GB2311137A - Piezoelectric stress gauge - Google Patents
Piezoelectric stress gauge Download PDFInfo
- Publication number
- GB2311137A GB2311137A GB9605390A GB9605390A GB2311137A GB 2311137 A GB2311137 A GB 2311137A GB 9605390 A GB9605390 A GB 9605390A GB 9605390 A GB9605390 A GB 9605390A GB 2311137 A GB2311137 A GB 2311137A
- Authority
- GB
- United Kingdom
- Prior art keywords
- electrode
- electrode assembly
- stress gauge
- gauge
- disk
- 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.)
- Granted
Links
- 239000004593 Epoxy Substances 0.000 claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 8
- 230000008054 signal transmission Effects 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 11
- 238000005530 etching Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000010453 quartz Substances 0.000 abstract description 36
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 36
- 230000005540 biological transmission Effects 0.000 abstract 1
- 239000004411 aluminium Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 238000010276 construction Methods 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 238000005488 sandblasting Methods 0.000 description 2
- 150000001398 aluminium Chemical class 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
-
- 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
- G01L9/008—Transmitting or indicating the displacement of flexible diaphragms using piezoelectric devices
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Fluid Pressure (AREA)
Abstract
A one-dimensional piezoelectric stress gauge has an electrode assembly 2 provided as an independent unit which is attached to the slab of piezoelectric material 3 e.g. by an epoxy bond. The preferred piezoelectric material is quartz provided in the form of a disk. The electrode assembly 2 may be provided by a printed circuit board onto which the electrode configuration has been etched. As described the side of the p.c.b. bonded to the quartz disk 3 carries a circular central electrode (9, Fig.2) surrounded by a guard ring (10). The other face carries an earth ring (18). The output is taken to a terminal socket 7 via a transmission line 6 connected to the earth ring and (by a through-the-board connection) to the central electrode (9). The invention avoids the need to machine an insulating gap in a deposited electrode layer to separate the central electrode from the guard ring.
Description
PIEZOELECTRIC STRESS GAUGE
The present invention relates to piezoelectric stress gauges and in particular to one dimensional configurations of such gauges. When using a piezoelectric stress gauge to study intrinsic physical properties where undistorted gauge records are required, a one dimensional configuration is used ie. a gauge in which one dimensional mechanical strain conditions and a one dimensional electric field is obtained.
The principles upon which one dimensional stress gauges are constructed are described in "Piezoelectric Current from Shock-Loaded Quartz - A Submicrosecond Stress Gauge" (J.Appl.Phys., Vol. 36, No.5, p 1775-1783, May 1965).
Known one dimensional stress gauges comprise a quartz disk onto which an electrode layer is vapour deposited. An insulating ring is then either ground or sand blasted into the surface of the disk electrically isolating the inner and outer portions of the disk electrode. This electrode configuration is known as a guard ring arrangement. The present invention relates particularly to the formation of this type of electrode configuration on the surface of the quartz disk.
A disadvantage of the known guard ring construction is the requirement to use expensive vapour deposition and grinding techniques to produce the required electrode and insulating ring configuration. If the insulating ring is ground too deeply into the quartz disk, it will result in distortion of the impact response of the quartz. If the insulating ring is not ground sufficiently deeply, the conductivity between the inner and outer electrode areas will not be reduced sufficiently and the one-dimensional response of the gauge will be adversely affected.
Another disadvantage of the known techniques arises from the requirement to plate the electrodes directly onto the quartz disk. If the formation of the electrode or insulating ring prove inadequate for any reason, the quartz disks have to be discarded or recovered by further processing.
Accordingly, the present invention provides a one dimensional stress gauge having an electrode assembly and a slab of piezoelectric material wherein the electrode assembly is an independent unit attached to the piezoelectric slab.
An advantage of this construction is that the electrode assembly can be checked for defects prior to being attached to the piezoelectric slab.
The applicant has found that forming the electrode assembly independently of the piezoelectric slab and then joining these two components together does not adversely affect the response of the stress gauge compared to the performance of equivalent gauges in which the electrode configuration is formed directly onto a quartz disk by vapour deposition and grinding or sand blasting techniques (see "Quartz Gauge Response in Ion Radiation" by Taylor,
Jilbert, Kernthaler and Lee - Presented American Physical
Society Conference, Washingtin State USA, August 1995).
The piezoelectric disk and electrode assembly may be joined together by clips, adhesive or other joining techniques.
In one embodiment of the invention, a quartz disk and electrode assembly are joined by conventional epoxy bonding techniques. The applicant has shown that the thin layer of epoxy does not affect the performance of the gauge as the quartz disk and electrodes do not need to be in electrical contact (ie. the signal in the electrodes is induced capacitatively and the thin layer of adhesive is not detrimental to this induction.)
According to one aspect of the invention, the electrode assembly is provided by a printed circuit board (PCB) which has been etched to provide the required guard ring electrode configuration. This construction has the advantage that a large number of electrode assemblies can be produced to close tolerances without the requirement for expensive and complex plating and grinding techniques.
In this way, the performance problems which can arise as a result of the grinding or sandblasting of the insulating ring are overcome. Also, due to the flexibility of PCB etching techniques, different electrode patterns can be readily produced and these patterns can be more complicated than the existing guard ring electrode configuration should this prove desirable. For example, the electrode assembly may comprise multiple tiled electrode pads, each pad having the possibility of connection to an independant signal transmission line.
The PCB construction may be further improved by the addition of suitably located, plated through holes in the
PCB which facilitate easy connection of the signal transmission line or lines to the stress gauge electrodes.
In existing one-dimensional stress gauges the signal transmission lines are soldered directly onto the vapour deposited electrodes which can result in deterioration of the electrodes. The provision of plated through holes in the PCB allows the connection of the signal transmission lines without the need for soldering directly onto the electrodes.
One embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
Figure 1 is a section through a guard ring quartz gauge, showing the quartz disk and guard ring electrode assembly.
Figure 2 is a partially cut away front elevation of the quartz gauge assembly.
Figure 3 is a section through the side elevation of the quartz gauge assembly showing details of the quartz disk and guard ring electrode assembly.
Figure 4 is a rear elevation of the guard ring electrode assembly.
Referring to Figure 1, the guard ring quartz gauge comprises a body 1 within which the guard ring electrode assembly 2 and quartz disk 3 are located against a plug of hard epoxy 4. Aluminium flashing or a vapour deposited aluminium layer covers the measuring face of the gauge and acts as an earth electrode 5. A signal transmission line 6 is connected to the guard ring electrode assembly 2 and terminates in a socket 7 which is located in the lid of the gauge 8. Sufficient slack is provided in the signal transmission line 6 so that the lid of the gauge 8 can be removed from the body 1 without the need to disconnect the signal transmission line 6 from the socket 7.
Referring to Figures 2 and 3, the guard ring electrode assembly 2 is provided by a double sided PCB onto which the electrode configuration has been etched. The electrode configuration comprises an inner electrode 9 and an outer electrode 10, separated by an insulating gap 11.
The quartz disk 3 and electrode assembly 2 are held together by an epoxy bond 13. The electrode assembly 2 is provided with three location lugs 12 which locate the assembly in the body 1 of the gauge on plugs of hard epoxy 12a.
Finally, referring to Figure 4, the rear elevation of the PCB is etched with an earth annulus 18. Three earth straps 17 connect the earth annulus 18 to the aluminium earth electrode 5 on the measuring face of the gauge. The signal transmission line 6 is connected to the inner electrode 9, via plated through hole 14 in the PCB, and to the spur on the earth annulus 18.
The outer electrode 10 is connected to the earth annulus 18 via resistor 16 which is sized such that the potential on the inner electrode 9 and outer electrode 10 is kept approximately the same.
The construction of the stress gauge is carried out as follows : Referring to Figures 2, 3 and 4, the electrode assembly 2 is provided by a double sided PCB which has been etched to provide on one side1 the inner electrode 9, outer electrode 10 and insulating gap 11 and on the other side the earth ring 18. Plated through holes 14 and 15 provide electrical contact from the inner electrode 9 and outer electrode 10 respectively to the other side of the
PCB. The electrode assembly 2 is joined to a prepared quartz disk 3 via an epoxy bond 13 between one face of the quartz disk 3 and the face of the PCB onto which the inner electrode 9 and outer electrode 10 have been etched.
Three nickel earth straps 17 are soldered to the earth annulus 18, equispaced between the location lugs 12. The strips are folded tautly over the PCB and epoxy bonded to the edge of the composite measuring head comprising the electrode assembly 2 and quartz disk 3. The earth straps 17 are cut off flush with the measuring surface of the quartz disk 3, ready for connection to the earth electrode 5. The signal transmission line 6 is soldered to the spur on the earth annulus 18 and to the plated through hole 14.
In order that buffers may be placed on the surface of the quartz disk 3 without bottoming on the end of the gauge body 1, the quartz disk 3 is mounted at least O.05mm proud of the end of the body 1. A 0.05mum thick annulus is placed around the quartz disk 3 and one drop of epoxy resin 12a is placed on each of the location lugs 12. The body is lowered over the quartz disk 3 and electrode assembly 2 until it rests on the 0.05mm thick annulus.
Once the epoxy resin has cured, the annulus is removed and the 0.05mm clearance gap between the surface of the quartz disk 3 and the end of the body 1 is confirmed.
Hard epoxy 4 is used to pot the electrode assembly 2, quartz disk 3 and signal transmission line 6 into the body of the gauge 1. Any gaps remaining between the quartz disk 3 and body of the gauge 1 are filled with soft epoxy 19. A film of aluminium is vapour deposited over the measuring face of the quartz disk 3 to form the earth electrode 5. This aluminium film makes electrical contact with the earth strips 17 and the gauge body 1.
Finally, referring to Figure 1, the signal transmission line 6 is terminated in the socket 7 which is located in the lid of the gauge 8. The lid 8 is then attached to the body of the gauge 1 by means of screws or other attachment means.
It will be realised that the electrode assembly 2 may be provided by a single sided PCB onto which the electrode configuration has been etched. In this case, the signal transmission line 6, earth straps 17 and resistors 16 will have to be hard wired to the relevant sections of the etched electrodes 9, 10.
The electrode assembly 2 may also be provided by conducting foil that has been cut to the required dimensions and bonded either directly to the quartz disk 3 or to a substrate which is subsequently bonded to the quartz disk 3.
Finally, the quartz disk 3 may be substituted by a disk of different piezoelectric material such as piezoelectric plastic provided the material has the necessary response characteristics.
Claims (9)
1. A one dimensional stress gauge having an electrode assembly and a slab of piezoelectric material wherein the electrode assembly is an independent unit attached to the piezoelectric slab.
2. A one dimensional stress gauge as claimed in claim 1 wherein the piezoelectric slab and electrode assembly are attached by an epoxy bond.
3. A one dimensional stress gauge as claimed in any of the preceding claims wherein the electrode assembly is provided by a printed circuit board onto which an electrode configuration has been etched.
4. A one dimensional stress gauge as claimed in claim 3 wherein the printed circuit board is provided with one or more plated through holes to facilitate the attachment of one or more signal transmission lines.
5. A one dimensional stress gauge as claimed in any of the preceding claims wherein the slab of peizoelectric material is formed in the shape of a disk.
6. A method of producing a one dimensional stress gauge including the steps of a. Production of an electrode assembly as an independent unit; b. Attaching the electrode assembly to a prepared disk of piezoelectric material.
7. A method of producing a one dimensional stress gauge as claimed in claim 5 wherein the electrode assembly is produced by etching a printed circuit board with an electrode configuration.
8. A method as claimed in claims 5 or 6 wherein the electrode assembly is joined to the piezoelectric disk by standard epoxy bonding techniques.
9. A one dimensional stress gauge as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9605390A GB2311137B (en) | 1996-03-14 | 1996-03-14 | Piezoelectric stress gauge |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9605390A GB2311137B (en) | 1996-03-14 | 1996-03-14 | Piezoelectric stress gauge |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9605390D0 GB9605390D0 (en) | 1996-05-15 |
| GB2311137A true GB2311137A (en) | 1997-09-17 |
| GB2311137B GB2311137B (en) | 2000-02-23 |
Family
ID=10790397
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9605390A Expired - Fee Related GB2311137B (en) | 1996-03-14 | 1996-03-14 | Piezoelectric stress gauge |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2311137B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB366252A (en) * | ||||
| GB571904A (en) * | 1943-01-11 | 1945-09-13 | Brush Dev Co | Improvements in or relating to piezoelectric transducers |
-
1996
- 1996-03-14 GB GB9605390A patent/GB2311137B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB366252A (en) * | ||||
| GB571904A (en) * | 1943-01-11 | 1945-09-13 | Brush Dev Co | Improvements in or relating to piezoelectric transducers |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9605390D0 (en) | 1996-05-15 |
| GB2311137B (en) | 2000-02-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20010314 |