference voltage (Vref) to the voltage divider
networks such that small changes in the resistance value of each
chemically sensitive resistor cause detectable changes in the
network output voltage. By appropriately selecting the values of
the reference resistors, the electrical current through each
chemically sensitive resistor can be limited, for example, to less
than about 25 micro amperes (.mu.A). This small amount of current
reduces the amount of 1/.function. noise and improves
performance.
[0079] The analog voltages from the resistor divider networks are
provided through a multiplexer (MUX) 1226 to an analog-to-digital
converter (ADC) 1230. MUX 1226 selects, in sequence, the chemically
sensitive resistors on the sensor module. Optionally, a low-noise
instrumentation amplifier 1228 can be used to amplify the voltage
prior to digitization, to improve the ADC's performance and provide
increased resolution.
[0080] In an embodiment, ADC 1230 is a 22-bit (or higher)
delta-sigma ADC having a wide dynamic range. This allows low-noise
amplifier 1228 to be set to a fixed gain (i.e., using a single high
precision resistor). Commercially available low cost delta-sigma
ADCs can reach sampling speeds as fast as about 1 millisecond per
channel.
[0081] In one implementation, the reference voltage provided by
power supply 1224 to the voltage divider networks is also provided
to a reference input of ADC 1230. Internally, ADC 1230 compares the
divider network output voltages to this reference voltage and
generates digitized samples. With this scheme, adverse effects on
the divider network output voltages due to variations in the
reference voltage are substantially reduced.
[0082] The digitized samples from ADC 1230 are provided to
processor 1210 for further processing. Processor 1210 also provides
timing signals to MUX 1226 and ADC 1230. Timing for the data
acquisition can also be provided via a serial link to the ADC and
via select lines of the MUX.
[0083] FIG. 12C is a diagram of another embodiment of the
electrical circuitry within e-nose device 100. In FIG. 12C, four
8-channel multiplexers (MUXes) 1256a through 1256d are provided for
added flexibility. The inputs of MUXes 1256 couple to the voltage
divider networks (not shown) and the outputs of MUXes 1256a through
1256b couple to four amplifiers 1258a through 1258d, respectively.
The select lines for MUXes 1256 are processor controlled. The use
of external MUXes offer a low ON resistance and fast switching
times. The outputs of amplifiers 1258 couple to four inputs of an
ADC 1260.
[0084] Each amplifier 1258 is a differential amplifier having a
reference (i.e., inverting) input that couples to a
digital-to-analog converter (DAC) 1262. The DC offset of the
amplifier is controlled by processor 1250 by measuring the offset
with ADC 1260 and directing DAC 1262 to provide a proper offset
correction voltage. To account for DC drift (i.e., drift in the
baseline resistance of the chemically sensitive resistor) the
offset can be adjusted prior to actual measurement. Further
electrical stability is maintained by placing ADC 1260 on-board and
using differential MUXes.
[0085] In the embodiments in FIGS. 12A and 12C, amplification is
used with the voltage divider networks to achieve detection of PPM
changes in resistance values. It can be shown that a gain of 50
provides detection of single PPM increments. In FIG. 12C,
amplifiers 1258 also match the signal to be sampled with the
full-scale input of ADC 1260. This matching is accomplished by
subtracting out the DC component (using DAC 1262) and amplifying
the AC component. Thus, it is possible to detect single PPM changes
even with a baseline resistance that varies by .+-.50%.
[0086] In FIGS. 12A and 12C, the ADCs used to measure the
resistance values can be implemented using a (i.e., 4-channel)
high-resolution delta-sigma ADC. The delta-sigma ADC's high
resolution coupled with the above-described sensor biasing
scheme(s) deliver high flexibility and precision. Presently
available delta-sigma ADC can provide 20 bits or more of effective
resolution at 10 Hz and 16 bits of resolution at 1000 Hz, with
power consumption as low as 1.4 mW.
[0087] In an embodiment, the delta-sigma ADC includes differential
inputs, programmable amplifiers, on-chip calibration, and serial
peripheral interface (SPI) compatibility. In an embodiment, the ADC
internal differential MUXes are configured: (1) with respect to
ground for increased effective resolution of the measurement, and
(2) configured with respect to the reference voltage for high
precision measurement, enhanced electronic stability, and to
provide a ratiometric measuring mechanism. A status signal from the
ADC indicates when the internal digital filter has settled, thus
providing an indication to select the next analog channel for
digitization.
[0088] In FIGS. 12A and 12C, processors 1210 and 1260 can be
implemented as an application specific integrated circuit (ASIC), a
digital signal processor (DSP), a controller, a microprocessor, or
other circuits designed to perform the functions described
herein.
[0089] One or more memory devices are provided to store program
codes, data, and other configuration information, and are mounted
adjacent to the processor. Suitable memory devices include a
random-access memory (RAM), a dynamic RAM (DRAM), a FLASH memory, a
read only memory (ROM), a programmable read only memory (PROM), an
electrically programmable ROM (EPROM), an electrically erasable and
programmable PROM (EEPROM), and other memory technologies. The size
of the memories is application dependent, and can be readily
expanded as needed.
[0090] In an embodiment, the processor executes program codes that
coordinate various operations of the e-nose device. The program
codes include interaction software that assists the user in
selecting the operating modes and methods and to initiate the
tests. After the e-nose device performs a test or operation, the
user is optionally presented with concise results. In the
embodiment in which the device includes a processor and a built-in
algorithm, complex functions and capabilities can be provided by
the device. In other embodiments in which simplified electronics is
provided, complex functions and capabilities of the e-nose device
are optionally set up and driven from a host computer using PC
based software.
[0091] The processors can also be used to provide temperature
control for each individual sensor array device in the sensor
module. In an implementation, each sensor array device can include
a back-side heater. Further, the processor can control the
temperature of the sample chambers (e.g., chambers 710a and 710b in
FIG. 7A) either by heating or cooling using a suitable
thermoelectric device (not shown).
[0092] After the processor has collected data representing a set of
variable resistance measurements for a particular unknown test
sample, it proceeds to correlate that data with data representing a
set of previously collected standards stored in memory (i.e.,
either RAM 1212 or ROM 1214). This comparison facilitates
identification of analytes present in the sample chamber and
determination of the quantity or concentration of such analytes, as
well as detection of temporal changes in such identities and
quantities. Various analyses suitable for identifying analytes and
quantifying concentration include principal component analysis,
Fischer linear analysis, neural networks, genetic algorithms, fuzzy
logic, pattern recognition, and other algorithms. After analysis is
completed, the resulting information is displayed on display 120 or
transmitted to a host computer via interface 1232, or both.
[0093] The identification of analytes and the determination of
sample concentration can be performed by an "analyzer." As used
herein, the analyzer can be a processor (such as processors 1210
and 1260 described above), a DSP processor, a specially designed
ASIC, or other circuits designed to performed the analysis
functions described herein. The analyzer can also be a
general-purpose processor executing program codes written to
perform the required analysis functions.
[0094] As noted above, to facilitate identification of specified
analytes, the variable resistance data from the sensors for a
particular unknown test sample can be correlated with a set of
previously collected standards stored in memory. These standards
can be collected using one of at least two suitable techniques, as
described below.
[0095] In one technique, a known reference sample is provided to
the sample chamber(s). The known sample can be supplied from a
small reference cartridge (i.e., located within the e-nose device).
The supplies of this reference sample to the sample chambers can be
controlled by a compact solenoid valve under the control of the
processor. An advantage of using a known reference sample is the
ability to control the identity of the reference sample. The
cartridge can be replaced periodically.
[0096] In another technique, the unknown test sample supplied to
the sample chambers can be selectively "scrubbed" by diverting it
through a cleansing agent (e.g., charcoal). Again, the diversion of
the test sample through the cleansing agent can be controlled by
the processor via a compact solenoid valve. An advantage of this
variation is that a cartridge is not needed. The cleansing agent
can be cleaned periodically, although it may be difficult to ensure
that the reference sample is free of all contaminants.
[0097] The processors in FIGS. 12A and 12C direct data acquisition,
perform digital signal processing, and provide control over serial
peripheral devices (via SPI), I/O devices, serial communications
(via SCI), and other peripheral devices. Serial peripheral devices
that can be controlled by the processors include the ADC and DAC, a
32K external EPROM (with the capability to expand to 64K), a 32K
RAM with integrated real time clock and battery back up, a
2.times.8-character dot matrix display, and others. I/Os that can
be controlled include five separate temperature probes (four are
amplified through amplifiers and are used for four independent
heater control loops utilizing transistors), a humidity probe, two
push buttons, a green LED, and others. Serial communications to
external devices is provided by the on-board low power RS-232
serial driver.
[0098] The processors further control the peripheral devices such
as the display, the valve assembly, and the pump. The processors
also monitor the input devices (e.g., push button switches 122 in
FIG. 2A) and further provides digital communication to a host
computer via an interface (e.g., the RS-232 driver) located in the
device's housing (e.g., electrical connector 126 in FIG. 2A).
[0099] In the embodiment in FIG. 12C, data acquisition includes
communication and/or control over the (i.e., 20 bit) delta-sigma
ADC, the 4-channel (i.e., 12-bit) DAC 1262, and the four discrete
8-channel high-speed analog MUXes 1256.
[0100] The on-board memory (i.e., external RAM) is provided for
data logging purposes. In an embodiment, the memory is organized in
blocks of 32K.times.8 bits. In an embodiment, each sample from the
ADC is 24 bits and occupies three bytes of memory. Thus, each
32K-byte memory block provides storage for 10,666 samples. If all
32 channels are used for data logging purposes, the memory block
provides storage for 333 data points/channel. An internal power
supply preserves the data stored in the memory and is designed with
a lifetime of over five years. The ADC sampling rate is
programmable and the data can be downloaded over the digital RS-232
interface to the host computer.
[0101] Communication between the on-board processor and the host
computer is available to configure the device and to download data,
in real time or at a later time via the RS-232 interface. A
transfer rate of 9600 bits/second can transmit approximately 400
data points/second, and higher transfer rates can be used.
[0102] FIGS. 13A through 13G depict an embodiment of suitable
flowcharts of the functional steps performed by the e-nose device
in implementing the measurement and analysis procedures outlined
generally above. These flowcharts show how the e-nose device is
initialized and then controlled through its various operating
modes. In an embodiment, these operating modes include: 1) a Target
mode, in which the device is calibrated by exposing it to samples
of known identity, 2) an Identify mode, in which the device is
exposed to a samples of unknown identity, and 3) a Purge mode, in
which the device is purged of resident samples.
[0103] FIG. 13A shows a flow diagram of an embodiment of the main
program menu of the e-nose device. Initially, the e-nose device's
various electronic elements (i.e., the display and various internal
data registers) are initialized or reset, at a step 1312. A
function background subroutine is then executed, at a step 1314.
This subroutine is further described in FIG. 13B.
[0104] After executing the function background subroutine, the
program proceeds to a step 1316 in which the processor determines
whether or not push-button switch B1 (e.g., switch 122a in FIG. 2A)
is being pressed. If it is, the program proceeds to a step 1318 in
which the device's operating mode increments to the next succeeding
mode (i.e., from the Target mode to the Identify mode). Thereafter,
the program returns to step 1314 and re-executes the function
background subroutine. The incrementing of the device's operating
mode continues until it is determined in step 1316 that switch B1
is no longer being pressed.
[0105] If it is determined at step 1316 that push button B1 is not
(or no longer) being pressed, the program proceeds to a step 1320
in which it is determined whether or not push-button switch B2
(e.g., switch 122b in FIG. 2A) is being pressed. If switch B2 is
not being pressed, the program returns via an idle loop 1322 to
step 1314 and re-executes the function background subroutine.
Otherwise, if it is determined at step 1320 that push-button switch
B2 is being pressed, the program proceeds to implement the selected
operating mode. This is accomplished by the flowchart depicted in
FIG. 13C. FIG. 13B shows a flow diagram of an embodiment of the
function background subroutine (step 1314). At a step 1330, signals
indicative of the measurements and parameters selected by the user
(i.e., the temperature and humidity within the sample chambers of
the sensor module) are read from the ADCs configured to detect the
input devices (also referred to as the internal ADCs). The status
of the push-button switches (e.g., switches 122a through 122c FIG.
2A) are determined, at a step 1332, based on the signals from the
internal ADCs. The signals controlling the heaters located on
various sensor array devices of the sensor module are then updated,
at a step 1334. Signals indicative of the measurements of the
divider networks, formed by the chemically sensitive resistors and
their corresponding reference resistors, are read from the
instrumentation ADCs (also referred to as the external ADCs), at a
step 1336. Finally, at a step 1338, the processor processes any
commands received from the host computer via the serial data line.
Such commands can include, for example, programming information
about the identity of various reference samples to be supplied to
the e-nose device during the target operating mode. The function
background subroutine then terminates.
[0106] FIG. 13C shows a flow diagram of an embodiment of a
subroutine for determining which one of the operating modes to
implement. At a step 1340, a determination is made whether or not
the-selected operating mode is the Target mode. If it is not, a
determination is made whether or not the selected operating mode is
the Identify mode, at a step 1342. Typically, the Identify mode is
selected only after the target mode subroutine has been implemented
for all of the designated target samples. If the selected operating
mode is the Identify mode, the program executes the identify mode
subroutine (depicted in FIG. 13E), at a step 1344.
[0107] Otherwise, if the selected operating mode is not the
Identify mode, a determination is made whether or not the selected
operating mode is the Purge mode, at a step 1346. If it is, the
program executes the purge mode subroutine (depicted in FIG. 13F),
at a step 1348. Otherwise, the program executes the purge target
mode subroutine (depicted in FIG. 13G), at a step 1350. The purge
target mode is the default mode.
[0108] Back at step 1340, if it is determined that the selected
operating mode is the Target mode, the program proceeds to a step
1352 in which the function background subroutine is executed. This
provides updated values for the internal and external ADCs, as
described above. Thereafter, at a step 1354, it is determined
whether or not push-button switches B1 and B2 are being pressed
concurrently. If they are, the program does not implement the
Target mode and instead returns to the idle loop (step 1322 in FIG.
13A).
[0109] Otherwise, if it is determined at step 1354 that both
push-button switches B1 and B2 are not being pressed concurrently,
the program proceeds to a step 1356 in which it is determined
whether or not switch B1 has been pressed. If it has been, the
program proceeds to a step 1358 in which the particular target
number is incremented. In an embodiment, the e-nose device is
configured to measure multiple (e.g., eight) different target
samples, and step 1358 enables the operator to select the
particular target sample that is to be drawn into the device for
measurement. The identity of these target samples previously has
been loaded into the device from the host computer. Thereafter, the
program returns to the step 1352 to execute the function background
subroutine. Each time it is determined that switch B1 has been
pressed, the program cycles through this loop, incrementing through
the preloaded complement of target samples.
[0110] If it is determined at step 1356 that switch B1 has not been
pressed, the program proceeds to a step 1360 in which it is
determined whether or not switch B2 has been pressed. If it has
not, the program returns to step 1352 to execute the function
background subroutine. Otherwise, if it is determined in step 1360
that switch B2 has just been pressed, the program proceeds to
implement the target mode subroutine (depicted in FIG. 13D), at a
step 1362.
[0111] FIG. 13D shows a flow diagram of an embodiment of the target
mode subroutine. At a step 1370, the most recently updated set of
measurements from the external ADC is retrieved. These measurements
represent the baseline resistance values of the 32 chemically
sensitive resistors of the sensor module. Next, the pump is
conditioned to draw the designated target sample into the sensor
module's sample chamber(s), at a step 1372. A new set of
measurements is then retrieved from the external ADC, at a step
1374. This new set of measurements indicates the resistance values
of the 32 chemically sensitive resistors as they respond to the
target sample that has been drawn in the sample chamber(s).
[0112] At a step 1376, the 32 resistance measurements (i.e., the
"response vector") for this particular target vapor are normalized.
In an embodiment, this normalization set the sum of all 32
measurements equal to a value of 1.times.10.sup.6. The normalized
response vector for His target sample then is stored in memory, at
a step 1378. Finally, at a step 1380, the pump and valve assembly
are configured to draw clean air into the sample chamber(s). The
target mode subroutine then terminates, and the program returns to
the idle loop (step 1322 in FIG. 13A).
[0113] FIG. 13E shows a flow diagram of an embodiment of the
identify mode subroutine. Steps 1390, 1392, 1394, and 1396 in FIG.
13E are similar to steps 1370, 1372, 1374, and 1376 in FIG. 13D,
respectively. At a step 1398, the normalized response vector for
the unknown sample calculated in step 1396 is compared with the
normalize response vectors for the various target samples, as
determined by earlier passes through the target mode subroutine
(FIG. 13D) and stored in memory. Specifically, differences between
the respective normalized response vectors are calculated at step
1398, and the smallest difference vector is determined (i.e., using
a least mean square analysis), at a step 13100. Also at step 13100,
the result of that determination is displayed on a display.
Finally, at a step 13102, the pump and valve assembly are
conditioned to draw clean air to the sample chamber(s). The
identify mode subroutine then terminates, and the program returns
to the idle loop (step 1322 in FIG. 13A).
[0114] FIG. 13F shows a flow diagram of an embodiment of the purge
mode subroutine. At a step 13120, the pump and valve assembly are
conditioned to draw clean air into the sample chamber(s) via the
intake port. The program then returns to the idle loop (step 1322
of FIG. 13A).
[0115] FIG. 13G shows a flow diagram of an embodiment of the purge
target mode subroutine. At a step 13130, all of the target sample
information stored in memory is erased. The program then returns to
the idle loop (step 1322 in FIG. 13A).
[0116] FIG. 14 shows a diagram of an embodiment of the menu
selection for the e-nose device. In FIG. 14, a main menu 1408
displays the measurement modes available for the particular e-nose
device. The available modes can be dependent, for example, on the
particular modules installed in the e-nose device. In an
embodiment, the following modes are available in the main menu:
Identify, Quantify (Qu), Process Control (PC), Data Logging (DL),
Train, and Diagnoses. Upon making a mode selection in menu screen
1408, a menu screen 1410 appears that queries the user to select a
particular method from among a set of available methods.
[0117] By selecting the ID Method option, a menu screen 1412
appears that queries the user to press "sniff" to begin
identification or "cancel" to return to the main menu. Upon
selecting the sniff option, the e-nose device begins the
identification process, as shown in a menu screen 1414, and
provides the results upon completion of the process, as shown in a
menu screen 1416. The user is provided with an option to save the
results.
[0118] By selecting the Qu Method option, a menu screen 1420
appears that queries the user to select a target. If the identity
of the target is unknown, a menu screen 1422 provides the user with
the option of performing a sniff to identify the unknown target.
Upon selecting the sniff option, the e-nose device begins the
identification process, as shown in a menu screen 1424, and
provides the identity upon completion of the process, as shown in a
menu screen 1426. Once the sample is identified or if the identity
is known initially, the target can be quantified in menu screens
1426 and 1428. The e-nose device begins the quantification process,
as shown in a menu screen 1430, and provides the results upon
completion of the process, as shown in a menu screen 1432.
[0119] By selecting the PC Method option, a menu screen 1440
appears that queries the user to press "sniff" to begin the process
control or "cancel" to return to the main menu. Upon selecting the
sniff option, the e-nose device begins the process control, as
shown in a menu screen 1442, and provides the status report, as
shown in a menu screen 1444.
[0120] By selecting the DL Method option, a menu screen 1450
appears that queries the user to press "sniff" to begin the data
logging or "cancel" to return to the main menu. Upon selecting the
sniff option, the e-nose device begins the data logging process, as
shown in a menu screen 1452, and provides the status report, as
shown in a menu screen 1454.
[0121] By selecting the Train option, a menu screen 1460 appears
that queries the user to select one of a number of training
methods. The user selects a particular method and a menu screen
1462 appears that queries the user to select one of a number of
targets. The user selects a particular target and a menu screen
1464 appears that queries the user to press "sniff" to begin the
training. Upon selecting the sniff option, the e-nose device begins
the training process using the method and target selected by the
user, as shown in a menu screen 1466.
[0122] By selecting the Diagnostics option, a menu screen 1470
appears that queries the user to select a diagnostic to run.
Possible diagnostics include, for example, RS-232 port, USB port,
sensor range test, memory, processor, and program check sum. The
user selects a particular diagnostic and the e-nose device begins
the selected diagnostic test, as shown in a menu screen 1472, and
provides the diagnostic results, as shown in a menu screen
1474.
[0123] Modular Design
[0124] In certain aspects of the invention, the e-nose device is
designed using modular sections. For example, the nose, filter,
manifold, sensor module, power pack, processor, memory, and others
can optionally be disposed within a module that can be installed or
swapped, as necessary. The modular design provides many advantages,
some of which are related to the following characteristics:
exchangeable, removable, replaceable, upgradable, and
non-static.
[0125] With a modular design, the e-nose device can be designed for
use in wide variety of applications in various industries. For
example, multiple sensor modules, filters, and so on, can be added
as the list of samples to be measured expands.
[0126] In certain embodiments, the modular design can also provide
improved performance. The various modules (i.e., nose, filter,
manifold, sensor module, and so on) can be designed to provide
accurate measurement of a particular set of test samples. Different
modules can be used to measure different samples. Thus, performance
is not sacrificed by the use of a small portable e-nose device. For
example, to sense high molecular weight analytes, a certain
particular nose chip is plugged in. Then, to analyze lower
molecular weight analytes, another nose chip may be plugged in.
[0127] The modular design can also result in a cost effective
e-nose design. Since some of the components can be easily replace,
it is no longer necessary to dispose the entire e-nose device if a
particular component wears out. Only the failed components are
replaced.
[0128] In certain embodiments, the modular design can also provide
an upgradable design. For example, the processor and memory module
(individually or in combination) can be disposed within an
electronic unit that can be upgraded with new technologies, or as
required by on the particular application. Additional memory can be
provided to store more data, by simply swapping out memory modules.
Also, the analysis algorithms can be included in a program module
that inserts into the e-nose device. The program modules can then
be swapped as desired.
[0129] The modular design can also provide for disposable modules.
This may be advantageous, for example, when analyzing toxic
samples.
[0130] Nose
[0131] In the embodiments described above, the e-nose device
includes an external sampling wand (or nose or snout). The nose can
be attached to the device using a mechanical interconnect, such as
a simple 1/4-turn type, a threaded screw, a snap-on mechanical
arrangement, and other interconnect mechanisms. Many materials can
be used to fabricate the nose component, such as injection moldable
materials.
[0132] In certain embodiments, the nose is interchangeable and uses
a standard luer interconnection. The nose can be, for example,
about 1 inch to about 50 inches in length and, preferably, the nose
is about 6 inches to about 20 inches in length. The nose can
optionally be ridged, or be a long flexi-hose or a flexible
snorkel. In some embodiments, the nose has a luer needle on the
smelling end. Optionally, the nose can withstand an internalized
pressure and is joined with a pressured valve.
[0133] As shown in FIG. 3B, the nose can be dimensioned in various
sizes and shapes. For example, nose 130d includes a wide opening
that may be advantageous, for example, when sampling a gas. In
contrast, nose 130f includes a pointed tip that is more suited for
sampling at a specific site.
[0134] In some alternative embodiments, intake ports (such as
intake port 132) can be used to receive test samples. The intake
ports can substitute for, or supplement the external nose.
[0135] Sensor Modules
[0136] In certain aspects, the chemically sensitive sensors in the
sensor module can be tailored to be particularly sensitive to
particular classes of vapors. For example, the array for one such
module can incorporate vapor sensors suitable for differentiating
polar analytes such as water, alcohol, and ketones. Examples of
polar polymers suitable for use as such vapor sensors include poly
(4-vinyl phenol) and poly (4-vinyl pyrrolidone).
[0137] The sensor module can optionally be identified by means of
an identification resistor (not shown) having a selected
resistance. Thus, prior to processing the variable resistance
measurements collected for the chemically sensitive resistors of
each such sensor module, the processor measures the resistance of
the identification resistor. In this manner, the nature of the
module's chemically sensitive resistors can be initially
ascertained.
[0138] A mechanism for detection of analytes is disclosed in the
aforementioned PCT Patent Application Ser. No. WO99/08105.
[0139] Display
[0140] In some embodiments, the display is a liquid-crystal display
(LCD). In other embodiments, the display is a graphical LCD that
allows the device to display text and graphics. This type of
display provides a quality product interaction experience. Examples
of LCD modules include those manufactured by Epson Corporation,
such as the EPSON EG7502 (TCM AO822) having a screen size of 57.56
mm by 35.99 mm, a 320.times.200 resolution with 0.8 dot pitch, and
transflective and LED edge back light. Various other LCD modules
are also suitable. Preferred LCD modules offer one or more of the
following features: (1) higher resolution to allow for a smaller
but comfortable display viewing areas (320.times.200 and fine dot
pitch), (2) low power consumption (e.g., 3 mW to 9 mW), (3)
multi-line scanning-(active addressing) technology, (4) integrated
"touch" panel, (5) integrated power supply and controller chips,
(6) LED backlighting--for smaller module, (6) displays used with
video, and other features.
[0141] Input Devices
[0142] In certain embodiments, the e-nose device optionally
includes input devices, such as push buttons, a keypad, a keyboard,
a touchscreen, switches, other input mechanisms, or a combination
of the above. The keypad can be fabricated from various materials.
In certain embodiments, the keypad is molded from silicone rubber,
which advantageously provides tactile feedback for gloved hands.
Moreover, navigational controls can optionally be incorporated into
the keypad and buttons. For example, a "sniff" button can be
optionally positioned into the keypad.
[0143] The keypad can optionally be a membrane type keypad. In this
implementation, the keypad is formed from laminated sheets of
acrylic, Mylar, PC, or other suitable materials. Snap domes can be
used to achieve greater tactile feedback for the user. Product
graphics can be incorporated into the keypad. Advantageously, the
keypad has flexibility with graphics, is easy to clean, and has
protection from spillage. In addition, the keypad is configured
with low stroke distances. In certain other instances, a
micro-switch, such as for a "sniff" button, is used to further
accentuate the tactile "click" feedback and generate a low-level
audible signal.
[0144] In certain embodiments, the e-nose device optionally
includes a pointer. Advantageously, the pointer provides greater
application flexibility and ease of use in the field. In certain
aspects, the pointer can be used for bar code reading and easy
inventory control. Further, the device optionally includes a pad.
The pad allows for application flexibility, such as in field,
training, or lab use.
[0145] The e-nose device optionally includes other input devices,
such as a touch screen. Suitable touch screens include the analog
resistive type. Other touch screens include those similar to the
ones in PDA, GPS, and other products. Yet other touch screens
include electromagnetic resonance types optionally having a
dedicated stylus, such as a battery-less stylus. In addition, touch
screens can include, but are not limited to, electrostatic, GSAW,
and analog resistive and capacitive types. The analog resistive
touch screen is preferred since high and low resolutions can
readily be achieved.
[0146] In certain embodiments, the e-nose device notifies the user
by providing general and specific information about the device's
current mode. Operators of the device can see what options are
available. Guidelines and instructions are available to assist the
users interact with the product. In certain instances, the
descriptions and instructions are brief and specific. Graphics and
icons assist users through the product interaction. Users are
provided with a mechanism to stop the device when necessary, and to
return to previous screens where appropriate. These various
features collaborate to provide device interactions that are quick,
simple, and reliable.
[0147] In other embodiments, the e-nose device provides the users
with information regarding the status of the device. Examples
include, but are not limited to, initiating an action, performing
an operation, waiting for input, and so on. Moreover, other device
input and output parameters, such as hardware controls, include,
but are not limited to: Scroll Up--keypad; (2) Scroll Down--keypad;
(3) Select--keypad; (4) Cancel--keypad; (5) Sniff--keypad; (6)
Power-on/Backlight on/off; (7) Digital Input--connector; (8) Analog
Output--connector; (9) Serial out (RS232)--RJ11; (10) USB--Standard
A; (11) Display contrast--(thumbwheel, analog pot); (12) System
reset--pin hole; (13) Battery recharge--jack; (14) pneumatics
ports; (15) nose inhale port (sample sniff port); (16) exhale
(exhaust); and (17) reference intake.
[0148] Power Pack
[0149] The e-nose device optionally includes a power pack, such as
a battery, for providing electrical power. In certain embodiments,
the device operates from power supply voltages of approximately 3.3
volts and approximately 5.0 volts DC. In a specific embodiment, the
device consumes approximately 3.2 watts or less, with a typical
average power consumption of approximately 1.8 watts. In an
embodiment, the device is capable of operation from about 1 hour to
about 20 hours without requiring a recharge of the power pack.
[0150] The power pack can be fabricated using nickel cadmium
(NiCd), nickel-metal hydride (NiMH), lithium ion (Li-ion), sealed
lead-acid (SLA), or other battery technologies. Preferably, the
battery pack has low weight and a high power density to keep the
volume of the battery small. Lithium-ion cells have a relatively
high internal resistance and wider range of voltages during a
discharge compared to other battery chemistries. A voltage
regulator can be used to provide proper voltages for the circuitry
within the e-nose device. For efficiency, a switching voltage
regulator can be used in place of linear type regulators. The
voltage regulator can also be used to provide multiple output
voltages for different circuitry within the e-nose device. In
certain instances, output voltages required from the power supply
include values above and below the battery voltage. In these
instances, a SEPIC topology for the switching regulator can
optionally be used. Conversion efficiency of such switching
regulators is approximately 85%. To provide approximately 18
watt-hours of energy to the load using such switching regulator,
the energy requirement from the lithium-ion battery pack is
approximately 21 watt-hours.
[0151] In a specific embodiment, a lithium-ion (Li-ion) battery
pack of approximately 100 cubic centimeters (cc) in volume and
about 250 grams in weight can optionally be used for the e-nose
device. In another specific embodiment, a nickel-metal hydride
(NiMH) battery pack can be used that weighs about 370 grams and has
a volume of about 150 cc. Other batteries capable of providing an
equivalent amount of energy include, but are not limited to, a
nickel-cadmium (NiCd) battery pack of approximately 560 grams and
210 cc and a sealed lead-acid (SLA) battery pack of approximately
750 grams and 350 cc.
[0152] In general, charging times increase and the available
battery capacity reduces for low (e.g., 0 to 10.degree. C.) and
high (e.g., 40 to 50.degree. C.) temperatures. For accurate "gas
gauging" under such conditions, the Smart Battery System (SBS) can
also be employed. The SBS is part of a commercially available
System Management Bus (SMB) system. The SBS allows battery packs to
communicate to smart chargers and other system intelligence using a
physical protocol similar to the I.sup.2C bus protocol from Philips
Corporation. The software protocol on the SMB allows for direct
communication of parameters such as the state of charge, battery
pack voltage, battery temperature, number of discharge cycles, and
so on. Several vendors of integrated circuits now offer single chip
implementations of the SMB interface. Alternatively, a custom
programmed microcontroller, such as a PIC chip Microchip Technology
Inc., can be used for this purpose.
[0153] In some embodiments, the device includes a power pack that
is optionally chargeable. In some other embodiments, the device
optionally includes batteries such as, for example, four AA cells.
The cell chemistries can vary. The device optionally accommodates
alkaline interchangeability.
[0154] The device optionally has a fitting for a secondary
rechargeable pack that can be the same, or smaller, size as the
power devices described above.
[0155] Specific Electronic-Nose Device Implementations
[0156] The e-nose device can be implemented in various
configurations, to include various features, and be used in various
applications. Some specific implementations are provided below.
[0157] In one specific implementation, the e-nose device includes a
sensor array of 32 sensors, composed of conducting particles
uniformly dispersed in a polymer matrix. Each polymer expands like
a sponge when exposed to a test medium (e.g., vapor, liquid, gas),
thereby increasing the resistance of the composite. The polymers
expands to varying degrees because of their unique response to
different analytes. This change in resistance varies across the
sensor array, producing a distinctive signature response.
Regardless of whether the analytes correspond to a complex mixture
of chemicals in the test sample or from a single chemical, the
e-nose device includes sufficient polymer arrays to produce a
distinct electrical "fingerprint" for the samples of interest. The
pattern of resistance changes in the sensor array is indicative of
the identity of the analytes, while the amplitude of the pattern
indicates the concentration of the analytes.
[0158] The normalized change in resistance is then transmitted to a
processor that identifies the type, quantity, and quality of the
vapor based on the detected pattern in the sensor array.
[0159] In another specific implementation, a portable e-nose device
for use in the field to detect volatile compounds is fabricated
according to the invention. The device incorporates an easy-to-read
graphic LCD with back lighting and one or more light emitting
diodes (LEDs) to indicate mode of operation. Communications ports
are provided to enable easy downloading of data into a spreadsheet
package. Rapid response tine, combined with easy one-button
operation, provide an effective and accurate measurement of the
samples. Power is supplied by replaceable or rechargeable
batteries. Housed in a robust, water-resistant case, the portable
e-nose device is suitable for various environments.
[0160] In yet another specific implementation, the e-nose device is
designed to acquire and store data collected from 32 independent
sensor elements. The e-nose device includes a 32-channel sample
chamber with inlet/outlet ports, a pump, a 3-way solenoid switch, a
LCD, push buttons, LED, a humidity probe, a temperature probe, and
a digital interface.
[0161] The power supply is designed for a 9-volt DC input. A
rectifying diode is added for circuit protection. Two on-board
5-volt linear regulators are utilized for the analog and digital
circuitry, respectively. A high precision buried Zener diode is
provided to supply a +2.5 volt reference. The overall design is a
mixed 3V and 5V design for reduced power consumption in a handheld
device.
[0162] The sample chamber houses 32 sensor elements deposited on
four ceramic substrates, each with eight sensor elements. The
substrates are fabricated using hybrid microelectronic co-fired
ceramic (alumina) processes. Electrodes and contacts are deposited
as thick films using screen-printing techniques. Resistive paths
can be provided (e.g., three paths) to be used as heating elements.
On the backside of the substrate, a surface mount thermistor can be
placed to form a heating/cooling control loop.
[0163] An inlet port is provided and a baffle can be inserted to
fan out the incoming sample stream. The outlet port is respective
to ambient barometric pressures. The sample chamber can be
fabricated of Teflon and is airtight, and is mount to the PCB. An
on-board pump can push the sample flow into the sample chamber at
pressures slightly higher than 14.7 psi. The on-board 3-way
solenoid switch can switch under processor control between a known
reference source (i.e., to "re-zero" or recalibrate as necessary)
and an unknown test sample. The four ceramic substrates are
inserted in two 20-pin, 50-mil spacing, dual row connectors. The
spacing between the rows is 100 mils. A temperature probe is
inserted into one connector and a humidity probe is inserted into
the other. The temperature and humidity probes are used for
diagnostics.
[0164] A biasing network can been implemented that biases the
chemically sensitive resistor in a DC mode of operation. The
network is a ratiometric network that is easy to implement and
stable, and offers a wide dynamic range.
[0165] It has been shown that 50 PPM changes in electrical
resistance of the chemically sensitive can be measured. Further,
baseline changes greater than .+-.50% can be accounted for with
minimal change in applied power, as shown in Table 1.
1TABLE 1 Detectable Changes in Resistance for Various Baseline
Resistances Baseline Vout Applied Power Resolution 15K
(-.DELTA.50%) 0.326 0.047 18 bits 20K (-.DELTA.33%) 0.417 0.043 18
bits 25K (-.DELTA.17%) 0.500 0.040 17 bits 30K, nominal 0.577 0.037
17 bits resistance 35K (+.DELTA.17%) 0.648 0.034 17 bits 40K
(+.DELTA.33%) 0.714 0.032 17 bits 45K (+50%) 0.776 0.030 17
bits
[0166] Assuming that Johnson noise is the dominant noise source, it
is possible to calculate an average noise voltage of 0.3 .mu.V over
a 10 Hz bandwidth and can thus detect these step changes. By
keeping the current low (i.e., <25 .mu.A) the 1/.function. noise
is reduced. In general, the biasing scheme is a constant voltage,
DC system. The current is limited to micro-amperes (.mu.As) per
sensor element and the applied power is in the order of micro-watts
(.mu.Ws). For added flexibility the current is limited and the
output voltage is scaled by resistors.
[0167] The handheld sensing apparatus of the present invention was
used to sense a series of four (4) homologous ester analytes. The
analytes sensed were the ethyl esters of propionate, butyrate,
valerate, and hexanoate. The response data was then analyzed using
principal component analysis. Principal Component Analysis (PCA) is
a powerful visualization tool that provides a way to reduce the
dimensionality of the data. PCA finds linear combinations of the
original independent variables that account for maximal amounts of
variation and provides the best possible view of variability in the
independent variable block. Natural clustering in the data is
readily determined.
[0168] FIG. 15 shows a graph of a principal component analysis of
the responses to a series of esters using the handheld apparatus of
the present invention. As shown in FIG. 15, the ester analytes were
well discriminated by the handheld device of the present
invention.
[0169] Analytes and Applications of the E-nose Device
[0170] Analytes detectable by the e-nose device of the invention
include, but are not limited to, alkanes, alkenes, alkynes, dienes,
alicyclic hydrocarbons, arenes, alcohols, ethers, ketones,
aldehydes, carbonyls, carbanions, heterocycles, polynuclear
aromatics, organic derivatives, biomolecules, microorganisms,
bacteria, viruses, sugars, nucleic acids, isoprenes, isoprenoids,
and fatty acids and their derivatives. Many biomolecules, such as
amino acids, are amenable to detection using the sensor arrays of
the invention.
[0171] The e-nose device can be used to enable medical and dental
care-providers to quickly and accurately identify the chemical
components in breath, wounds, and bodily fluids to diagnose a host
of illness including infections and metabolic problems. For
example, the e-nose device can be used to test for skin conditions,
for anesthesia administration, or to determine time of ovulation in
fertility treatment. Alternatively, the handheld device can
classify and identify microorganisms, such as bacteria.
[0172] The e-nose device can be used to locate an odor to identify
a complicated system or state of matter, and can offer versatility
and reliability absent from conventional environmental or chemical
monitoring devices. Advantageously, the device can be used for
profiling a chemical environment in a hazardous materials situation
and to assist emergency crews to accurately select fire retardant,
containment strategies, and protective gear.
[0173] The e-nose device can be used to detect leaks in pipelines
and storage containers.
[0174] The e-nose device can be used in food quality and processing
control. For example, the device can be used to spot test for
immediate results or to continually monitor batch-to-batch
consistency and spoilage in various stages of a product, including
production (i.e., growing), preparation, and distribution. The
device can also be used in disposable packaging to providing an
objectivity that is absent from conventional spoilage, freshness,
and contamination monitoring techniques.
[0175] The e-nose device can also be used in protecting the
elderly, who tend to lose sense of smell over time. The device can
be used to reduce the risk of food poisoning or the ingestion of
spoiled food, and can be integrated with household appliances, such
as refrigerators and microwave ovens.
[0176] The e-nose device can be used in a wide variety of
commercial applications including, but not limited to:
[0177] applications such as utility and power, oil/gas
petrochemical, chemical/plastics, automatic ventilation control
(cooking, smoking, etc.), heavy industrial manufacturing,
environmental toxicology and remediation, biomedicine,
cosmetic/perfume, pharmaceutical, transportation, emergency
response and law enforcement,
[0178] detection, identification, and/or monitoring of combustible
gas, natural gas, H.sub.2S, ambient air, emissions control, air
intake, smoke, hazardous leak, hazardous spill, fugitive emission,
hazardous spill,
[0179] beverage, food, and agricultural products monitoring and
control, such as freshness detection, fruit ripening control,
fermentation process, and flavor composition and
identification,
[0180] detection and identification of illegal substance,
explosives, transformer fault, refrigerant and fumigant,
formaldehyde, diesel/gasoline/aviation fuel, hospital/medical
anesthesia & sterilization gas,
[0181] telesurgery, body fluids analysis, drug discovery,
infectious disease detection and breath applications, worker
protection, arson investigation, personal identification, perimeter
monitoring, fragrance formulation, and
[0182] solvent recovery effectiveness, refueling operations,
shipping container inspection, enclosed space surveying, product
quality testing, materials quality control, product identification
and quality testing.
[0183] It should be appreciated from the foregoing description that
the present invention provides an improved vapor sensing instrument
that not only is sufficiently small and lightweight to be handheld,
but also is modular so as to allow the device to be conveniently
adapted for use in sensing the presence and identity of a wide
variety of specified vapors.
[0184] Although the invention has been described in detail with
reference to the presently preferred embodiments, those of ordinary
skill in the art will appreciate that various modifications can be
made without departing from the invention. Accordingly, the
invention is defined only by the following claims.
* * * * *