CA1116428A - Pressure gauge - Google Patents
Pressure gaugeInfo
- Publication number
- CA1116428A CA1116428A CA000316733A CA316733A CA1116428A CA 1116428 A CA1116428 A CA 1116428A CA 000316733 A CA000316733 A CA 000316733A CA 316733 A CA316733 A CA 316733A CA 1116428 A CA1116428 A CA 1116428A
- Authority
- CA
- Canada
- Prior art keywords
- membranes
- membrane
- substrate
- recited
- sealingly engaged
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Measuring Fluid Pressure (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A capsule for use in aneroid pressure gauges comprising a pair of membranes whose peripheral edge regions are sealingly engaged to an interposed insulator substrate to define there-within a sealed, partially evacuated, space. The pair of membranes have an electrical capacitance created between them and means are provided coupled to the membranes for measuring changes in the capacitance as the distance between the membranes changes as a result of changes in pressure. The capsule is particularly suited for use in connection with an aneroid pressure gauge or barometer utilized in radiosondes.
A capsule for use in aneroid pressure gauges comprising a pair of membranes whose peripheral edge regions are sealingly engaged to an interposed insulator substrate to define there-within a sealed, partially evacuated, space. The pair of membranes have an electrical capacitance created between them and means are provided coupled to the membranes for measuring changes in the capacitance as the distance between the membranes changes as a result of changes in pressure. The capsule is particularly suited for use in connection with an aneroid pressure gauge or barometer utilized in radiosondes.
Description
111642~
This invention relates to aneroid pressure gauges or barometers and, more particularly, to aneroid pressure gauges wherein changes in pressure are indicated by changes in capacitance resulting from the deflection of the membranes defining the evacuated capsule or cell forming a component of the pressure gauge.
Aneroid pressure gauges are known which measure pressure by means of changes in the capacitance of associated components effected by the deflection of one of the membranes of the aneroid capsule forming a component of the pressure gauge. Thus, in one existing aneroid pressure gauge, an aneroid capsule or cell com-prising a pair of membranes defining a sealed evacuated space between them has one of these membranes fastened to the chassis or housing of the pressure gauge. A capacitor is provided including one fixed capacitor plate and an opposed, movable capacitor plate.
The movable membrane of the aneroid capsule is mechanically linked to the movable capacitor plate so that changes in pressure result in a deflection of the capsule membrane which results in a corres-ponding movement of the movable capacitor plate thereby changing the capacitance of the capacitor. Thus, it is the output of the capacitor which is measured in order to obtain pressure measure-ments. Such capacitance type aneroid pressure gauges are particu-larly useful in connection with radiosondes which, among other things, measure minute changes in pressure over short intervals of time.
Aneroid pressure gauges of the type described above are not entirely satisfactory, however. Thus, by virtue of the fact that the deflection of the capsule membrane is transmitted to the movable capacitor plate, of a separate capacitor the device is influenced by ambient pressure, temperature and humidity.
Additionally, such prior art devices are relatively complicated in construction since they require a relatively large number of components. For these reasons, such prior art aneroid pressure .:
,~
- 1- ~
1~164Zfi gauges are relatively expensive.
Accordingly, one object of the present invention is to provide a new and improved aneroid pressure gauge which effects changes in capacitance in accordance with changes in pressure.
Another object of the present invention is to provide such a new and improved aneroid pressure gauge which is mechanically stable and which has extremely good accuracy.
Still another object of the present invention is to provide such a new and improved aneroid pressure gauge which is relatively simple in construction and inexpensive to manufacture.
Briefly, in accordance with the present invention, these and other objects are attained by providing a capsule or cell for the aneroid pressure gauge comprising a pair of capsule membranes whose peripheral edge regions are sealingly engaged to an interposed insulator substrate to define a partially evacuated sealed space therewithin. The pair of membranes are electrically isolated from each other and have an electrical capacitance created between them.
Means are provided on the membranes for measuring changes in the capacitance between the membranes as the distance between the membranes changes as a result of changes in pressure. Thus, it is seen that the need for a separate capacitor component as described above in connection with prior art devices of this type is obviated in that changes in capacitance resulting from changes in pressure can be obtained directly from the aneroid capsule itself.
According to the present invention therefore there is provided an aneroid capsule apparatus for use in a pressure gauge comprising: a rigid substrate formed of electrically insulative material; a first self-supporting membrane formed of electrically conductive material having a peripherally extending side edge region sealingly engaged to said substrate; a second self-supporting membrane formed of electrically conductive material extending substantially parallel to and at a distance from said first mem-lli64;~t~
brane, said second membrane having a peripherally extending side edge region sealingly engaged to said substrate in electrically isolated relation to said first membrane, defining a sealed interior space between said first and second membrane which is partially evacuated, said first and second membranes having an electrical capacitance created between them and a pair of con-ductor means, each electricall.y communicating with a respective one of said electrically con~uctive membranes in a manner such that it does not extend within said sealed interior space, where-by changes in said capacitance between said membranes resulting from changes in pressure can be measured.
In one embodiment of the present invention the insulator substrate comprises a substantially planar member having first and second opposite side surfaces to which the peripheral edge regions of said first and second membranes are respectively sealingly engaged.
In another embodiment of the present invention the insulator substrate comprises a ring-shaped annular me~ber de-fining an opening therein and having first and second opposite side surfaces.
A more complete appreciation of the invention and many of the attendant advantages tnereof will be readily appreciated as the same becomes better understood by reference to the follow-ing detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 is a plan view of the aneroid capsule or cell of the pressure gauge according to the present invention;
FIG. 2 is a section view taken along line II-II of FIG. 1 illustrating the aneroid capsule of the present invention;
FIG. 3 is a front view in section of another embodiment of the aneroid capsule of the present invention; and FIG. 4 is a front section view of still another embodi-ment of the aneroid capsule of the present invention.
Referring now to the drawings wherein like reference numerals designate identical or corresponding parts throughout the several views,and, more particularly, to FIGS. 1 and 2, one embodiment of the aneroid capsule or cell of the present invention, generally designated 20, is illustrated. The capsule 20 comprises a flat, planar substrate 10 formed of an electrically insulative material, such as ceramic material. The term substrate is used herein to denote a self-supporting member which need not ne-cessarily require a supportive base. First and second membranes 21, 22, respectively, which, in the present embodiment have a circular configuration, each has its peripheral side edge region sealingly engaged to the upper and lower surfaces 13,14 of substrate lO. First and second membranes 21,22 are self supporting and are formed of a resilient electrically conductive material and each has a circumferentially extending corugated portion 16,17, respectively formed immediately inwardly of the side edge regions thereof. Such corrugated structure is per se conventional and serves to enhance the flexibility of the re-spective membranes~
l~lfi4Z8 Thus, referring to FIG. 2, firstmembrane 21 has its peripheral side edge regions sealingly affixed to the upper surface 13 of substrate 10 while the second membrane 22 is sealingly engaged at its peripherally extending side edge region to the lower surface 14 of substrate 10. During construction, the sealed spaces 23 are partially evacuated so that a pair of sealed evacuated spaces 23 are defined by the substrate 10 and the first and second membranes 21, 22, respectively.
As seen in FIC-.l, the insulator substrate 10 has a lQ substantially square configuartion having portions which extend outwardly beyond the side edge regions of the first and second membranes. ~penings ll are provided in the outwardly extending portion of substrate 10 which comprise means for attaching the capsule 20 to the chassis of the pressure gauge. Of course, it is understood that the substrate 10 may be fcrmed with other con-figurations, such as circular.
By virtue of the above-described construction of capsule 20, the latter will have a particular capacitance for any given distance between the first and second membranes 21,22. Thus,
This invention relates to aneroid pressure gauges or barometers and, more particularly, to aneroid pressure gauges wherein changes in pressure are indicated by changes in capacitance resulting from the deflection of the membranes defining the evacuated capsule or cell forming a component of the pressure gauge.
Aneroid pressure gauges are known which measure pressure by means of changes in the capacitance of associated components effected by the deflection of one of the membranes of the aneroid capsule forming a component of the pressure gauge. Thus, in one existing aneroid pressure gauge, an aneroid capsule or cell com-prising a pair of membranes defining a sealed evacuated space between them has one of these membranes fastened to the chassis or housing of the pressure gauge. A capacitor is provided including one fixed capacitor plate and an opposed, movable capacitor plate.
The movable membrane of the aneroid capsule is mechanically linked to the movable capacitor plate so that changes in pressure result in a deflection of the capsule membrane which results in a corres-ponding movement of the movable capacitor plate thereby changing the capacitance of the capacitor. Thus, it is the output of the capacitor which is measured in order to obtain pressure measure-ments. Such capacitance type aneroid pressure gauges are particu-larly useful in connection with radiosondes which, among other things, measure minute changes in pressure over short intervals of time.
Aneroid pressure gauges of the type described above are not entirely satisfactory, however. Thus, by virtue of the fact that the deflection of the capsule membrane is transmitted to the movable capacitor plate, of a separate capacitor the device is influenced by ambient pressure, temperature and humidity.
Additionally, such prior art devices are relatively complicated in construction since they require a relatively large number of components. For these reasons, such prior art aneroid pressure .:
,~
- 1- ~
1~164Zfi gauges are relatively expensive.
Accordingly, one object of the present invention is to provide a new and improved aneroid pressure gauge which effects changes in capacitance in accordance with changes in pressure.
Another object of the present invention is to provide such a new and improved aneroid pressure gauge which is mechanically stable and which has extremely good accuracy.
Still another object of the present invention is to provide such a new and improved aneroid pressure gauge which is relatively simple in construction and inexpensive to manufacture.
Briefly, in accordance with the present invention, these and other objects are attained by providing a capsule or cell for the aneroid pressure gauge comprising a pair of capsule membranes whose peripheral edge regions are sealingly engaged to an interposed insulator substrate to define a partially evacuated sealed space therewithin. The pair of membranes are electrically isolated from each other and have an electrical capacitance created between them.
Means are provided on the membranes for measuring changes in the capacitance between the membranes as the distance between the membranes changes as a result of changes in pressure. Thus, it is seen that the need for a separate capacitor component as described above in connection with prior art devices of this type is obviated in that changes in capacitance resulting from changes in pressure can be obtained directly from the aneroid capsule itself.
According to the present invention therefore there is provided an aneroid capsule apparatus for use in a pressure gauge comprising: a rigid substrate formed of electrically insulative material; a first self-supporting membrane formed of electrically conductive material having a peripherally extending side edge region sealingly engaged to said substrate; a second self-supporting membrane formed of electrically conductive material extending substantially parallel to and at a distance from said first mem-lli64;~t~
brane, said second membrane having a peripherally extending side edge region sealingly engaged to said substrate in electrically isolated relation to said first membrane, defining a sealed interior space between said first and second membrane which is partially evacuated, said first and second membranes having an electrical capacitance created between them and a pair of con-ductor means, each electricall.y communicating with a respective one of said electrically con~uctive membranes in a manner such that it does not extend within said sealed interior space, where-by changes in said capacitance between said membranes resulting from changes in pressure can be measured.
In one embodiment of the present invention the insulator substrate comprises a substantially planar member having first and second opposite side surfaces to which the peripheral edge regions of said first and second membranes are respectively sealingly engaged.
In another embodiment of the present invention the insulator substrate comprises a ring-shaped annular me~ber de-fining an opening therein and having first and second opposite side surfaces.
A more complete appreciation of the invention and many of the attendant advantages tnereof will be readily appreciated as the same becomes better understood by reference to the follow-ing detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 is a plan view of the aneroid capsule or cell of the pressure gauge according to the present invention;
FIG. 2 is a section view taken along line II-II of FIG. 1 illustrating the aneroid capsule of the present invention;
FIG. 3 is a front view in section of another embodiment of the aneroid capsule of the present invention; and FIG. 4 is a front section view of still another embodi-ment of the aneroid capsule of the present invention.
Referring now to the drawings wherein like reference numerals designate identical or corresponding parts throughout the several views,and, more particularly, to FIGS. 1 and 2, one embodiment of the aneroid capsule or cell of the present invention, generally designated 20, is illustrated. The capsule 20 comprises a flat, planar substrate 10 formed of an electrically insulative material, such as ceramic material. The term substrate is used herein to denote a self-supporting member which need not ne-cessarily require a supportive base. First and second membranes 21, 22, respectively, which, in the present embodiment have a circular configuration, each has its peripheral side edge region sealingly engaged to the upper and lower surfaces 13,14 of substrate lO. First and second membranes 21,22 are self supporting and are formed of a resilient electrically conductive material and each has a circumferentially extending corugated portion 16,17, respectively formed immediately inwardly of the side edge regions thereof. Such corrugated structure is per se conventional and serves to enhance the flexibility of the re-spective membranes~
l~lfi4Z8 Thus, referring to FIG. 2, firstmembrane 21 has its peripheral side edge regions sealingly affixed to the upper surface 13 of substrate 10 while the second membrane 22 is sealingly engaged at its peripherally extending side edge region to the lower surface 14 of substrate 10. During construction, the sealed spaces 23 are partially evacuated so that a pair of sealed evacuated spaces 23 are defined by the substrate 10 and the first and second membranes 21, 22, respectively.
As seen in FIC-.l, the insulator substrate 10 has a lQ substantially square configuartion having portions which extend outwardly beyond the side edge regions of the first and second membranes. ~penings ll are provided in the outwardly extending portion of substrate 10 which comprise means for attaching the capsule 20 to the chassis of the pressure gauge. Of course, it is understood that the substrate 10 may be fcrmed with other con-figurations, such as circular.
By virtue of the above-described construction of capsule 20, the latter will have a particular capacitance for any given distance between the first and second membranes 21,22. Thus,
2~ changes in pressure will result in a deflection of the first and second membranes 21, 22 which change the capacitance of the capsule 20 accordingly. Thus, apparatus for measuring the capacitance of the capsule 20 which, in the preferred embodiment, comprise a pair of electrical leads 27, are provided so that changes in the - capacitance of the capsule may be measured which, of course, may be converted by appropriate existinq apparatus to pressure measurements.
Thus, it is seen that according to the present invention, an extremely simple yet accurate and reliable capsule apparatus is provided whereby changes in pressure can be directly obtained by measuring the capacitance between the pair of opposed membranes 21,22 having the insulative substrate 10 interposed therebetween ;- _ 5 _ to electrically isolate the memhranes from each other. As mentioned above, the requirement of a separate capacitor component is obviated by the present invention thereby significantly reducing the cost and complexity of the device.
Referring to FIG. 3, the insulator substrate, designated 10', comprises a rin~-shaped annular member defining a circular opening 12 therewithin. First and second memhranes 21,22 have their peripheral side edge regions sealingly engaged to the upper and lower surfaces 13,14, respectively of substrate 10' at the region thereof adjacent to the opening 12. Thus, in this embodi-ment, a single evacuated space 23' is defined between first and second membranes 21,22.
Referring to FIG. 4, another embodiment of the capsule 20 of the present invention is illustrated wherein the insulator substrate 10" is also formed having a ring-shiped or annular configuration. However, in this case, the peripheral side edge regions of membranes 21,22 are sealingly engaged to the same side 13 of substrate 10". Thus as seen in FIG. 4, flrst membrane 21 has a radius r2 and has its peripheral side edge region sealinaly engaged to the upper surface 13 of substrate 10". Second membrane 22 has a radius rl which is smaller than the radius of first membrane 21 and has its side edge region sealingly engaged to the upper surface 13 of substrate 10" in the region immediately adjacent to the opening 12 thereof. Second membrane 22 extends downwardly in a manner such that it passes through opening 12 to obtain a spaced, opposed relationship with repsect to first ~embrane 21 as clearly shown in FIG. 4.
The particular construction of the embodiment of the invention illustrated in FIG. 4 is advantageous in that by having the peripheral side edge regions o~ both membranes sealingly en~age the insulator substrate on the same side thereof, any stray capacitance which might exist between the edge regions $ 6 .
of membranes 21 and 22 which would otherwise adversely affect the capacitive measurements is maintained as low as possible.
Thus, in the case of each of the illustrated embodi-ments of the present invention, the capacitance existin~ between the opposed membranes 21,22 of capsule 20 is measured such, for example, as by leads 27 which are coupled to suitable instru-mentation known in the art. Thus, as the distance between membranes 21,22, designated d(p) in FIG. 4, decreases in response to an increase in pressure, the capacitance C will increase in a substantially linear mànner. Of course, as the inter-membrane distance increases as a result in pressure reduction, the capaci-tance C will diminish in the same manner.
Obviously, numberous modiEications and variations of the present invention are possible in the light of the above teachings. Accordinqly, it is understood that within the scope of the appended clafms the invention may be practiced otherwise than is described herein.
~; - 7 -
Thus, it is seen that according to the present invention, an extremely simple yet accurate and reliable capsule apparatus is provided whereby changes in pressure can be directly obtained by measuring the capacitance between the pair of opposed membranes 21,22 having the insulative substrate 10 interposed therebetween ;- _ 5 _ to electrically isolate the memhranes from each other. As mentioned above, the requirement of a separate capacitor component is obviated by the present invention thereby significantly reducing the cost and complexity of the device.
Referring to FIG. 3, the insulator substrate, designated 10', comprises a rin~-shaped annular member defining a circular opening 12 therewithin. First and second memhranes 21,22 have their peripheral side edge regions sealingly engaged to the upper and lower surfaces 13,14, respectively of substrate 10' at the region thereof adjacent to the opening 12. Thus, in this embodi-ment, a single evacuated space 23' is defined between first and second membranes 21,22.
Referring to FIG. 4, another embodiment of the capsule 20 of the present invention is illustrated wherein the insulator substrate 10" is also formed having a ring-shiped or annular configuration. However, in this case, the peripheral side edge regions of membranes 21,22 are sealingly engaged to the same side 13 of substrate 10". Thus as seen in FIG. 4, flrst membrane 21 has a radius r2 and has its peripheral side edge region sealinaly engaged to the upper surface 13 of substrate 10". Second membrane 22 has a radius rl which is smaller than the radius of first membrane 21 and has its side edge region sealingly engaged to the upper surface 13 of substrate 10" in the region immediately adjacent to the opening 12 thereof. Second membrane 22 extends downwardly in a manner such that it passes through opening 12 to obtain a spaced, opposed relationship with repsect to first ~embrane 21 as clearly shown in FIG. 4.
The particular construction of the embodiment of the invention illustrated in FIG. 4 is advantageous in that by having the peripheral side edge regions o~ both membranes sealingly en~age the insulator substrate on the same side thereof, any stray capacitance which might exist between the edge regions $ 6 .
of membranes 21 and 22 which would otherwise adversely affect the capacitive measurements is maintained as low as possible.
Thus, in the case of each of the illustrated embodi-ments of the present invention, the capacitance existin~ between the opposed membranes 21,22 of capsule 20 is measured such, for example, as by leads 27 which are coupled to suitable instru-mentation known in the art. Thus, as the distance between membranes 21,22, designated d(p) in FIG. 4, decreases in response to an increase in pressure, the capacitance C will increase in a substantially linear mànner. Of course, as the inter-membrane distance increases as a result in pressure reduction, the capaci-tance C will diminish in the same manner.
Obviously, numberous modiEications and variations of the present invention are possible in the light of the above teachings. Accordinqly, it is understood that within the scope of the appended clafms the invention may be practiced otherwise than is described herein.
~; - 7 -
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS;
1. An aneroid capsule apparatus for use in a pressure gauge comprising: a rigid substrate formed of electrically insulative material; a first self-supporting membrane formed of electrically conductive material having a peripherally extending side edge region sealingly engaged to said substrate; a second self-supporting membrane formed of electrically conductive ma-terial extending substantially parallel to and at a distance from said first membrane, said second membrane having a peripherally extending side edge region sealingly engaged to said substrate in electrically isolated relation to said first membrane, defining a sealed interior space between said first and second membrane which is partially evacuated, said first and second membranes having an electrical capacitance created between them and a pair of conductor means, each electrically communicating with a respective one of said electrically conductive membranes in a manner such that it does not extend within said sealed interior space, whereby changes in said capacitance between said membranes resulting from changes in pressure can be measured.
2. Apparatus as recited in claim 1 wherein said in-sulator substrate has a portion which extends outwardly beyond the peripheral side edge regions of said membranes and said out-wardly extending portion includes means for mounting said apparatus to other structure provided thereon.
3. Apparatus as recited in claim 1 wherein said in-sulator substrate comprises a substantially planar member having first and second opposite side surfaces to which the peripheral edge regions of said first and second membranes are respectively sealingly engaged.
4. Apparatus as recited in claim 3 wherein said insulator substrate extends through said sealed interior space to define a pair of sealed sub spaces.
5. Apparatus as recited in claim 1 wherein said insulator substrate comprises a ring-shaped annular member defining an opening therein and having first and second opposite side surfaces.
6. Apparatus as recited in claim 5 wherein the peri-pheral edge regions of said first and second membranes are sealingly engaged to said first and second side surfaces of said substrate, respectively, so that the opening defined in said substrate is located in the sealed interior space defined by said membranes.
7. Apparatus as recited in claim 6 wherein said first membrane has a first diameter and said second membrane has a second diameter which is smaller than the first diameter and wherein the peripheral edge regions of said membranes are sealing-ly engaged to the same side of said substrate whereby stray capacitance is diminished.
8. Apparatus as recited in claim 7 wherein the peripheral edge region of said second membrane is sealingly engaged to the edge region of the opening defined in said sub-strate.
9. Apparatus as recited in claim 8 wherein said second membrane extends through said opening.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000316733A CA1116428A (en) | 1978-11-23 | 1978-11-23 | Pressure gauge |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000316733A CA1116428A (en) | 1978-11-23 | 1978-11-23 | Pressure gauge |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116428A true CA1116428A (en) | 1982-01-19 |
Family
ID=4113000
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000316733A Expired CA1116428A (en) | 1978-11-23 | 1978-11-23 | Pressure gauge |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1116428A (en) |
-
1978
- 1978-11-23 CA CA000316733A patent/CA1116428A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |