CA1164240A - Capacitive pressure transducer with isolated sensing diaphragm - Google Patents
Capacitive pressure transducer with isolated sensing diaphragmInfo
- Publication number
- CA1164240A CA1164240A CA000387283A CA387283A CA1164240A CA 1164240 A CA1164240 A CA 1164240A CA 000387283 A CA000387283 A CA 000387283A CA 387283 A CA387283 A CA 387283A CA 1164240 A CA1164240 A CA 1164240A
- Authority
- CA
- Canada
- Prior art keywords
- diaphragm
- isolator
- sensor housing
- housing
- pressure transducer
- 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
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L13/00—Devices or apparatus for measuring differences of two or more fluid pressure values
- G01L13/02—Devices or apparatus for measuring differences of two or more fluid pressure values using elastically-deformable members or pistons as sensing elements
- G01L13/025—Devices or apparatus for measuring differences of two or more fluid pressure values using elastically-deformable members or pistons as sensing elements using diaphragms
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
- G01L9/0072—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance
Abstract
CAPACITIVE PRESSURE TRANSDUCER WITH
ISOLATED SENSING DIAPHRAGM
ABSTRACT OF THE DISCLOSURE
A capacitance transducer has a central chamber with a conductive diaphragm disposed therein to separate the chamber into at least two portions, at least one portion having an electrical conductor disposed thereon to form in combination with the diaphragm at least one variable sensor capacitor, and wherein at least one portion of the chamber is coupled by a passageway to communicate with an isolator having an isolator chamber and an isolator diaphragm which in combination with the conductive diaphragm enclose a substantially incompressible fluid such that when pressure is applied to an exposed side of the isolation diaphragm, the conductive diaphragm is urged to deflect and thus change the sensor capacitance. Configuration of the isolators, spaced from the sensor capacitors, and other factors disclosed herein, eliminate unwanted mechanical and thermal stresses thereby improving the capacitive sensors' response to pressure.
ISOLATED SENSING DIAPHRAGM
ABSTRACT OF THE DISCLOSURE
A capacitance transducer has a central chamber with a conductive diaphragm disposed therein to separate the chamber into at least two portions, at least one portion having an electrical conductor disposed thereon to form in combination with the diaphragm at least one variable sensor capacitor, and wherein at least one portion of the chamber is coupled by a passageway to communicate with an isolator having an isolator chamber and an isolator diaphragm which in combination with the conductive diaphragm enclose a substantially incompressible fluid such that when pressure is applied to an exposed side of the isolation diaphragm, the conductive diaphragm is urged to deflect and thus change the sensor capacitance. Configuration of the isolators, spaced from the sensor capacitors, and other factors disclosed herein, eliminate unwanted mechanical and thermal stresses thereby improving the capacitive sensors' response to pressure.
Description
2~0 CAPACITIVE PRESSURE TRANSDUCER WITII ISOLATED SENSING DIAP}IRAGM
BACKGROUND OF TIE INV~NTION
1. Fiel(l of the Invention The present invention relates to isolator arrangements for capacitive pressure sensors and to improved diaphragm mounting structurcs .
2. Prior Art U.S. Patent No. 3~618~390J owned by the same assignee as the present invention teaches the use of a sensing diaphragm which bottoms out on excessive pressure to protect the isolating diaphragms. This invention provided great impetus to capacitance pressure measurement techniques, as manifested by substantial commercial exploitation 2nd success. The present invention as taught herein may be used in cooperation with the structure claimed in U.S. Patent No. 3,618,390.
SU~RY OF THE INVENTION
The present invention includes the use of a capacitance type pressure sensor having a diaphragm disposed in a central chamber and havillg isolators so that the process fluid or other pressure is applied to the isolator and the pressure is communicated to the sensor by a substantially incompressible fluid via passageway means to the central chamber. The diaphragm is then urged by the incompressible fluid to move to a position which along with an electrically cond~uctive surface disposed on an internal surface of a portion of the central chamber forms a variable capacitor, which when driven by a suitable circuit produces an electrical signal responsive to pressure.
The invention envisions remote isolators, electrical iso-lation of the sensor from the isolators, and improved sensor mounting, material selection and configuration to reduce the effects of static line pressure and temperature. Such deleterious effects are substantially reduced, resulting in an improved capacitive signal wllich is representative of pressure.
.. .. _, .... .. .... . .... . . . . .. .
' , .
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view of a pressure transducer made in accordance wi~h the instant invention.
Fig. 2 is a sectional view of the sensor housing of anotller embodiment of the pressure transducer sensor housing.
Fig 3. is a graph showing the results of testing a transducer in accordance with an embodiment of the invention showing percent error v. differential pressure for five different calibrations, with different static line pressures on the transducer.
Fig. 4 is a graphic representation of the results of testing a transducer of the invention showing output deviation in percent v. differential line pressure to show temperature effect ~uncompensated) for several calibrations.
Figs. 5a and 5b are illustrative cross sectional representations showing the effect of increasing static line pressure on a capacitive sensing cell such as that shown in Figs. 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
... _ . . . .....
A transducer which preferably is used for differential pressure, gauge pressure, flowJ level or other such pressure measurement is shown generally at 10. The transducer includes a transducer housin~ or frame 12 which supports a sensor housing 14 and a pair of isolator housings 16a and 16b. It is 25 enuisioned that housings 14, 16a and 16b may be included in or spaced from housing 12. The pressures to be sensed are represented by arrows 18 and 20 at the transducer input ports. Pressures 18 and 20 act on isolator diaphragms 22 and 2~, respectively. Diaphragms 22 and 24 preferably are very flexible and are formed in a conventional manner. The corrugations 26 of diaphragms 22 and 24 represent a preferred isolator diaphragm construction having a plurality of convolutions, as desired. Chambers 27 and 29 are ,~ :
-4~
dcfincd by di.lphrag~l)s 22 and 24 iTl cooperation with the respective housings 16a and 16b. Chambers 27 and 29 are coupled ~o passage-ways 2S and 30, whic}l preferably are formed by stainless steel tubing, but may be formed from otller suitable materials.
Sensor housing 14 is preferably machincd and formed from a metal sucll as stainless steel, preferably an austenitic stain-less steel such as 304 is used. Generally~ housillg 14 is formed from two portions 32 and 34 which preferably are substantially equal in size and when assembled are generally divided by a sensor diaphragm 36 which is held at its edges and will elastically deflect under differential pressures and which typically is subjected to a desired radial tension. A central cone shaped cavity 38 with bores 42 and 44 is formed in portion 32 and, similarly a central cone shaped cavity 46 with bores 48 and 50 is formed in portion 34. Conduits 52 and 54 are formed in portions 32 and 34 to communicate with passage-ways 28 and 30, respectively. The interior openings of the conduits 52 and 54 form continuations of the passageways 28 and 30 to com-municate with a cllamber 53 defined in portion 32 by diaphragm 36 and the central section of material 60a in portion 32 and a second chamber 55 defined .in portion 34 by diaphragm 36 and the central section of material 60b in portion 34. An electrical conductor 56 is inserted Ihrough bore 42 to chamber 38 and, similarly, a conductor 58 is inserted througll bore 48 to chamber 46. Conductors Sfi and 58 may be metal tubes to aid in filling the sensor chambers with a non-compressible fluid.
The electrically conductive portions of the housing 14 are electrically insulated from the metal tubes forming passage-ways 28 ancl 30 and from conductors 56 and 58. An insul~tive non-porous material 60a and 60b such as glass or ceramic, is filled into cavities 38 and 46 and bores 42 and 48 and is bonded to housing porti.ons 32 and 34 along a surface forming an angle ~
with respect to the plane formed by the joining of portions 32 and 34. The central section of material 60a and 60b and the central area of housing portions 32 and 34, as well as inner ends of .... , .. __.. ~ . ;
1~4~9L[3 conductors 56 and 5~ are ~hen contoured or recessed by grinding or machining, preferably to provide a suitable stop surface for sensor diaphragm 36 when the diaphragm 36 deflects under an over-range pressure applied to the isolator diaphragms. Conduits 52, 54 IDay be a single cylinder as shown , or a plurality of small cylinders in accord with the teaching of U.S. Patent No. 3,61~7,390 to provicle diaphragm su~port in an overpressure condition.
A suitable electrically conductive material is then de-posited in a layer on the inner surface of material 60a and 60b in each housillg portion as at 61 and 63. The layers face opposite sides of the sensor diaphragm 36 and are electrically coupled to conductors 56 and 58, respectively. Sensor diaphragm 36 prefer-ably is formed from a suitable electrically conductive material and is fi~ed into position between housing portions 32 and 3~
and layers 61 and 63 by a continuous bead weld 62 thus forming a common plate for material 61 and 63, hence forming two ca-pacitors Cl and C2. A suitable conductor 64 is then coupled to sensor housing 14 l~hich is at the same electrical potential as diaphragm 36. Sensor diaphragm 36 can also be formed from a non-conductive material and have a conductive portion disposed in or on the diaphragm to form such common plate for a variable sensor capacitor. A suitable conductor 64 is then coupled to such conducti~e portion. Bolts 70 may then be added to take up the pressure forces on sensor housing 14.
A suitable, substantially incompressible fluid, such as silicone oil, is then filled into each side of the transducer assenlbly throug]l conductors 56 and 58 to ~he sensor diaphragm chamber formed in housing portion 32 by diaphragm 36, and to isolating chamber 27, and similarly to the sensor cham~er in housill~ portion 3~, and isolating chamber 29. When such spaces are filled, conductors 56 and 58 are pinched off at their outer ends and suitable leadwires are attached thereto.
The action of pressure on isolator diaphragms 22 and 24, the substantially incompressible fluid in chambers 27 and 297 . . .
. . ~
' 24~) passageways 28 and 30, and on sensing diaphragm 36 is fully explained, for example, in United States Patent 3,618,390.
The invention of the sensing diaphragm 36 bottoming out in all ovcrpressure condition as taught in U.S. Patent 3,618,390 or the isolating diaphragm 22 or 24 boLtoming out in an overpressure condition may, as desired, be used with the present invention.
The physical location of isolator diap}lragms 22 and 24 spaced from sensor diaphragm 36 is show]l somewhat schematically, as the location of isolator diaphragms 22 and 24 is not critical, pro-viding that such diaphragms are located so as not to apply undesired mechanical stress, other than the pressure through the incom-pressible fluid, to sensor housing 14. ~lile sensor housing 14 preferably is fixedly mounted :in housing 12 it is not requi.red that it be rigidly mounted as by welding. As shown, it is re-tained by flc~ible straps 71, which are formed from an electrical insulative ~naterial to electrically isolate the sensor housing 14 from transducer housing 12 and to support sensor housing 14.
~ith chambers 27, 29, passageways 28 and 30 ~including opcnings in conduits 52 and 54) and the chambers between layers 61 and 63 and diaphragm 36 filled with incompressible fluid, differ-entials between pressures represented by arrows 18 and 20 will cause diaphragm 36 to deflect proportional to pressure differ-ential ancl its capacitance relative to layers 61 and 63 changes.
Another embodiment of the invention is shown in Fig. 2.
In this embodiment the sensor housing 14A is somewhat wider than tlle embodiment of Fig. 1. I~lile the numbering corresponds to Fig. 1, (with a capital letter forming a part of ~he alphanumeric designations thereof) it is observed that with the increased width of sensor hous.ing 14A, bores 44~ and 50~ are somewhat deeper in Fig. 2 than bores 44 and 50, and material 60A and 60B, has been filled to include a portion of such bores. An angle 0 is the . ~ . ~ -~1ti42~
included angle from the plane of diaphragm 36A at its rest position to the conical surface forming the rccess in the respective housing portion in wllicll material 60~ and 60B is filled. lhis angle determines the effective depth of the material 60A,60B (or 60a, 60b in tlle first torm of the invelltioll) whicll backs the capacitor plates 61A and 63A (or 61 and 63). Although an angle ~ of approxi-mately 45 is preferred for the embodiments of Fi~. 1 and 2, it has been found that angles from 25 to 70 have resulted in improved stability and th~ls improved perormance over known constructions which comprise, for example, a non-compressive bond between the insulating material and metal. ~le angle also can be measured with respect to the central axis of the sensor housing which is perpendicular to the plane of diaphragm 36A (or 36) when it is at rest.
One significant advantage of the present invention is improvement of the static pressure effect on the pressure span of the transducer. In prior art embodiments, the effect of static prcssure on span error has been found to be approximately a one percent (lYo) challge in output across the instrument span per one thousand (1000) pounds per square inch (PSI) change of static pressure. In such known transducers, the pressure on the outside of the sensor housillg, caused by the pressure being sensed acting Oll the isolating diaphragms, and pressure from the^inside of the sensor chamber caused by the pressure being sensed on tlle incom-pressible fluid resulted in sensor housing deformation outwardlyin a known manner, as per Poisson's ratio.
~ urther, in Xnown methods of manufacturing such capaci-tive transducers ! ~he insulating material, upon which the con-ductive material is deposited to form the second plate of each of ~0 the variable capacitors, has been relatlvely thin in comparison to the .insulative material thickness in the central cavlty of the `' :
.. ,...... ..... ~ .. , sensor housing as disclosed herein. ~en the insulative material is thin or when thc insulating material to metal inter-~ace is son1ewhat parallel to the rest aYis oi' the diaphragm (perpendicular to plal1e of tl1e diapl1ragm), the insulating matcrial-metal inter-.lCeS (bo11d) 65a, 65~, 65A, 65B are thel1 subjected to a shearforce w]1ich may cause the bond to weaken or fracture. 1Yhen pressurc is applied to a sensor having a fractured bond, such pressure callses the insulating material to move away rom the diaphragm. The movement of ~he insulator material causes an undesirable change in capacitance not representative of the sensed pressure, which adds to the error effect caused by the static line pressure. ~Yhen the sensor is formed in accordance Wit}1 the present disclosure, bonds 65a, 65b,'65A, 65B are substan~ially in compression an~, consequently, much less vulnerable to such lS fracture.
By remov:ing the isolators from the side of the sensor housi11g, the capacitor plate spacing on both sides of the dia-phragm 36 increases witl1 increasing static line pressure applied at lS, 20 due to slight outward motion of the sensor portions with respect to the sensor diaphragm. This static line pressure increase also causes portions 32 and 34 tô warp slightly about their respective neutral axes (shown in Figs. 2 and 5 at X-X) as the th~O housi11g portions tend to contract adjacent the diaphragm (as shown by arrows 70A in the Figs. 2 ~ 5B). (The ins~lation material is not specifically shown in F:igs. SA or 5B since these Figures are illustrative only and apply to the configurations of Figs. l and 2.) Such warping is perhaps best explained by reference to Fig. 5A which shows portions 32 and 34 at rest and in Fig. 5B whicl1 shows an exaggerated warp condition (for emphasis) as caused by increasing static line pressure. As the static line pressure is increased the capacitance spacing (d) of Fig. 5A be-tween the diaphragm 36 and capacitor plates 61 and 63 increases to d' (as shown in Fig. 5B) and such spacing change is not repre-sentative of the applied dii'ferential pressure. In accordance ~ ,. ~ .. ,.,.. ~
q) with the present invention 7 the change in capacitance caused by such warping is substanticllly compensatcd for by the decrease in diaphragm radial tension caused by the contraction adjacent the diaphragm. Radial tension or prestress applied to the diaphragm at time of construction along with suitable dimensions and materi-als results in tlle elastic stiffnesc of the diaphragm decreasing with increasing static pressure. Preferably the diaphragm material is high strength steel having good elastic characteristics. The compensation advantage is present at all static line pressures, but more fully realized at static line pressures above 500 psi.
The following equations further explain the static line pressure compensation according to a preferred embodiment of the instant invention having a first capacitor Cl and a second capaci-tor C2 as described hereill:
C~l+CL Xo x ~
l~ere 0 = the output signal from the differential pressure capacitance cell.
CH = the capacitance`of the greater of Cl or C2.
CL = the capacitance of the 1 `C
Xp = diaphragm deflection with differential pressure.
Xo = capacitance spacing at zero (0) static line gauge pressure.
Xo' = capacitance spacing ac elevated static line pressure.
... .
, o = diaphragm stretch at time of construction (initial prestretch).
' = diaphragm stretch at elevated static line pressure.
Simplifying:
0 ~J~
l~len the trallsdUCer i5 formed in accordance with the present in-vention as tlle static line pressure increases, the capacitance spacing Xo increases to Xo' and the diaphragm stretch (~O) de-creases to ~ '. By holding the product of Xo-~ substantially equal to Xo'-oO' hence, substantially equal to a constant, the diaphra~l deflcctio1l (Xp) is responsive to the differential pressure applied thereto and the output (0) is thus independent of static line pressure.
A transducer, made in accordance with the embodiments of Fig. 1 and Fig. 2, but not having an angle e between 25 and 7a rather having a cylindrical, metal-insula~ing material interface bond;
that is~ the bond interface was first generally perpendicular ~ = 90) from diaphragm 36, then generally parallel (~ = 0) from diaphragm 36 generally as shown in U.S; Patent ~o. 3,618,39Q, was tested under actual loading conditions. This early form of the invention did not then~include the compressive bond taught herein, but rather had the prior art shear bond.
The improved bond is helpful as taught to avoid bond fracture and ir. is belielred fro~ ~na~y~ation and evaluation that such fracture did not occur and, therefore the nature of the bond did not affect test results. In the embodiment ~ested, the other princip]es of the invention we~e followedl_sl~ch as sel)aratillg thc isolutor 16a, 16~ fI`OIIl sensor housillg 14 and compen-sating for sensor llousing 14 warp with a suitable sensor diaphragm 36 prestress. Sensor dlaphragm 36 was ..~ mils th;ck an~ ay ~.
:
' proximately 1.12 inch in diameter and had approximately 105,000 PSI in prestress applied (though prestress from 50,000 to 200,000 PSI may be acceptable) and was formed from NiSpan C
~trademark); insulative material 60a, 60b, 60A, 60B was Owens 5 0120 ~trademark) glass; and, sensor housing 14 was NiSpan C
(trademark) material approximately 1.250 inches in diameter.
Capacitance spacing ~Xo) in the center was approximately .0075 inches. Isolators 16a, 16b were formed from stainless steel (304SST) and were approximately 3 inches in diameter and were coupled to chambers 53, 55 by passageways 28, 30 formed from 1/16 inch O.D. stainless steel tubing. The results of such testing are shown in Fig. 3~ As shown, all test points deviations due to static line pressure effect from zero (0) PSIG to two thousand (2000) PSIG are less than .2% across the differential pressure span of 0 to 240 inches of water. The curves of Fig. 3 show a very small mechanical hysteresis. Such mechanical hysteresis is not uncommon and depends not only on the instantaneous value of stress as caused by differential pressure and static line pressure but also on the previous history of such stress.
Yet a further improvement is attained by the present invention, as the zero stability of the transducer, which in known transducers varies with both temperature and static pressure, -s improved because the isolator housings are not in direct physical contact with the sensor housing. Only the tubes orming passageways 28 and 30 are in direct contact with sensor housing 14 and these tubes yield to accommodate loads or changes due to temperature on the isolators without stressing the sensor housing 14.
A test also was conducted to demonstrate the improved uncompensated temperature effect with respect to the stability of the output capacitance signal of the present invention of the embodiment described above; such results are shown in Fig. 4. The "uncompensated"
efect is the error present before any compensation of an electrical signal is applied. Electrical signal compensation ' :
~1~42~0 is commonly used to reduce errors f~lrther, but it is highly adviall-tageous to provide a structure having a low wlcompensated error.
Each curve of Fig. 4 represents a separate calibration. Several sucll calibrations were accomplisllecl, seven of which are shown on Fig. 4, one at 100l, then again at 100F, then at 200~, tllen 100 F, tllen 0 I, thell 100F, again 200F, and finally at 100 F. The curves show that the configuration resul-ted in excellent stability and in a very low thermal hysteresis as the capacitance deviation at 100 F for three calibrations at tllat temperature was less tllan ~ .18%. Thermal hysteresis refers to the difference in calibration results at a specific tempcrature after coming to that calibration temperature from higher and lower tem?eratures respectively.
Many embodiments formed of different materials and having different dimensions have been successfully tested; in successful tests, the sensor diaphragm 36 was formed from llavar ~ steel of 1lamiltoll Industries (or Elgiloy ~ alloy of Elgiloy Co.)~ insulative material 60 was alkali lead glass;, specifically Corning 1990 glass and the sensor housing 14 was austenitic s-tainless steel.
One further advantage of the present invention is that since the isolator diaphragms are 110 longer an integral part of the sensor housing 1~, the size of the isolator diaphragms may be increased relative to the sensoF housing. This increase in size is important in some instances to reduce the effects of temperature and other factors 011 overall transducer performance.
Further, sensor housing 14 preferably is electrically isolated from transducer housing 12 resulting in a simplification of tlle transducer circuitry when electrical isolation is desi~ed which is often the case for industrial pressure measurements.
I~lile tlle invention has been described using a variable ca-pacitance sensor, those skilled in tlle art understand that a variable impedance, that is a variable impedance variable reactance sensor, c~n he used ~-ith t~e invention as described herein~ .
In su~mnary, the several listed advantages as welI as those apparent to those skilled in the art are realized from $1ie improYemCntS of tllc~ present irlvelltioll.
.,.
_ . . . ... . .
BACKGROUND OF TIE INV~NTION
1. Fiel(l of the Invention The present invention relates to isolator arrangements for capacitive pressure sensors and to improved diaphragm mounting structurcs .
2. Prior Art U.S. Patent No. 3~618~390J owned by the same assignee as the present invention teaches the use of a sensing diaphragm which bottoms out on excessive pressure to protect the isolating diaphragms. This invention provided great impetus to capacitance pressure measurement techniques, as manifested by substantial commercial exploitation 2nd success. The present invention as taught herein may be used in cooperation with the structure claimed in U.S. Patent No. 3,618,390.
SU~RY OF THE INVENTION
The present invention includes the use of a capacitance type pressure sensor having a diaphragm disposed in a central chamber and havillg isolators so that the process fluid or other pressure is applied to the isolator and the pressure is communicated to the sensor by a substantially incompressible fluid via passageway means to the central chamber. The diaphragm is then urged by the incompressible fluid to move to a position which along with an electrically cond~uctive surface disposed on an internal surface of a portion of the central chamber forms a variable capacitor, which when driven by a suitable circuit produces an electrical signal responsive to pressure.
The invention envisions remote isolators, electrical iso-lation of the sensor from the isolators, and improved sensor mounting, material selection and configuration to reduce the effects of static line pressure and temperature. Such deleterious effects are substantially reduced, resulting in an improved capacitive signal wllich is representative of pressure.
.. .. _, .... .. .... . .... . . . . .. .
' , .
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view of a pressure transducer made in accordance wi~h the instant invention.
Fig. 2 is a sectional view of the sensor housing of anotller embodiment of the pressure transducer sensor housing.
Fig 3. is a graph showing the results of testing a transducer in accordance with an embodiment of the invention showing percent error v. differential pressure for five different calibrations, with different static line pressures on the transducer.
Fig. 4 is a graphic representation of the results of testing a transducer of the invention showing output deviation in percent v. differential line pressure to show temperature effect ~uncompensated) for several calibrations.
Figs. 5a and 5b are illustrative cross sectional representations showing the effect of increasing static line pressure on a capacitive sensing cell such as that shown in Figs. 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
... _ . . . .....
A transducer which preferably is used for differential pressure, gauge pressure, flowJ level or other such pressure measurement is shown generally at 10. The transducer includes a transducer housin~ or frame 12 which supports a sensor housing 14 and a pair of isolator housings 16a and 16b. It is 25 enuisioned that housings 14, 16a and 16b may be included in or spaced from housing 12. The pressures to be sensed are represented by arrows 18 and 20 at the transducer input ports. Pressures 18 and 20 act on isolator diaphragms 22 and 2~, respectively. Diaphragms 22 and 24 preferably are very flexible and are formed in a conventional manner. The corrugations 26 of diaphragms 22 and 24 represent a preferred isolator diaphragm construction having a plurality of convolutions, as desired. Chambers 27 and 29 are ,~ :
-4~
dcfincd by di.lphrag~l)s 22 and 24 iTl cooperation with the respective housings 16a and 16b. Chambers 27 and 29 are coupled ~o passage-ways 2S and 30, whic}l preferably are formed by stainless steel tubing, but may be formed from otller suitable materials.
Sensor housing 14 is preferably machincd and formed from a metal sucll as stainless steel, preferably an austenitic stain-less steel such as 304 is used. Generally~ housillg 14 is formed from two portions 32 and 34 which preferably are substantially equal in size and when assembled are generally divided by a sensor diaphragm 36 which is held at its edges and will elastically deflect under differential pressures and which typically is subjected to a desired radial tension. A central cone shaped cavity 38 with bores 42 and 44 is formed in portion 32 and, similarly a central cone shaped cavity 46 with bores 48 and 50 is formed in portion 34. Conduits 52 and 54 are formed in portions 32 and 34 to communicate with passage-ways 28 and 30, respectively. The interior openings of the conduits 52 and 54 form continuations of the passageways 28 and 30 to com-municate with a cllamber 53 defined in portion 32 by diaphragm 36 and the central section of material 60a in portion 32 and a second chamber 55 defined .in portion 34 by diaphragm 36 and the central section of material 60b in portion 34. An electrical conductor 56 is inserted Ihrough bore 42 to chamber 38 and, similarly, a conductor 58 is inserted througll bore 48 to chamber 46. Conductors Sfi and 58 may be metal tubes to aid in filling the sensor chambers with a non-compressible fluid.
The electrically conductive portions of the housing 14 are electrically insulated from the metal tubes forming passage-ways 28 ancl 30 and from conductors 56 and 58. An insul~tive non-porous material 60a and 60b such as glass or ceramic, is filled into cavities 38 and 46 and bores 42 and 48 and is bonded to housing porti.ons 32 and 34 along a surface forming an angle ~
with respect to the plane formed by the joining of portions 32 and 34. The central section of material 60a and 60b and the central area of housing portions 32 and 34, as well as inner ends of .... , .. __.. ~ . ;
1~4~9L[3 conductors 56 and 5~ are ~hen contoured or recessed by grinding or machining, preferably to provide a suitable stop surface for sensor diaphragm 36 when the diaphragm 36 deflects under an over-range pressure applied to the isolator diaphragms. Conduits 52, 54 IDay be a single cylinder as shown , or a plurality of small cylinders in accord with the teaching of U.S. Patent No. 3,61~7,390 to provicle diaphragm su~port in an overpressure condition.
A suitable electrically conductive material is then de-posited in a layer on the inner surface of material 60a and 60b in each housillg portion as at 61 and 63. The layers face opposite sides of the sensor diaphragm 36 and are electrically coupled to conductors 56 and 58, respectively. Sensor diaphragm 36 prefer-ably is formed from a suitable electrically conductive material and is fi~ed into position between housing portions 32 and 3~
and layers 61 and 63 by a continuous bead weld 62 thus forming a common plate for material 61 and 63, hence forming two ca-pacitors Cl and C2. A suitable conductor 64 is then coupled to sensor housing 14 l~hich is at the same electrical potential as diaphragm 36. Sensor diaphragm 36 can also be formed from a non-conductive material and have a conductive portion disposed in or on the diaphragm to form such common plate for a variable sensor capacitor. A suitable conductor 64 is then coupled to such conducti~e portion. Bolts 70 may then be added to take up the pressure forces on sensor housing 14.
A suitable, substantially incompressible fluid, such as silicone oil, is then filled into each side of the transducer assenlbly throug]l conductors 56 and 58 to ~he sensor diaphragm chamber formed in housing portion 32 by diaphragm 36, and to isolating chamber 27, and similarly to the sensor cham~er in housill~ portion 3~, and isolating chamber 29. When such spaces are filled, conductors 56 and 58 are pinched off at their outer ends and suitable leadwires are attached thereto.
The action of pressure on isolator diaphragms 22 and 24, the substantially incompressible fluid in chambers 27 and 297 . . .
. . ~
' 24~) passageways 28 and 30, and on sensing diaphragm 36 is fully explained, for example, in United States Patent 3,618,390.
The invention of the sensing diaphragm 36 bottoming out in all ovcrpressure condition as taught in U.S. Patent 3,618,390 or the isolating diaphragm 22 or 24 boLtoming out in an overpressure condition may, as desired, be used with the present invention.
The physical location of isolator diap}lragms 22 and 24 spaced from sensor diaphragm 36 is show]l somewhat schematically, as the location of isolator diaphragms 22 and 24 is not critical, pro-viding that such diaphragms are located so as not to apply undesired mechanical stress, other than the pressure through the incom-pressible fluid, to sensor housing 14. ~lile sensor housing 14 preferably is fixedly mounted :in housing 12 it is not requi.red that it be rigidly mounted as by welding. As shown, it is re-tained by flc~ible straps 71, which are formed from an electrical insulative ~naterial to electrically isolate the sensor housing 14 from transducer housing 12 and to support sensor housing 14.
~ith chambers 27, 29, passageways 28 and 30 ~including opcnings in conduits 52 and 54) and the chambers between layers 61 and 63 and diaphragm 36 filled with incompressible fluid, differ-entials between pressures represented by arrows 18 and 20 will cause diaphragm 36 to deflect proportional to pressure differ-ential ancl its capacitance relative to layers 61 and 63 changes.
Another embodiment of the invention is shown in Fig. 2.
In this embodiment the sensor housing 14A is somewhat wider than tlle embodiment of Fig. 1. I~lile the numbering corresponds to Fig. 1, (with a capital letter forming a part of ~he alphanumeric designations thereof) it is observed that with the increased width of sensor hous.ing 14A, bores 44~ and 50~ are somewhat deeper in Fig. 2 than bores 44 and 50, and material 60A and 60B, has been filled to include a portion of such bores. An angle 0 is the . ~ . ~ -~1ti42~
included angle from the plane of diaphragm 36A at its rest position to the conical surface forming the rccess in the respective housing portion in wllicll material 60~ and 60B is filled. lhis angle determines the effective depth of the material 60A,60B (or 60a, 60b in tlle first torm of the invelltioll) whicll backs the capacitor plates 61A and 63A (or 61 and 63). Although an angle ~ of approxi-mately 45 is preferred for the embodiments of Fi~. 1 and 2, it has been found that angles from 25 to 70 have resulted in improved stability and th~ls improved perormance over known constructions which comprise, for example, a non-compressive bond between the insulating material and metal. ~le angle also can be measured with respect to the central axis of the sensor housing which is perpendicular to the plane of diaphragm 36A (or 36) when it is at rest.
One significant advantage of the present invention is improvement of the static pressure effect on the pressure span of the transducer. In prior art embodiments, the effect of static prcssure on span error has been found to be approximately a one percent (lYo) challge in output across the instrument span per one thousand (1000) pounds per square inch (PSI) change of static pressure. In such known transducers, the pressure on the outside of the sensor housillg, caused by the pressure being sensed acting Oll the isolating diaphragms, and pressure from the^inside of the sensor chamber caused by the pressure being sensed on tlle incom-pressible fluid resulted in sensor housing deformation outwardlyin a known manner, as per Poisson's ratio.
~ urther, in Xnown methods of manufacturing such capaci-tive transducers ! ~he insulating material, upon which the con-ductive material is deposited to form the second plate of each of ~0 the variable capacitors, has been relatlvely thin in comparison to the .insulative material thickness in the central cavlty of the `' :
.. ,...... ..... ~ .. , sensor housing as disclosed herein. ~en the insulative material is thin or when thc insulating material to metal inter-~ace is son1ewhat parallel to the rest aYis oi' the diaphragm (perpendicular to plal1e of tl1e diapl1ragm), the insulating matcrial-metal inter-.lCeS (bo11d) 65a, 65~, 65A, 65B are thel1 subjected to a shearforce w]1ich may cause the bond to weaken or fracture. 1Yhen pressurc is applied to a sensor having a fractured bond, such pressure callses the insulating material to move away rom the diaphragm. The movement of ~he insulator material causes an undesirable change in capacitance not representative of the sensed pressure, which adds to the error effect caused by the static line pressure. ~Yhen the sensor is formed in accordance Wit}1 the present disclosure, bonds 65a, 65b,'65A, 65B are substan~ially in compression an~, consequently, much less vulnerable to such lS fracture.
By remov:ing the isolators from the side of the sensor housi11g, the capacitor plate spacing on both sides of the dia-phragm 36 increases witl1 increasing static line pressure applied at lS, 20 due to slight outward motion of the sensor portions with respect to the sensor diaphragm. This static line pressure increase also causes portions 32 and 34 tô warp slightly about their respective neutral axes (shown in Figs. 2 and 5 at X-X) as the th~O housi11g portions tend to contract adjacent the diaphragm (as shown by arrows 70A in the Figs. 2 ~ 5B). (The ins~lation material is not specifically shown in F:igs. SA or 5B since these Figures are illustrative only and apply to the configurations of Figs. l and 2.) Such warping is perhaps best explained by reference to Fig. 5A which shows portions 32 and 34 at rest and in Fig. 5B whicl1 shows an exaggerated warp condition (for emphasis) as caused by increasing static line pressure. As the static line pressure is increased the capacitance spacing (d) of Fig. 5A be-tween the diaphragm 36 and capacitor plates 61 and 63 increases to d' (as shown in Fig. 5B) and such spacing change is not repre-sentative of the applied dii'ferential pressure. In accordance ~ ,. ~ .. ,.,.. ~
q) with the present invention 7 the change in capacitance caused by such warping is substanticllly compensatcd for by the decrease in diaphragm radial tension caused by the contraction adjacent the diaphragm. Radial tension or prestress applied to the diaphragm at time of construction along with suitable dimensions and materi-als results in tlle elastic stiffnesc of the diaphragm decreasing with increasing static pressure. Preferably the diaphragm material is high strength steel having good elastic characteristics. The compensation advantage is present at all static line pressures, but more fully realized at static line pressures above 500 psi.
The following equations further explain the static line pressure compensation according to a preferred embodiment of the instant invention having a first capacitor Cl and a second capaci-tor C2 as described hereill:
C~l+CL Xo x ~
l~ere 0 = the output signal from the differential pressure capacitance cell.
CH = the capacitance`of the greater of Cl or C2.
CL = the capacitance of the 1 `C
Xp = diaphragm deflection with differential pressure.
Xo = capacitance spacing at zero (0) static line gauge pressure.
Xo' = capacitance spacing ac elevated static line pressure.
... .
, o = diaphragm stretch at time of construction (initial prestretch).
' = diaphragm stretch at elevated static line pressure.
Simplifying:
0 ~J~
l~len the trallsdUCer i5 formed in accordance with the present in-vention as tlle static line pressure increases, the capacitance spacing Xo increases to Xo' and the diaphragm stretch (~O) de-creases to ~ '. By holding the product of Xo-~ substantially equal to Xo'-oO' hence, substantially equal to a constant, the diaphra~l deflcctio1l (Xp) is responsive to the differential pressure applied thereto and the output (0) is thus independent of static line pressure.
A transducer, made in accordance with the embodiments of Fig. 1 and Fig. 2, but not having an angle e between 25 and 7a rather having a cylindrical, metal-insula~ing material interface bond;
that is~ the bond interface was first generally perpendicular ~ = 90) from diaphragm 36, then generally parallel (~ = 0) from diaphragm 36 generally as shown in U.S; Patent ~o. 3,618,39Q, was tested under actual loading conditions. This early form of the invention did not then~include the compressive bond taught herein, but rather had the prior art shear bond.
The improved bond is helpful as taught to avoid bond fracture and ir. is belielred fro~ ~na~y~ation and evaluation that such fracture did not occur and, therefore the nature of the bond did not affect test results. In the embodiment ~ested, the other princip]es of the invention we~e followedl_sl~ch as sel)aratillg thc isolutor 16a, 16~ fI`OIIl sensor housillg 14 and compen-sating for sensor llousing 14 warp with a suitable sensor diaphragm 36 prestress. Sensor dlaphragm 36 was ..~ mils th;ck an~ ay ~.
:
' proximately 1.12 inch in diameter and had approximately 105,000 PSI in prestress applied (though prestress from 50,000 to 200,000 PSI may be acceptable) and was formed from NiSpan C
~trademark); insulative material 60a, 60b, 60A, 60B was Owens 5 0120 ~trademark) glass; and, sensor housing 14 was NiSpan C
(trademark) material approximately 1.250 inches in diameter.
Capacitance spacing ~Xo) in the center was approximately .0075 inches. Isolators 16a, 16b were formed from stainless steel (304SST) and were approximately 3 inches in diameter and were coupled to chambers 53, 55 by passageways 28, 30 formed from 1/16 inch O.D. stainless steel tubing. The results of such testing are shown in Fig. 3~ As shown, all test points deviations due to static line pressure effect from zero (0) PSIG to two thousand (2000) PSIG are less than .2% across the differential pressure span of 0 to 240 inches of water. The curves of Fig. 3 show a very small mechanical hysteresis. Such mechanical hysteresis is not uncommon and depends not only on the instantaneous value of stress as caused by differential pressure and static line pressure but also on the previous history of such stress.
Yet a further improvement is attained by the present invention, as the zero stability of the transducer, which in known transducers varies with both temperature and static pressure, -s improved because the isolator housings are not in direct physical contact with the sensor housing. Only the tubes orming passageways 28 and 30 are in direct contact with sensor housing 14 and these tubes yield to accommodate loads or changes due to temperature on the isolators without stressing the sensor housing 14.
A test also was conducted to demonstrate the improved uncompensated temperature effect with respect to the stability of the output capacitance signal of the present invention of the embodiment described above; such results are shown in Fig. 4. The "uncompensated"
efect is the error present before any compensation of an electrical signal is applied. Electrical signal compensation ' :
~1~42~0 is commonly used to reduce errors f~lrther, but it is highly adviall-tageous to provide a structure having a low wlcompensated error.
Each curve of Fig. 4 represents a separate calibration. Several sucll calibrations were accomplisllecl, seven of which are shown on Fig. 4, one at 100l, then again at 100F, then at 200~, tllen 100 F, tllen 0 I, thell 100F, again 200F, and finally at 100 F. The curves show that the configuration resul-ted in excellent stability and in a very low thermal hysteresis as the capacitance deviation at 100 F for three calibrations at tllat temperature was less tllan ~ .18%. Thermal hysteresis refers to the difference in calibration results at a specific tempcrature after coming to that calibration temperature from higher and lower tem?eratures respectively.
Many embodiments formed of different materials and having different dimensions have been successfully tested; in successful tests, the sensor diaphragm 36 was formed from llavar ~ steel of 1lamiltoll Industries (or Elgiloy ~ alloy of Elgiloy Co.)~ insulative material 60 was alkali lead glass;, specifically Corning 1990 glass and the sensor housing 14 was austenitic s-tainless steel.
One further advantage of the present invention is that since the isolator diaphragms are 110 longer an integral part of the sensor housing 1~, the size of the isolator diaphragms may be increased relative to the sensoF housing. This increase in size is important in some instances to reduce the effects of temperature and other factors 011 overall transducer performance.
Further, sensor housing 14 preferably is electrically isolated from transducer housing 12 resulting in a simplification of tlle transducer circuitry when electrical isolation is desi~ed which is often the case for industrial pressure measurements.
I~lile tlle invention has been described using a variable ca-pacitance sensor, those skilled in tlle art understand that a variable impedance, that is a variable impedance variable reactance sensor, c~n he used ~-ith t~e invention as described herein~ .
In su~mnary, the several listed advantages as welI as those apparent to those skilled in the art are realized from $1ie improYemCntS of tllc~ present irlvelltioll.
.,.
_ . . . ... . .
Claims (21)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. A capacitive pressure transducer including:
a transducer housing;
a sensor housing having a central cavity and being mounted relative to the transducer housing;
diaphragm means supported on said sensor housing and extending across the central cavity to thereby divide the central cavity into two central chambers, said diaphragm means being deflectable under pressure and at least a portion thereof being conductive to provide a first capacitor plate;
each of said central chambers having a conductive surface portion spaced from the diaphragm means for providing second plates of a pair of variable sensor capacitors, each formed with the diaphragm means comprising the first plate;
a pair of isolators, said isolators each having an isolator chamber and an isolator diaphragm disposed therein;
separate passageway means coupling each isolator chamber to a separate one of the central chambers;
means to permit applying separate pressures to the respective isolator diaphragms at a static line pressure, each isolator chamber, its associated passageway means and connected central chamber enclosing a substantially incompressible fluid, the diaphragm means deflecting and changing the capacitance of the variable sensor capacitors responsive to the differential between the static line pressures applied to the isolator diaphragms, and means for physically supporting the isolators in a position spaced from the sensor housing, the sensor housing and the diaphragm means being constructed to warp and to deflect to reduce error in capacitance indicated by the varible sensor capacitors as the diaphragm means deflects in response to the same differential in the static line pressures on the isolator diaphragms but at substantially different static pressure levels.
a transducer housing;
a sensor housing having a central cavity and being mounted relative to the transducer housing;
diaphragm means supported on said sensor housing and extending across the central cavity to thereby divide the central cavity into two central chambers, said diaphragm means being deflectable under pressure and at least a portion thereof being conductive to provide a first capacitor plate;
each of said central chambers having a conductive surface portion spaced from the diaphragm means for providing second plates of a pair of variable sensor capacitors, each formed with the diaphragm means comprising the first plate;
a pair of isolators, said isolators each having an isolator chamber and an isolator diaphragm disposed therein;
separate passageway means coupling each isolator chamber to a separate one of the central chambers;
means to permit applying separate pressures to the respective isolator diaphragms at a static line pressure, each isolator chamber, its associated passageway means and connected central chamber enclosing a substantially incompressible fluid, the diaphragm means deflecting and changing the capacitance of the variable sensor capacitors responsive to the differential between the static line pressures applied to the isolator diaphragms, and means for physically supporting the isolators in a position spaced from the sensor housing, the sensor housing and the diaphragm means being constructed to warp and to deflect to reduce error in capacitance indicated by the varible sensor capacitors as the diaphragm means deflects in response to the same differential in the static line pressures on the isolator diaphragms but at substantially different static pressure levels.
2. A capacitive pressure transducer according to Claim 1 wherein the diaphragm means is supported with respect to the sensor housing to provide an initial prestress on the diaphragm means.
3. A capacitive pressure transducer according to Claim 1 and means to support the isolators physically spaced from the sensor housing for isolation.
4. A capacitive pressure transducer according to Claim 1 wherein the diaphragm means is constructed of material that changes in stress to substantially compensate for warping of the sensor housing under changes in static line pressure.
5. A capacitive pressure transducer according to Claim 4 wherein the sensor housing and diaphragm means each have coefficients of elasticity and are of relative size so that the stress on the diaphragm means changes to provide a maximum error in output across the span of response of the transducer of less than 1% for each 1000 psi of static line pressure change on the diaphragm means at the same differential pressure across the diaphragm.
6. A capacitive pressure transducer according to Claim 4 wherein the sensor housing and diaphragm means material is selected so that the maximum error in output across the span of response of the transducer is less than .25% per 1000 psi of static line pressure change on the diaphragm means at the same differential pressure across the diaphragm means.
7. A capacitive pressure transducer according to Claim 4 wherein the sensor housing is formed from metal and includes the central cavity, the cavity being partially filled with a non-porous, insulating material forming an interface surface with the metal of the sensor housing, and the central chambers are each formed in the insulating material, the conductive surface portions of the central chambers being disposed on the insulating material, the interface surface of the insulating material and metal being positioned so as to be subjected to compression forces under static line pressures on the diaphragm means.
8. A capacitive pressure transducer according to Claim 1 wherein the sensor housing is electrically isolated from the transducer housing and the isolators.
9. A capacitive pressure transducer according to Claim 2 wherein the prestress on the diaphragm means is between 50,000 psi and 200,000 psi.
10. A capacitive pressure transducer according to Claim 1 and a support frame attached to the transducer housing, said isolators being mounted on said support frame at a location spaced from said transducer housing.
11. A capacitive pressure transducer according to Claim 1 wherein the separate passageway means comprise tubing which will bend under external load.
12. A capacitive pressure transducer including a sensor housing with an internal cavity, a deflectable, electrically conducting sensing diaphragm mounted on the sensor housing and dividing the cavity into first and second cavity sections, said sensor housing having a central axis lying generally normal to said diaphragm, a filling of insulation material in each of said cavity sections, said insulation material having recessed surfaces adjacent the diaphragm on opposite sides thereof to form chambers permitting deflection of said diaphragm under loads toward the respective recessed surface, means on the respective recessed surfaces forming capacitor plates which in combination with the diaphragm form first and second sensing capacitors generally symmetrical with each other relative to the diaphragm at a rest position having capacitance values C1 and C2, respectively, means including an isolator to provide pressure to opposite sides of said diaphragm tending to deflect said diaphragm when pressures on opposite sides are different from each other to thereby lower the capacitance value of one of the sensing capacitors and raise the value of the other sensing capacitor, the reference position of the diaphragm being reached when the pressure on opposite sides of the diaphragm is equal; characterized by the dimensions and the coefficients of elasticity of the diaphragm, the insulation material and the sensor housing in relation to the diaphragm diameter to insure that the product of diaphragm stretch times the capacitance spacing at rest position of the diaphragm remains substantially equal to a constant under changing pressures of equal magnitudes on opposite sides of said diaphragm.
13. A capacitive pressure transducer according to Claim 12 further characterized by the diaphragm being formed from a cobalt based, high strength stainless steel and the insulation material is an alkali-lead glass, and the housing is stainless steel.
14. A capacitive pressure transducer including a support frame, a sensor housing mounted on said frame, said sensor housing having a central chamber defined therein and a diaphragm having a conductive portion forming a first capacitor plate supported on the sensor housing and enclosing one portion of the chamber, said diaphragm being under an initial prestress of between 50,000 and 200,000 psi under atmospheric pressures, means forming a second capacitor plate on the surface defining said chamber and cooperating with said diaphragm to form a variable capacitor, said housing including second means enclosing a surface of said diaphragm opposite from said second capacitor plate, passageway means open through the plate means to said second means, and isolator means spaced from the sensor housing and having an isolator chamber defined therein, conduit means connecting the chamber in said isolator means to the passageway means, said passageway means, said isolator means and the second means enclosing said diaphragm being filled with a substantially incompressible fluid, said isolator chamber including at least one wall deflectable under pressure to transmit such pressure through the incompressible fluid to act upon said diaphragm, the diaphragm prestress and the sensor housing construction compensating the output capacitance signals.
15. A capacitive pressure transducer according to Claim 12, and a frame connected to the transducer housing, said isolator means being mounted on said frame at position spaced from said transducer housing.
16. A capacitive pressure transducer as specified in Claim 14 wherein said isolator means comprises an isolator housing, a chamber formed in said isolator housing, and a flexible diaphragm enclosing said chamber to form the deflectable wall.
17. The combination as specified in Claim 16 wherein said conduit means comprise tubing which will bend under external loads.
18. A variable reactance pressure transducer having an internal cavity, a deflectable sensing diaphragm mounted on the transducer and dividing the cavity into first and second cavity sections, said transducer having a central axis lying generally normal to said diaphragm, said cavity sections each being defined by cavity surfaces which taper from the diaphragm inwardly toward the central axis in direction away from the diaphragm, a filling of insulation material in each of said cavity sections, said insulation material having recessed surfaces adjacent the diaphragm on opposite sides thereof to form chambers permitting deflection of said diaphragm under loads toward the respective recessed surface, means to provide pressure to opposite sides of said diaphragm tending to deflect said diaphragm when pressures on opposite sides are different from each other, and means to sense the deflection of said diaphragm with respect to the recessed surfaces.
19. A pressure transducer as specified in Claim 18 wherein said insulation material is a glass or ceramic material bonded to the cavity surfaces.
20. A pressure transducer as specified in Claim 19 wherein said cavity surfaces are generally conical, and are generated about the central axis to form an included angle of between 20° and 70° with respect to the central axis.
21. A pressure transducer as specified in Claim 18 wherein the bond between the housing surfaces and the insulation material is substantially in compression.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/194,758 US4370890A (en) | 1980-10-06 | 1980-10-06 | Capacitive pressure transducer with isolated sensing diaphragm |
| US194,758 | 1980-10-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164240A true CA1164240A (en) | 1984-03-27 |
Family
ID=22718806
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000387283A Expired CA1164240A (en) | 1980-10-06 | 1981-10-05 | Capacitive pressure transducer with isolated sensing diaphragm |
Country Status (18)
| Country | Link |
|---|---|
| US (1) | US4370890A (en) |
| EP (1) | EP0061488B1 (en) |
| JP (1) | JPH046889B2 (en) |
| AU (1) | AU551166B2 (en) |
| BR (1) | BR8108830A (en) |
| CA (1) | CA1164240A (en) |
| FI (1) | FI72809C (en) |
| GB (1) | GB2099587B (en) |
| HK (1) | HK89885A (en) |
| HU (1) | HU190799B (en) |
| IL (1) | IL64028A (en) |
| IN (1) | IN154802B (en) |
| IT (1) | IT1193784B (en) |
| MX (1) | MX154961A (en) |
| SU (1) | SU1421266A3 (en) |
| WO (1) | WO1982001250A1 (en) |
| YU (1) | YU41525B (en) |
| ZA (1) | ZA816837B (en) |
Families Citing this family (99)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3213320A1 (en) * | 1982-04-06 | 1983-10-13 | Siemens AG, 1000 Berlin und 8000 München | PRESSURE OR PRESSURE DIFFERENTIAL TRANSMITTER |
| US4425799A (en) * | 1982-06-03 | 1984-01-17 | Kavlico Corporation | Liquid capacitance pressure transducer technique |
| US4539998A (en) * | 1983-04-29 | 1985-09-10 | American Hospital Supply Corporation | Pressure transducer assembly |
| USRE33518E (en) * | 1983-04-29 | 1991-01-15 | Baxter International, Inc. | Pressure transducer assembly |
| US4502003A (en) * | 1983-07-29 | 1985-02-26 | Rosemount Inc. | Two wire circuit having an adjustable span |
| US4612812A (en) * | 1985-08-15 | 1986-09-23 | Rosemount Inc. | Stress reducing stop for unstretched pressure sensing diaphragm |
| JPH043244Y2 (en) * | 1985-11-29 | 1992-02-03 | ||
| IL82194A (en) * | 1986-04-23 | 1992-03-29 | Rosemount Inc | Measurement circuit |
| US5083091A (en) * | 1986-04-23 | 1992-01-21 | Rosemount, Inc. | Charged balanced feedback measurement circuit |
| US4791352A (en) * | 1986-07-17 | 1988-12-13 | Rosemount Inc. | Transmitter with vernier measurement |
| US4745810A (en) * | 1986-09-15 | 1988-05-24 | Rosemount Inc. | Flangeless transmitter coupling to a flange adapter union |
| US4798089A (en) * | 1987-03-12 | 1989-01-17 | Rosemount Inc. | Isolator apparatus |
| US4760859A (en) * | 1987-05-18 | 1988-08-02 | Rosemount Inc. | Modular pressure instrument |
| US4833922A (en) * | 1987-06-01 | 1989-05-30 | Rosemount Inc. | Modular transmitter |
| US4818994A (en) * | 1987-10-22 | 1989-04-04 | Rosemount Inc. | Transmitter with internal serial bus |
| US5062302A (en) * | 1988-04-29 | 1991-11-05 | Schlumberger Industries, Inc. | Laminated semiconductor sensor with overpressure protection |
| JP2639159B2 (en) * | 1989-04-14 | 1997-08-06 | 富士電機株式会社 | Capacitive differential pressure detector |
| US4949581A (en) * | 1989-06-15 | 1990-08-21 | Rosemount Inc. | Extended measurement capability transmitter having shared overpressure protection means |
| US5022270A (en) * | 1989-06-15 | 1991-06-11 | Rosemount Inc. | Extended measurement capability transmitter having shared overpressure protection means |
| US4970898A (en) * | 1989-09-20 | 1990-11-20 | Rosemount Inc. | Pressure transmitter with flame isolating plug |
| US5134887A (en) * | 1989-09-22 | 1992-08-04 | Bell Robert L | Pressure sensors |
| DE3933512A1 (en) * | 1989-10-06 | 1991-04-18 | Endress Hauser Gmbh Co | DIFFERENTIAL PRESSURE MEASURING DEVICE |
| US5163326A (en) * | 1991-03-08 | 1992-11-17 | Rosemount Inc. | Line pressure compensator for a pressure transducer |
| US5184514A (en) * | 1991-07-12 | 1993-02-09 | Rosemount Inc. | Corrosion resistant isolator |
| US5230248A (en) * | 1991-07-12 | 1993-07-27 | Rosemount Inc. | Corrosion resistant isolator |
| US5237285A (en) * | 1991-10-18 | 1993-08-17 | Rosemount Inc. | Method and apparatus for capacitance temperature compensation and manufacturability in a dual plate capacitive pressure transmitter |
| US5271277A (en) * | 1991-12-23 | 1993-12-21 | The Boc Group, Inc. | Capacitance pressure transducer |
| US5329818A (en) * | 1992-05-28 | 1994-07-19 | Rosemount Inc. | Correction of a pressure indication in a pressure transducer due to variations of an environmental condition |
| US5596147A (en) * | 1995-11-17 | 1997-01-21 | Wilda; Douglas W. | Coplanar pressure sensor mounting for remote sensor |
| US5757608A (en) * | 1996-01-25 | 1998-05-26 | Alliedsignal Inc. | Compensated pressure transducer |
| US5741975A (en) * | 1996-07-31 | 1998-04-21 | Motorola, Inc. | Media isolated differential pressure sensor and fluid injection method |
| US6047244A (en) * | 1997-12-05 | 2000-04-04 | Rosemount Inc. | Multiple range transition method and apparatus for process control sensors |
| US6038961A (en) * | 1998-03-02 | 2000-03-21 | Rosemount Inc. | Flush mount remote seal |
| US6295875B1 (en) | 1999-05-14 | 2001-10-02 | Rosemount Inc. | Process pressure measurement devices with improved error compensation |
| US6328647B1 (en) | 2000-04-06 | 2001-12-11 | Jon E. Traudt | Pressure differential detecting system, and method of use |
| DE10050300A1 (en) * | 2000-10-10 | 2002-04-11 | Endress Hauser Gmbh Co | pressure measuring cell |
| US6516672B2 (en) | 2001-05-21 | 2003-02-11 | Rosemount Inc. | Sigma-delta analog to digital converter for capacitive pressure sensor and process transmitter |
| FR2830612B1 (en) * | 2001-10-10 | 2004-01-23 | Bosch Gmbh Robert | RACE SENSOR, PNEUMATIC SERVOMOTOR INCLUDING THE SAME, AND BRAKING SYSTEM COMPRISING SUCH A SERVOMOTOR |
| DE10152681A1 (en) * | 2001-10-19 | 2003-04-30 | Endress & Hauser Gmbh & Co Kg | Diaphragm seal with separating membrane and process for its manufacture |
| JP4163880B2 (en) * | 2002-03-05 | 2008-10-08 | 長野計器株式会社 | Differential pressure detector, flow meter and liquid level meter equipped with the differential pressure detector |
| US6839546B2 (en) | 2002-04-22 | 2005-01-04 | Rosemount Inc. | Process transmitter with wireless communication link |
| US6843133B2 (en) * | 2002-06-18 | 2005-01-18 | Rosemount, Inc. | Capacitive pressure transmitter |
| DE10229703A1 (en) * | 2002-07-02 | 2004-01-15 | Endress + Hauser Gmbh + Co. Kg | Capacitive pressure sensor |
| DE102004006383A1 (en) * | 2004-02-09 | 2005-08-25 | Endress + Hauser Gmbh + Co. Kg | Differential pressure sensor with overload diaphragm |
| WO2005086331A2 (en) * | 2004-03-02 | 2005-09-15 | Rosemount, Inc. | Process device with improved power generation |
| DE102004017580A1 (en) * | 2004-04-07 | 2005-12-01 | Endress + Hauser Gmbh + Co. Kg | Differential pressure sensor with dynamic overload protection |
| US8538560B2 (en) * | 2004-04-29 | 2013-09-17 | Rosemount Inc. | Wireless power and communication unit for process field devices |
| US8145180B2 (en) * | 2004-05-21 | 2012-03-27 | Rosemount Inc. | Power generation for process devices |
| US8160535B2 (en) * | 2004-06-28 | 2012-04-17 | Rosemount Inc. | RF adapter for field device |
| US7262693B2 (en) * | 2004-06-28 | 2007-08-28 | Rosemount Inc. | Process field device with radio frequency communication |
| US7213464B1 (en) | 2004-10-25 | 2007-05-08 | Traudt Jon E | System for visually monitoring pressure in an enclosed space |
| US7680460B2 (en) * | 2005-01-03 | 2010-03-16 | Rosemount Inc. | Wireless process field device diagnostics |
| US9184364B2 (en) * | 2005-03-02 | 2015-11-10 | Rosemount Inc. | Pipeline thermoelectric generator assembly |
| US7334484B2 (en) * | 2005-05-27 | 2008-02-26 | Rosemount Inc. | Line pressure measurement using differential pressure sensor |
| US8452255B2 (en) | 2005-06-27 | 2013-05-28 | Rosemount Inc. | Field device with dynamically adjustable power consumption radio frequency communication |
| US7379792B2 (en) * | 2005-09-29 | 2008-05-27 | Rosemount Inc. | Pressure transmitter with acoustic pressure sensor |
| US7415886B2 (en) * | 2005-12-20 | 2008-08-26 | Rosemount Inc. | Pressure sensor with deflectable diaphragm |
| US7308830B2 (en) * | 2006-01-26 | 2007-12-18 | Rosemount Inc. | Pressure sensor fault detection |
| US7913566B2 (en) | 2006-05-23 | 2011-03-29 | Rosemount Inc. | Industrial process device utilizing magnetic induction |
| US8188359B2 (en) * | 2006-09-28 | 2012-05-29 | Rosemount Inc. | Thermoelectric generator assembly for field process devices |
| ITMI20070191A1 (en) * | 2007-02-05 | 2008-08-06 | Abb Service Srl | PRESSURE TRANSMITTER FOR DETECTION OF A VARIABLE RELATED TO A PROCESS FLUID. |
| US8898036B2 (en) * | 2007-08-06 | 2014-11-25 | Rosemount Inc. | Process variable transmitter with acceleration sensor |
| US7624642B2 (en) * | 2007-09-20 | 2009-12-01 | Rosemount Inc. | Differential pressure sensor isolation in a process fluid pressure transmitter |
| US7484416B1 (en) | 2007-10-15 | 2009-02-03 | Rosemount Inc. | Process control transmitter with vibration sensor |
| US7578194B1 (en) * | 2008-02-11 | 2009-08-25 | Sensata Technologies, Inc. | Differential fluid pressure measurement apparatus |
| US7743662B2 (en) * | 2008-02-14 | 2010-06-29 | Kulite Semiconductor Products, Inc. | Low differential pressure transducer |
| US8191424B2 (en) * | 2008-02-14 | 2012-06-05 | Kulite Semiconductor Products, Inc. | Low differential pressure transducer |
| WO2009154748A2 (en) * | 2008-06-17 | 2009-12-23 | Rosemount Inc. | Rf adapter for field device with low voltage intrinsic safety clamping |
| US8250924B2 (en) | 2008-04-22 | 2012-08-28 | Rosemount Inc. | Industrial process device utilizing piezoelectric transducer |
| US8847571B2 (en) | 2008-06-17 | 2014-09-30 | Rosemount Inc. | RF adapter for field device with variable voltage drop |
| US8929948B2 (en) * | 2008-06-17 | 2015-01-06 | Rosemount Inc. | Wireless communication adapter for field devices |
| US8049361B2 (en) * | 2008-06-17 | 2011-11-01 | Rosemount Inc. | RF adapter for field device with loop current bypass |
| US8694060B2 (en) * | 2008-06-17 | 2014-04-08 | Rosemount Inc. | Form factor and electromagnetic interference protection for process device wireless adapters |
| US7977924B2 (en) * | 2008-11-03 | 2011-07-12 | Rosemount Inc. | Industrial process power scavenging device and method of deriving process device power from an industrial process |
| US7954383B2 (en) * | 2008-12-03 | 2011-06-07 | Rosemount Inc. | Method and apparatus for pressure measurement using fill tube |
| US8327713B2 (en) | 2008-12-03 | 2012-12-11 | Rosemount Inc. | Method and apparatus for pressure measurement using magnetic property |
| US7870791B2 (en) * | 2008-12-03 | 2011-01-18 | Rosemount Inc. | Method and apparatus for pressure measurement using quartz crystal |
| US9674976B2 (en) * | 2009-06-16 | 2017-06-06 | Rosemount Inc. | Wireless process communication adapter with improved encapsulation |
| US8626087B2 (en) * | 2009-06-16 | 2014-01-07 | Rosemount Inc. | Wire harness for field devices used in a hazardous locations |
| US8371175B2 (en) * | 2009-10-01 | 2013-02-12 | Rosemount Inc. | Pressure transmitter with pressure sensor mount |
| US8429978B2 (en) | 2010-03-30 | 2013-04-30 | Rosemount Inc. | Resonant frequency based pressure sensor |
| US8234927B2 (en) | 2010-06-08 | 2012-08-07 | Rosemount Inc. | Differential pressure sensor with line pressure measurement |
| US8132464B2 (en) | 2010-07-12 | 2012-03-13 | Rosemount Inc. | Differential pressure transmitter with complimentary dual absolute pressure sensors |
| US10761524B2 (en) | 2010-08-12 | 2020-09-01 | Rosemount Inc. | Wireless adapter with process diagnostics |
| US8384915B2 (en) | 2010-10-01 | 2013-02-26 | Rosemount Inc. | Test block for use in a welding process |
| US9310794B2 (en) | 2011-10-27 | 2016-04-12 | Rosemount Inc. | Power supply for industrial process field device |
| DE102012103585A1 (en) * | 2012-04-24 | 2013-10-24 | Endress + Hauser Gmbh + Co. Kg | pressure transducers |
| US8752433B2 (en) | 2012-06-19 | 2014-06-17 | Rosemount Inc. | Differential pressure transmitter with pressure sensor |
| US9048901B2 (en) | 2013-03-15 | 2015-06-02 | Rosemount Inc. | Wireless interface within transmitter |
| RU2545085C1 (en) * | 2013-11-12 | 2015-03-27 | Закрытое акционерное общество Промышленная группа "Метран" | Design of biplanar capacitance sensor of pressure difference |
| US9316553B2 (en) * | 2014-03-26 | 2016-04-19 | Rosemount Inc. | Span line pressure effect compensation for diaphragm pressure sensor |
| US9857259B2 (en) * | 2014-09-30 | 2018-01-02 | Rosemount Inc. | Differential pressure sensor with high pressure capabilities |
| DE102015117222A1 (en) * | 2014-10-10 | 2016-04-14 | Steering Solutions Ip Holding Corporation | Dual-channel pressure sensor with a single connection opening |
| DE102014119407A1 (en) | 2014-12-22 | 2016-06-23 | Endress + Hauser Gmbh + Co. Kg | Differential pressure sensor and differential pressure transducer with such a differential pressure sensor |
| US10126193B2 (en) * | 2016-01-19 | 2018-11-13 | Rosemount Aerospace Inc. | Compact or miniature high temperature differential pressure sensor capsule |
| CN107976279A (en) * | 2017-12-15 | 2018-05-01 | 北京创昱科技有限公司 | A kind of vacuum measuring device |
| US11371899B2 (en) | 2018-05-17 | 2022-06-28 | Rosemount Inc. | Measuring element with an extended permeation resistant layer |
| US11041773B2 (en) * | 2019-03-28 | 2021-06-22 | Rosemount Inc. | Sensor body cell of a pressure sensor |
| CN110553763B (en) * | 2019-09-10 | 2021-03-19 | 广州敏华仪器仪表有限公司 | Coplanar suspension type full-isolation sensor |
Family Cites Families (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1582509A (en) * | 1968-05-17 | 1969-10-03 | ||
| US3618390A (en) * | 1969-10-27 | 1971-11-09 | Rosemount Eng Co Ltd | Differential pressure transducer |
| DE2230264A1 (en) * | 1972-06-21 | 1974-01-31 | Union Rheinische Braunkohlen | PROCESS FOR THE PRODUCTION OF AROMATIC OR HYDROAROMATIC HYDROPEROXIDES |
| US3793885A (en) * | 1972-09-05 | 1974-02-26 | Rosemount Inc | Diaphrgam construction for differential pressure transducer |
| JPS5617720B2 (en) * | 1972-12-25 | 1981-04-23 | ||
| US3869920A (en) * | 1973-04-13 | 1975-03-11 | Yokogawa Electric Works Ltd | Symmetrically arranged, deflection type differential pressure transmitters for controlling industrial systems and processes |
| US3808480A (en) * | 1973-04-16 | 1974-04-30 | Bunker Ramo | Capacitive pressure transducer |
| SU506223A1 (en) * | 1973-06-18 | 1982-09-30 | Государственный научно-исследовательский институт теплоэнергетического приборостроения | Membrane unit |
| SU506224A1 (en) * | 1973-06-18 | 1982-09-30 | Государственный научно-исследовательский институт теплоэнергетического приборостроения | Pressure differential transducer |
| US3926055A (en) * | 1973-10-01 | 1975-12-16 | Itt | Mechanical span and zero adjustment apparatus for pressure transducers |
| JPS5232368Y2 (en) * | 1973-10-30 | 1977-07-23 | ||
| US3999435A (en) * | 1975-04-24 | 1976-12-28 | Fischer & Porter Co. | Differential pressure transmitter |
| US4111056A (en) * | 1975-06-30 | 1978-09-05 | Michael Mastromatteo | Control devices |
| JPS5232368U (en) * | 1975-08-29 | 1977-03-07 | ||
| JPS5233575A (en) * | 1975-09-09 | 1977-03-14 | Fuji Electric Co Ltd | Differential pressure measuring device |
| US3994166A (en) * | 1975-11-10 | 1976-11-30 | Warren Automatic Tool Co. | Apparatus for eliminating differential pressure surges |
| CA1077294A (en) * | 1976-05-03 | 1980-05-13 | Honeywell Inc. | Pressure transmitter with simplified pressure sensing head |
| US4072058A (en) * | 1976-05-03 | 1978-02-07 | Honeywell Inc. | Differential pressure transmitter with pressure sensor protection |
| JPS5829862B2 (en) * | 1977-05-14 | 1983-06-25 | 富士電機株式会社 | pressure measuring device |
| JPS5831855B2 (en) * | 1977-06-22 | 1983-07-08 | 富士電機株式会社 | Manufacturing method of pressure measuring device |
| DE2824489C2 (en) * | 1978-06-03 | 1982-06-16 | Reifen-Ihle GmbH, 8870 Günzburg | Pipe connector for crossing pipes |
| DE2827274A1 (en) * | 1978-06-21 | 1980-01-10 | Fuji Electric Co Ltd | Pressure measuring device with temp. compensation - has sealing diaphragm which is more flexible than measuring diaphragm |
| US4218925A (en) * | 1979-06-27 | 1980-08-26 | Honeywell Inc. | Differential pressure transmitter with pressure sensor protection |
| US4285244A (en) * | 1980-02-13 | 1981-08-25 | Honeywell Inc. | Non-symmetrical overload protection device for differential pressure transmitter |
-
1980
- 1980-10-06 US US06/194,758 patent/US4370890A/en not_active Expired - Lifetime
-
1981
- 1981-10-01 IN IN1104/CAL/81A patent/IN154802B/en unknown
- 1981-10-02 HU HU821844A patent/HU190799B/en unknown
- 1981-10-02 JP JP56503341A patent/JPH046889B2/ja not_active Expired - Lifetime
- 1981-10-02 YU YU2389/81A patent/YU41525B/en unknown
- 1981-10-02 ZA ZA816837A patent/ZA816837B/en unknown
- 1981-10-02 EP EP81902809A patent/EP0061488B1/en not_active Expired
- 1981-10-02 AU AU77203/81A patent/AU551166B2/en not_active Expired
- 1981-10-02 GB GB8213814A patent/GB2099587B/en not_active Expired
- 1981-10-02 WO PCT/US1981/001329 patent/WO1982001250A1/en active IP Right Grant
- 1981-10-02 BR BR8108830A patent/BR8108830A/en not_active IP Right Cessation
- 1981-10-05 CA CA000387283A patent/CA1164240A/en not_active Expired
- 1981-10-05 IT IT49423/81A patent/IT1193784B/en active
- 1981-10-06 MX MX189512A patent/MX154961A/en unknown
- 1981-10-11 IL IL64028A patent/IL64028A/en not_active IP Right Cessation
-
1982
- 1982-06-03 FI FI821976A patent/FI72809C/en not_active IP Right Cessation
- 1982-06-04 SU SU823453803A patent/SU1421266A3/en active
-
1985
- 1985-11-14 HK HK898/85A patent/HK89885A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| IN154802B (en) | 1984-12-15 |
| IL64028A (en) | 1987-12-20 |
| SU1421266A3 (en) | 1988-08-30 |
| WO1982001250A1 (en) | 1982-04-15 |
| EP0061488B1 (en) | 1986-12-17 |
| AU551166B2 (en) | 1986-04-17 |
| EP0061488A4 (en) | 1983-10-04 |
| YU238981A (en) | 1983-12-31 |
| HU190799B (en) | 1986-11-28 |
| MX154961A (en) | 1988-01-14 |
| IT8149423A0 (en) | 1981-10-05 |
| JPH046889B2 (en) | 1992-02-07 |
| EP0061488A1 (en) | 1982-10-06 |
| FI821976A0 (en) | 1982-06-03 |
| GB2099587B (en) | 1984-11-07 |
| US4370890A (en) | 1983-02-01 |
| HK89885A (en) | 1985-11-22 |
| BR8108830A (en) | 1982-08-24 |
| ZA816837B (en) | 1982-09-29 |
| IT1193784B (en) | 1988-08-24 |
| AU7720381A (en) | 1982-04-28 |
| GB2099587A (en) | 1982-12-08 |
| FI72809C (en) | 1987-07-10 |
| FI72809B (en) | 1987-03-31 |
| YU41525B (en) | 1987-08-31 |
| JPS57501494A (en) | 1982-08-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1164240A (en) | Capacitive pressure transducer with isolated sensing diaphragm | |
| EP0041886B1 (en) | Capacitive pressure transducer | |
| US4603371A (en) | Capacitive sensing cell made of brittle material | |
| US5157972A (en) | Pressure sensor with high modules support | |
| US5134887A (en) | Pressure sensors | |
| CA1264419A (en) | Temperature compensated pressure transducer | |
| US4163395A (en) | Pressure transmitter with simplified pressure sensing head | |
| GB1581903A (en) | Capacitor transducer | |
| JPH11501123A (en) | Pressure sensors and pressure transmitters | |
| US4203327A (en) | Piezoresistive silicon strain sensors and pressure transducers incorporating them | |
| WO1985002676A1 (en) | Pressure sensor with a substantially flat overpressure stop for the measuring diaphragm | |
| US3035240A (en) | Beam-diaphragm pressure load cell improvements | |
| US4741214A (en) | Capacitive transducer with static compensation | |
| JPS5829862B2 (en) | pressure measuring device | |
| US4172387A (en) | Pressure responsive apparatus | |
| JPH0578775B2 (en) | ||
| KR900001465B1 (en) | Capacitive pressure transducer with isolated sensing diapharm | |
| EP0775303A1 (en) | Pressure gauge | |
| NO156188B (en) | CAPACITY PRESSURE TRANSDUCTOR. | |
| JP2546013B2 (en) | Capacitive differential pressure detector | |
| IE55965B1 (en) | Pressure transducer | |
| GB2266963A (en) | Capacitive differential pressure detector | |
| JPS62238432A (en) | Differential pressure transmitter | |
| JPS5831853B2 (en) | Differential pressure measuring device | |
| JPS5972035A (en) | Differential pressure and pressure transmitter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |