Electrochemical gas sensor and method of making the same

Details Electrochemical gas sensor and method of making the same Electrochemical gas sensor and method of making the same

1999-07-15

2001-07-24

Whitehead, Jr., Carl (Department: 2822)

Active solid-state devices (e.g., transistors, solid-state diode

Responsive to non-electrical signal

C257S428000

Reexamination Certificate

active

06265750

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed generally to an electrochemical gas sensor, and more particularly to an electrochemical gas sensor in which a portion of the components are formed using microelectromechanical systems technology.
2. Background of the Invention
Electrochemical gas sensors are typically employed in monitoring equipment, such as in equipment used in medical applications, to measure the concentration of a particular gas in a gas sample. Such equipment typically includes a display to indicate numerical readings of gas concentrations and typically provides output waveforms corresponding to the gas concentrations.
FIG. 1
illustrates a typical electrochemical gas sensor
10
of the relevant art. The sensor
10
includes a housing
12
which contains the components of the sensor
10
. A sensing electrode
14
may be constructed of, for example, a noble metal such as silver. A counter electrode
16
may be constructed of, for example, lead. An electrolyte
18
such as, for example, an aqueous solution of potassium hydroxide, fills the housing
12
. Together, the sensing electrode
14
, counter electrode
16
, and electrolyte
18
form an electrochemical cell. An expansion membrane
20
allows for expansion and contraction of the electrolyte
18
without damaging the sensor
10
. A diffusion barrier
22
, such as a membrane made of fluoropolymer resin sold under the trade name Teflon®, a registered trademark of E.I. Du Pont de Nemours and Company, is adjacent the sensing electrode
14
, and limits the diffusion rate of the gas to be measured by the sensor
10
.
Typical relevant art sensors
10
are manufactured serially. That is, the sensors
10
are manufactured from different and discrete components according to many assembly and sealing processing steps. Thus, there is little cost benefit in manufacturing sensors
10
in high volume quantities. In addition, conventional sensors are often relatively large, about ten cubic centimeters, making them too intrusive for many applications.
The performance of relevant art sensors
10
is also limited by the characteristics of the discrete components of the sensor
10
, as well as the required assembly process. The diffusion barrier
22
of the sensor
10
limits the capability of the sensor
10
to monitor rapid changes in gas concentrations: the thicker the diffusion barrier
22
, the slower the response time of the sensor
10
. Typical relevant art sensors
10
have a diffusion barrier
22
of at least five to six microns. A typical response time for such a relevant art sensor
10
is approximately 500 ms. Such response times may not be acceptable for many applications. Moreover, the minimum thickness of the diffusion barrier
22
is limited to the availability of materials from commercial suppliers and the handling requirements during conventional sensor assembly. Thus, the response times of relevant art electrochemical gas sensors are limited to values which may not be fast enough for some applications.
In addition, typical relevant art sensors
10
are temperature and pressure dependent, and do not allow for integration of electrical systems to compensate for the effects of temperature and pressure.
Accordingly, there exists a need in the relevant art for an electrochemical gas sensor which is less expensive to produce and which is smaller in size. There also exists a need for an electrochemical gas sensor which realizes faster response times than relevant art sensors in response to rapid changes in the concentration of the gas to be measured. There also exists a need for an electrochemical gas sensor which allows for the integration of other sensing elements and electronic circuits.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to an electrochemical gas sensor. The electrochemical gas sensor includes a substrate defining an opening therethrough, a sensing electrode connected to a first surface of the substrate and adjacent a first end of the opening, a diffusion barrier connected to the sensing electrode, a counter electrode adjacent a second end of the opening, and an electrolyte located in the opening between the sensing electrode and the counter electrode.
The present invention represents a substantial advance over relevant art electrochemical gas sensors. The present invention has the advantage that it can be manufactured at a lower cost of production in comparison to relevant art gas sensors. The present invention also has the advantage that the size of the sensor is significantly reduced in comparison to relevant art sensors. The present invention has the further advantage that it has a fast response time in response to changes in the concentration of input gas. The present invention also has the advantage that it allows for the integration of compensating electronics and other electrical circuits. These and other advantages and benefits of the present invention will become apparent from the Detailed Description of the Invention hereinbelow.


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patent: 2267348 (1993-01-01), None

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