U.S. patent application number 11/508089 was filed with the patent office on 2008-02-28 for low cost pressure sensor for measuring oxygen pressure.
Invention is credited to Scott Goodman, Anthony D. Kurtz.
Application Number | 20080047352 11/508089 |
Document ID | / |
Family ID | 39059408 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080047352 |
Kind Code |
A1 |
Kurtz; Anthony D. ; et
al. |
February 28, 2008 |
LOW COST PRESSURE SENSOR FOR MEASURING OXYGEN PRESSURE
Abstract
A low cost sensor assembly for measuring oxygen pressures
contains a transistor header. The transistor header has terminal
pins extending therefrom. The transistor header co-acts with a
first circuit insulator board. The first circuit board has
deposited thereon four hand mirror shaped contact areas each one
associated with one of the terminal pins of the transistor header.
The top portion of each contact areas has an aperture with the
extending arm of the area directed towards the center of the board.
The board is epoxied to the transistor header with the terminal
pins of the header extending into the apertures of the contact
board. A second contact board is then epoxied to the first contact
board. The second contact board has a series of four apertures
located at the center. Each of the apertures of the second board
contacts the handle portion of the mirror patterns of the first
board. A leadless piezoresistor sensor assembly is then positioned
and secured to the second board whereby the terminals from the
sensor assembly align with each of the apertures in the second
board. The terminals of the sensor assembly are apertures filled
with a conductive glass metal frit and each filled aperture makes
contact with a terminal of the sensor. The configuration has all
conductive terminals of the entire device completely isolated and
insulated from the oxygen environment, thus preventing ignition of
the oxygen.
Inventors: |
Kurtz; Anthony D.; (Saddle
River, NJ) ; Goodman; Scott; (Wayne, NJ) |
Correspondence
Address: |
Howard IP Law Group
P.O. Box 226
Fort Washington
PA
19034
US
|
Family ID: |
39059408 |
Appl. No.: |
11/508089 |
Filed: |
August 22, 2006 |
Current U.S.
Class: |
73/753 |
Current CPC
Class: |
G01L 9/0055 20130101;
G01L 19/147 20130101; G01L 19/148 20130101; G01L 19/0084 20130101;
G01L 9/0042 20130101 |
Class at
Publication: |
73/753 |
International
Class: |
G01L 9/00 20060101
G01L009/00 |
Claims
1. A pressure transducer, comprising: a header having a top and
bottom surface and having a plurality of terminal pins extending
from said top surface to said bottom surface, a first circuit board
having a top and bottom surface, with said bottom surface
positioned on said top surface of said header, said first board
having one aperture for each of said terminal pins located on said
top surface with said associated aperture surrounding said
associated pin, each of said apertures surrounded by a contact area
with each contact area having an extending conductive arm directed
toward the center of said board, a second circuit board having a
top and bottom surface, with said bottom surface positioned on the
top surface of said first board, said second board having a
plurality of apertures located about the center of said second
board and with each aperture positioned to overlie an associated
conductive arm of said first board, a pressure sensor having an
array of pressure responsive devices located thereon and having a
top surface for receiving a pressure and a bottom surface
positioned on said second board about the center thereof, said
bottom surface having terminal pads associated with said array with
each pad overlying an associated aperture of said second board, a
conductive material deposited in said apertures of said second
board to enable conductive contact to said terminal pads of said
sensor said conductive material in each aperture contacting said
associated extending conductive arm to thereby electrically connect
each sensor pad to each of said header terminal pins.
2. The pressure transducer according to claim 1, further including
a tubular member having a top and a bottom opening, with said
bottom opening positioned about the periphery of said header, with
said top opening serving as a pressure port to enable a pressure to
be monitored to be applied to said pressure sensor.
3. The pressure transducer according to claim 1, wherein said
header is a transistor header selected as TO5 or TO8 header.
4. The pressure transducer according to claim 1, wherein said first
circuit board is fabricated from an insulating material, with said
first circuit board secured to said top surface of said header by
an epoxy bond.
5. The pressure transducer according to claim 1, wherein said
second circuit board is fabricated from an insulating material,
with said second circuit board secured to said first circuit board
by an epoxy bond.
6. The pressure transducer according to claim 2, wherein said
tubular member has a top narrow tubular section extending to a
larger bottom tubular section, with said bottom tubular section
secured at the periphery to said header.
7. The pressure transducer according to claim 1, wherein said
pressure sensor is a semiconductor pressure sensor chip having four
piezoresistive elements mounted on an active area of said sensor
and arranged in a Wheatstone bridge array with each terminal of
said bridge directed to an associated terminal pad of said sensor,
said sensor having said piezoresistors dielectrically isolated with
said chip being secured to said second circuit board by an epoxy
bond.
8. The pressure transducer according to claim 7, wherein said
piezoresistive elements are p-type monocrystalline silicon
piezoresistors.
9. The pressure transducer according to claim 1, wherein said
conductive material is a conductive epoxy.
10. The pressure transducer according to claim 1, wherein said
pressure to be monitored is the pressure provided by a source of
oxygen.
Description
FIELD OF THE INVENTION
[0001] This invention relates to pressure sensors in general and
more particularly to a low cost pressure sensor for measuring
oxygen pressure and methods of fabricating the same.
BACKGROUND OF THE INVENTION
[0002] Pressure transducers are utilized and employed in a wide
variety of applications. One application for the use of a pressure
transducer involves measuring oxygen pressures. In aircraft or in
other environments oxygen masks are employed in dangerous
situations. The oxygen masks can be released and used by a
passenger in the event of a technical breakdown whereby the
aircraft may lose pressure or in other situations. In employing
such devices, one must measure the actual pressure of the oxygen as
it enters each mask. One can monitor the entire pressure of the
oxygen on the aircraft, but this would not be sufficient and it is
preferable that one measure the pressure of the oxygen at each
mask. In this manner one can be assured that the proper pressure is
being furnished together with the oxygen. In many such devices, the
oxygen instead of flowing continuously, is basically pulsed and
therefore bursts of oxygen are sent at predetermined repetitive
intervals. In this manner, the average pressure imparted to the
oxygen mask should be known and therefore a pressure transducer or
a sensor is employed in order give an accurate measure of the
pressure supplied to the mask. If the pressure is not adequate, a
warning light or other indication can be provided indicating that
the passenger should use another mask or use other facilities.
[0003] The aspect of monitoring oxygen pressure in an aircraft or
other environment is very desirable. It may also be desirable to
measure oxygen pressure in other types of oxygen devices such as in
hospital environments and so on where oxygen is also supplied to a
patient or other user. As one can ascertain, measuring the pressure
of oxygen creates certain problems. Any transducer utilized in such
an environment must be capable of being cleaned to remove Organic
materials and to have no electrical current carrying members in
contact with the oxygen. As one can ascertain, any spark or
exposure to electrical current can ignite the oxygen thus leading
to a disaster. A pressure transducer utilized in such environments
must be fabricated to prevent the above-noted problems. It is a
further desire to provide such a pressure transducer at low cost
due to the large number of transducers that are employed in an
aircraft having a large number of passenger seats and
positions.
SUMMARY OF THE INVENTION
[0004] A pressure transducer, comprising a header having a top and
bottom surface and having a plurality of terminal pins extending
from the top surface to the bottom surface, a first circuit board
having a top and bottom surface with the bottom surface, positioned
on the top surface of the header, the first board having one
aperture for each of the terminal pins located on the top surface
with the associated aperture surrounding the associated pin, each
of the apertures surrounded by a contact area with each contact
area having an extending conductive arm directed toward the center
of the board, a second circuit board having a top and bottom
surface with the bottom surface positioned on the top surface of
the first board, the second board having a plurality of apertures
located about the center of the second board and with each aperture
positioned to overlie an associated conductive arm of the first
board, a pressure sensor having an array of pressure responsive
devices located thereon and having a top surface for receiving a
pressure and a bottom surface positioned on the second board about
the center thereof, the bottom surface having terminal pads
associated with the array with each pad overlying an associated
aperture of the second board, a conductive material deposited in
the apertures of the second board to enable conductive contact to
the terminal pads of the sensor the conductive material in each
aperture contacting the associated extending conductive arm to
thereby electrically connect each sensor pad to each of the header
terminal pins.
BRIEF DESCRIPTION OF THE FIGURES
[0005] FIG. 1 is a cross-sectional view of the pressure transducer
for measuring oxygen according to an embodiment of the
invention.
[0006] FIG. 2 is a cross-sectional view of a sensor employed in
conjunction with an embodiment of the invention.
[0007] FIG. 3 consists of FIGS. 3A, 3B and 3C which respectively
show a sensor diaphragm, a cross-sectional view of the sensor and a
top-view of the piezoresistive elements found on a sensor.
[0008] FIG. 4 is a cross-sectional perspective exploded view
showing each individual part of the sensor depicted in FIG. 1.
[0009] FIG. 5 consists of FIGS. 5A and 5B which respectively show a
top-view of a circuit board and a cross-sectional view of the same
circuit board used in an embodiment of the invention.
[0010] FIGS. 6A and 6B show a top-plan view and a cross-sectional
view, respectively, of another circuit board used in an embodiment
of the invention.
[0011] FIGS. 7A-7E depicts the various steps utilized in
fabricating a pressure transducer according to an embodiment of the
invention.
[0012] FIG. 8 is a schematic circuit diagram of an oxygen pressure
sensor and associated alarm circuitry.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring to FIG. 1 and particularly to FIG. 1A there is
shown a cross-sectional view of a low cost pressure sensor 10
particularly adapted for measuring oxygen pressures. The pressure
sensor 10 has a metallic can 18 which basically has a tubulation
portion 27 extending to a greater diameter portion 28. The
tubulation portion 27 extends into a larger diameter portion 28.
The portion 28 has an extending flange 19. The metallic can 10 as
seen in FIG. 1A has a bottle shape having the tubulation or neck 27
which typically is on the order of a quarter of an inch in length
and one-eighth of an inch in diameter. The top opening 11 serves as
a pressure port for receiving oxygen pressure. The larger diameter
portion 28 surrounds the pressure sensor 24 and is secured to a
transistor header 21. A perspective view of the metallic can 18 is
shown in FIG. 1B.
[0014] The transistor header 21 is a typical transistor header and
has a metal base portion 29 which has extending terminal pins 25
and 26. Such transistor headers are well known and for example a
TO5 header or a TO8 header can be used for header 21. Such headers
typically have at least four pins as 25 and 26. Typically the metal
can 18 is discharged welded via flange 19 to the header flange 35.
The header 21 has mounted on the top surface thereof a first
circuit board or an insulative substrate 20. The board 20 has
apertures into which the pins as 25 and 26 extend. The board is
mounted and secured to the top surface of the transistor header
with an epoxy material. Such epoxy materials are well known.
Positioned on board 20 is a second board 30 which is mounted and
secured to board 20 with an epoxy bond. As will be explained, both
the circuit board 20 and circuit board 30 have apertures for
accommodating the pins of the transistor header as pins 25 and 26,
which pins eventually will be connected to the outputs of the
piezoresistive sensor. The piezoresistive sensor is depicted in
FIG. 1A by reference numeral 24. Essentially the sensor is a
leadless sensor as the type available from Kulite Semiconductor,
the assignee herein. The leadless sensor 24 is mounted and secured
to board 30 by an epoxy bond. There is also a layer of epoxy 31
which surrounds the peripheral edge of the sensor. The sensor
contains a glass metal frit 16 which frit contacts the terminal
pads of the sensor. A conductive epoxy 17 enables one to make
contact with the terminal pins 25 and 26 of the transistor header
21.
[0015] A more detailed view of a typical piezoresistive sensor 24
is shown in FIG. 2. As seen the piezoresistive sensor has p-type
monocrystalline silicon piezoresistors 32. The piezoresistors 32
are formed on a sensor wafer 35, which for example may be a wafer
of silicon. The entire structure, as indicated, is secured to the
top surface of the board 30 by means of an epoxy. The epoxy also
forms a surrounding peripheral band 31 about the sensor element 24.
The sensor element includes a glass contact wafer 36 which is
bonded to the silicon wafer 35. There are terminal apertures as
depicted which are filled with a conductive glass metal frit 16.
Glass metal frits are conductive and essentially enable one to make
contact to the piezoresistors located on the silicon wafer as is
known. The entire sensor 24 is bonded to the board 30 by means of
an epoxy bond. An epoxy 17 is a conductive epoxy and therefore
makes contact to the metal glass frits as contained in the
semiconductor wafer. The epoxy 17 fills the apertures of board 30
and makes contact with the contact pads of the sensor 24.
[0016] The above-noted wafer depicted in FIG. 2 essentially is
referred to as a leadless dielectrically isolated sensor chip. The
assignee herein has a number of patents which fully describe such a
sensor. For example, reference is made to U.S. Pat. No. 5,973,590
entitled "Ultra-Thin Surface Mount Wafer Sensor Structures and
Methods of Fabricating the Same", issued on Oct. 26, 1999 to A. D.
Kurtz et al and assigned to the assignee herein. That patent
depicts a sensor chip which may be employed as the chip of FIG. 2.
For example, reference is made to FIG. 10 of the above-noted patent
which shows a suitable sensing structure which may be employed for
the sensor depicted in FIG. 2. Reference is also made to U.S. Pat.
No. 6,210,989 which is a divisional of the above-noted patent and
which issued on Apr. 3, 2001 having the same title as indicated
above and also assigned to the assignee herein. Both patents
disclose semiconductor sensor devices which include a semiconductor
diaphragm member which is depicted in FIG. 2. The recesses as 37
which form an active area for the entire transducer which active
area functions as a diaphragm and deflects upon application of a
force to the sensor 24.
[0017] Also surrounding the transducer is a top-ring member 40
which is secured to the sensor structure by conventional means. In
any event, as one can ascertain the sensor of FIG. 2 as further
noted in the above-noted patents contain four piezoresistors which
are connected in a Wheatstone bridge configuration. The Wheatstone
bridge has four terminals which are directed via the associated
glass metallic frit contacts 16 to the conductive epoxy terminals
17 and eventually come into contact with terminal pins such as 25
and 26 of the transistor header 21. This therefore enables one to
provide an output for the Wheatstone bridge as well as providing a
biasing to the bridge. This is conventional and as one can see from
the above-noted patents, which are incorporated herein, the devices
are referred to as leadless sensing devices because of the fact
that there are no wires directed from the devices. The means of
making connections to the devices reside in the apertures which
contain the glass metal frit which are conductive frits as well as
the conductive epoxies which direct the terminals of the Wheatstone
bridge to the output connector of the device. FIG. 1B shows a
perspective view of the metal can 18 depicted in FIG. 1A showing
the tubular portion 27 which has the pressure port 11 at the top
end and which as shown in FIG. 1A extends into portion 28 which has
the flange 19 which is welded to the corresponding flange 35 of the
transistor header 21 by a discharge weld 22.
[0018] Referring to FIG. 3 there is shown in FIG. 3A a top view of
the semiconductor sensor depicted in FIG. 1A. The semiconductor
sensor 24 has a central boss 61 which acts as a stop. Surrounding
the boss 61 are thinned areas as recesses 62. These thinned areas
will deflect upon application of a force to the device. These areas
are known as the active area as compared to, for example, area 60
which is a peripheral area known as the inactive area. As seen in
FIG. 3B a glass wafer or other device is mounted to the silicon
wafer 44 by means of a fusion bond. The glass wafer 60 is an
insulating wafer and is used for mounting purposes. As seen in FIG.
3B the piezoresistors 41 are shown as well as the glass frit filled
apertures 42. The apertures 42 are filled with a conductive metal
glass frit and the metal glass frit makes contact to the terminals
of the Wheatstone bridge as fully described in the above-noted
patents. FIG. 3C shows four piezoresistor sensors as 50, 52, 53 and
54 connected to associated terminal pads as 51 and 57 to form a
Wheatstone bridge. FIG. 3C is taken from FIG. 3B with the wafer 43
omitted and looking down on the piezoresistive sensors. Typically
shown, the sensors as 50, 52, 53 and 54 are serpentine and operate
to vary resistance upon application of an applied force to the
device. The applied force is applied via the pressure port 11 which
is the top open surface of the tubular portion of the metallic can
18. This is shown in FIG. 1B where pressure (P) is applied to the
aperture 11 which is the pressure port.
[0019] Referring to FIG. 4 there is shown an exploded
cross-sectional view of the various components depicted in FIG. 1
prior to installing the same. Thus there is shown the metal can 18
having the tubular portion 27 with a pressure port 11 defined by
the top open surface. The tubular portion 18 is narrower than the
end portion 28 which terminates in an extending flange 19. It is
noted that the can as depicted in FIGS. 1 and 4 essentially appears
like a cross section of a typical bottle where the neck of the
bottle is depicted by reference numeral 18 and the body of the
bottle by reference numeral 28. There is shown the chip 24 prior to
being mounted on the board 30, which board 30 as indicated, is
mounted on board 20. The transistor header 21 is shown with pins 25
and 26 emanating therefrom. The pins typically as 25 and 26 are
secured to the metallic header 21 by means of glass enclosures as
for example, 65 and 66. Pins may be secured to the transistor
header by other means.
[0020] Referring to FIG. 5A in conjunction with FIG. 5B, there is
shown a depiction of the board 20. As seen the board 20 has an
alignment notch 71. The board also contains four terminal
copper-plated areas as 72, 73, 74 and 75. Each area has a central
aperture as aperture 70 associated with area 74. The board 20 is
typically fabricated from an insulating material such as a Kapton
or a ceramic or other insulating material. The areas as for example
72, 73, 74 and 75 are copper-gold-plated areas and are formed on
the board by means of photolithographic techniques. Such techniques
are well known in the semiconductor art. As seen the four pads,
each appear as a hand mirror configuration with a central aperture
70. The arms of the mirror as 76 and 77 extend towards the center
78 of the board 20. The board thickness 20 is typically 0.3 inches
thick where the apertures are typically 0.02 inches and are equally
spaced on the board 20. The board as indicated is metallized by
typical techniques and preferably the board is fabricated from
Kapton or a ceramic material such as alumina or some other suitable
material. FIG. 5B shows a cross-section of the board showing the
through aperture 70 each associated with the hand mirror like
contact pads as 72, 73, 74 and 75.
[0021] Referring to FIG. 6A there is shown a top-plan view of the
board 30 which also has an alignment notch 80. The board 30
contains apertures as 81, 84, 85 and 86 with each aperture bounded
by a L-shaped mark 82. The apertures 81 are shown more clearly in
the cross-sectional view depicted in FIG. 6B. The L-shaped members
as 82 are alignment marks to enable a proper positioning of the
sensor structure 24 on the board 30. The board has four apertures
(81, 84, 85, and 86) which are in one embodiment, basically 0.015
inches in diameter. These are through holes and are equally spaced.
These apertures will accommodate the suitable terminals of the
sensor element 24. The board 20 accommodates the terminal pins from
the transistor header as pins 25 and 26 (FIG. 4). This is also
clearly depicted in FIG. 1A where the pins extend through the
apertures as 70. The elongated arms 76 and 77 (FIG. 5A) associated
with each of the pad areas overlie the apertures as 81 and 82 of
the board 30 when boards 20 and 30 are positioned as shown. These
apertures are filled with the conductive epoxy 17. Therefore, the
conductive epoxy 17 which fills the apertures as 81, 82 makes
contact to the terminals of the sensor chip as for example those
terminals which are filled with the glass metal frit 16. Thus, the
terminals filled with the glass metal frit 16 make contact with the
conductive filled apertures 81, 84 and 85. The conductive epoxy 17
makes contact with the elongated ends 76 and 77 of the hand mirror
shaped terminal pads 72, 73, 74 and 75 of FIG. 5A. The apertures of
terminal board 20 accommodate contact with the pins 25 and 26 of
the transistor header. Thus, circuit boards 20 and 30 interface
with the sensor chip enabling one to contact each of the terminals
of the Wheatstone bridge array which is located on the sensor chip.
All the terminals which emanate from the sensor are completely
surrounded and enclosed and make no contact with the oxygen
environment. This therefore provides a sensor structure which is
completely isolated from the environment and if any spark occurs it
cannot be directed to the oxygen environment because of the way the
sensor is mounted and isolated in the assembly. It is seen that the
conductive epoxy terminals as 17 are all surrounded by the board 20
and 30 while the glass metal frit contacts as 16 associated with
the sensor are all surrounded by the glass contact wafer of the
sensor. It is thus seen that the entire sensor and all electrical
carrying leads are totally isolated in the configuration and
contact is made as described above via the circuit boards 20 and 30
depicted respectively in FIG. 5 and FIG. 6.
[0022] Referring to FIG. 7 there is shown a typical assembly
procedure for fabricating the above-noted device. FIG. 7A depicts
the first step in the process where a transistor header 21 having
terminal pins 25 and 26 is first shown. The transistor header as
indicated above may be a TO5 header or a TO8 header or any
transistor header. While two pins 25 and 26 are shown it is noted
that there are at least four pins associated with a typical
transistor header. As indicated the pins as 25 and 26 will
eventually contact the terminal pads of the semiconductor sensor
wafer 24. Referring to FIG. 7B there is shown a second step in the
process where the board 20 is now mounted to the transistor header
by means of an epoxy bond. Also shown in this second step are
conductive epoxy areas as 90 and 91. The conductive epoxy areas 90
and 91 are employed to make contact with the hand mirror like
conductive areas 72 and 73 (FIG. 5A). Therefore, the conductive
areas assure that terminal pins 25 and 26 for example are all
conductively connected via the aperture 70 to the circuit board 20.
FIG. 7C depicts a third step in the process, where the circuit
board 30 having apertures 81 and 85 is placed upon the circuit
board 20. The circuit board 30 is again mounted on circuit board 20
with a suitable epoxy. The apertures 81 and 85 are shown. FIG. 7D
depicts a fourth step in the process. In step 4, apertures 81 and
85 associated with circuit board 30 are filled with a conductive
epoxy 17. The sensor 24 is placed thereon having its apertures
filled with a glass metal frit 16. The glass metal frit 16 makes
contact with the conductive epoxy 17 which in turn makes contact
with the extending arms 76, 77 associated with the hand mirror like
terminal pads 72, 73, 74 and 75 of board 20, thereby enabling the
four terminals of the Wheatstone bridge on the sensor wafer to be
connected to an associated terminal pin as 25 and 26 of the
transistor header 21. Step 5 shows the final assembly where the can
18 is now welded to the extending flange 35 of the transistor
header 21 via a weld 22. As one can ascertain, FIG. 7E shows the
final transducer structure depicting boards 20 and 30 and depicting
the pressure port 11 associated with the tubular portion of the
metal can 18.
[0023] Referring to FIG. 8 there is shown a simple circuit diagram
depicting one use of an oxygen pressure sensor according to an
embodiment of this invention. As seen in FIG. 1 reference numeral
100 depicts a Wheatstone bridge having piezoresistors 101, 102, 103
and 104. This Wheatstone bridge array is the same array as would be
fabricated on sensor chip 24 shown in FIG. 1A and FIG. 2. As
indicated, each of the sensors as 101, 102, 103 and 104 is a
piezoresistive sensor and located on the semiconductor wafer 24.
The piezoresistive sensors may be p-type monocrystalline silicon
piezoresistors for example. The Wheatstone bridge array as shown in
FIG. 8 is the typical array which is found on the sensor wafer as
24 of FIG. 1. The terminals as shown for example as terminals 120,
121, 122 and 123 are the four terminals of the Wheatstone bridge
which eventually connect and are directed to the terminal pins of
the transistor header. The output of the Wheatstone bridge is
directed to an operational amplifier 105 which produces an
amplified version of the voltage. When a pressure (P) is applied to
the sensor array, the sensors which are positioned on the active
area of the diaphragm change resistance as the diaphragm deflects.
In this manner, the output voltage is a direct indication of the
magnitude of pressure. For an oxygen pressure sensor the output of
operational amplifier is directed to a high pressure
detector/monitor module 107 and a low module 108. Each module may
be associated with a timer 106. The function of modules 107 and 108
is to determine whether the pressure as applied to the Wheatstone
bridge is within desirable limits. If the pressure is too low, the
pressure monitor 108 will recognize the low voltage and if it
maintains low for a predetermined period as determined by timer 106
an alarm 110 will be sounded. The alarm 110 may be a visual alarm
such as a light or other indicator and may be located in the
cockpit of the plane or at some other remote location. In a similar
manner, if the pressure is too high, this will be detected by the
high pressure detector 107 and if the pressure remains too high for
a predetermined period determined by timer 106 then a high pressure
alarm 109 will be activated. It is understood that the monitoring
of the Wheatstone bridge can be implemented by means of a
microprocessor and a suitable program can be written regarding the
same. FIG. 8 is merely included to show that the pressure sensor
100 which is monitoring the pressure of oxygen in an environment is
associated normally with circuitry to determine whether or not the
pressure operates within suitable limits. The circuit of FIG. 8 is
merely by way of an example and not intended to be limiting in any
respect. It is also again indicated that the oxygen pressure sensor
as described above is utilized in the circuit 100 and essentially
the main aspect and purpose of the sensor is to assure that there
can be no electrical contact with the oxygen environment.
Therefore, any current carrying lead or any electrical arc will not
be propagated to the oxygen environment because of the structure of
the pressure transducer. Again, as shown, one has provided a sensor
for measuring pressure in an oxygen environment where all active or
current/voltage carrying terminals are completely isolated from the
oxygen environment by means of insulating materials as ceramic,
Kapton or insulating epoxy. These materials as employed such as
Kapton, ceramic and the epoxies are highly insulating materials and
therefore the danger of any electrical contact being made with the
oxygen environment is totally minimized. It is also seen that the
sensor is simple to construct and extremely reliable.
[0024] Thus, it should be apparent to one skilled in the art that
there may be alternative configurations and alternate embodiments
which may be employed. These include the substitution of different
materials. For example the use of glass or glass seals in lieu of
epoxy and use of other conductive materials in lieu of conductive
epoxy or glass metal conductive frit-like materials are
envisioned.
[0025] All such modifications and alterations should be apparent to
those skilled in the art and all such configurations are deemed to
be encompassed within the spirit and scope of the claims appended
hereto.
* * * * *