CA1149629A - Thin film strain gage with unstrained temperature compensation resistances - Google Patents
Thin film strain gage with unstrained temperature compensation resistancesInfo
- Publication number
- CA1149629A CA1149629A CA000364337A CA364337A CA1149629A CA 1149629 A CA1149629 A CA 1149629A CA 000364337 A CA000364337 A CA 000364337A CA 364337 A CA364337 A CA 364337A CA 1149629 A CA1149629 A CA 1149629A
- Authority
- CA
- Canada
- Prior art keywords
- thin film
- strain gage
- resistance
- temperature compensation
- bridge
- 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
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Abstract
ABSTRACT OF THE DISCLOSURE
A thin film strain gage transducer includes tem-perature compensation resistances on an unstrained portion of the flexure element of the transducer. The compensation resistances are formed of the same material as the electrical leads interconnecting the strain gage resistances and also are deposited simultaneously with the electrical leads dur-ing manufacture.
A thin film strain gage transducer includes tem-perature compensation resistances on an unstrained portion of the flexure element of the transducer. The compensation resistances are formed of the same material as the electrical leads interconnecting the strain gage resistances and also are deposited simultaneously with the electrical leads dur-ing manufacture.
Description
BACKGROUND OF THE INVENTION
This invention relates to a thin film strain gage apparatus.
Force transducers embodying thin film strain gaga resistance bridges have been in use for many years. Typical-ly, the gages are provided on a flexure element which deforms in response to an applied force. In such cases, temperature effects may cause unequal expansion of the legs of the bridge even when no actual force is being applied. This cau-ses a shift in the zero point of the bridge since an output will be produced even when no force is applied. Similarly, temperature effects may result in differential changes in the elasticity or spring constant of various parts of the trans-ducer, so that a given deflection of the flexure element will cause different bridge outputs as the temperature varies.
This causes a shift in the span of the bridge, also known as the gage factor or sensitivity.
Various approaches to compensation for temperature effects have been followed in the past. Bodner et al dis-closed in U.S. Patent 2,930,224 a type of temperature compen-sating strain gage in which a strain-insensitive thermocouple is used to generate a current flow opposite to that flowing in the gage resistance in order to cancel out temperature ef-fects. The temperature compensating elements, however, are lo-cated on the strained portion of the flexure element and there-fore in fact are subject to resistanoe variations due to applied strain.
Starr also disclosed in U.S. Patent 3,034,346 a technique for ~k ~D-7073 ~ rl¢~ ~z~
compensation of strain gage nonlinearity in which the compen-sating resistances are placed on the strained portion of the flexure element. Billette et al show in U.S. Patent No.
3,886,799 a type of semiconductor pressure transducer in which compensating elements are provided on the flexure element with the strain gage bridge.
While these prior art devices have achieved a mea-sure of success in compensating for temperature effects, the location of the compensating elements on the strained portion of the flexure element causes resistance variations due to strain which tend to interfere with the desired function of the compensating elements: the minimization of temperature effects. Moreover, due to the complicated procedures by which prior art thin film strain gage transducers have been made, manufacturing time has been rather long and cost high.
OBJECTS OF THE INVENTION
An object of the invention is to provide an improved thin film strain gage transducer havin~ provision for tempera-ture compensation.
Another object of the invention is to provide such a transducer in which the compensating elements are not subject ta applied strain which would influence their performance.
Still another object of the invention is to provide such a transducer in which the structure of the strain gages and compensating elements is quite simple, thereby facilitat-ing quick and less expensive manufacture.
These objects are given only by way of example;
thus, other desirable objectives and advantages inherently achieved by the disclosed invention may occur to those skilled in the art. Nonetheless, the scope of protection is to be limited only by the appended claims.
SUMMARY OF THE INVENTION
The above objects and other advantages are achieved with the invention which comprises, in one embodiment, a flexure element having at least one thin film strain gage 3~
resistance element deposited thereon in a position to be strained upon deformation of the flexure element. Leads of a material having a temperature coefficient of resistance opposite to that of the strain gage resistances are attached to the gages. Temperature compensation resistors are f~rmed in the leads and deposited at a location on the flexure ele-ment which is unstrained during operation. A bridge of the strain gages is usually used. Due to the simplified process used to make the transducer, the leads are superposed on an underlying thin layer of the same material as the strain gage resistances.
As used in this application, the term "thin film"
refers to elements of minute thickness which are deposited using sputtering or vacuum deposition techniques. The thick-ness of such films is typically measured in Angstrom unitsor microns so that several layers of such "thin films" may have a thickness of only 4 to 30 microns and an individual layer may have a thickness of about 200 Angstrom units to 1 micron. Such thin film elements are used in integrated cir-cuits and are readily distinguishable from discrete elementsor, as in the case of strain gages, from bonded gages or wire gages.
BRIEF DESCRIPTION OF THE DRAWING
-Figure 1 shows a greatly enlarged, perspective view of a flexure element having deposited thereon a temperature compensated strain gage bridge according to the present in-vention.
Figure 2 shows a schematic diagram of the bridge illustrated in Figure 1.
Figure 3 shows a greatly enlarged cross-section taken along line 3-3 in Figure 1, indicating portions of the individual thin films deposited to form the bridge strain gage resistances and electrical leads.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The following is a detailed description of the . .
6~
invention, reference being made to the drawing in which like reference numerals identify like elements of structure in each of the several Figures.
Referring to Figures 1 to 3, a force transducer embodying the invention is seen to comprise a flexure beam or element 10 having an immovable portion 12 and a movable portion 14 joined by a flexible portion 16. Flexure element 10 typically is made from a resilient material such as steel in a rectangular parallelepiped configuration, as illus-trated; however, any suitably resilient~material may beused. Flexible portion 16 is formed by drilling or other-wise forming two holes 18,20 laterally through element 10, joining the holes with a slot 22, and opening hole 20 to the bottom of element 10 with a slot 24. Thus, when im-movable portion 12 is fixed and a force is applied to mov-able portion 14 as indicated by the arrow in Figure 1, the upper surface 26 of flexible portion 16 deforms into a curved configuration so that the thin section 28 above hole 18 is placed in tension; and the thin section 30 a~ove hole 20 is placed in compression.
Four thin film strain gage resistance elements Rl, R2, R3 and R4 are deposited on upper surface 26 in a manner to be described below, so that Rl and R3 are above thin section 28 and R2 and R4 are above thin section 30.
Figure 2 indicates schematically which strain gage resis-tance elements are in tension ~T) and compression (C~, and also shows their interconnection into a Wheatstone bridge pattern. Resistance elements Rl and R4 are connected at node 32 by thin film metal leads 34,36. A long thin film lead 38 runs from node 32 off movable portion 14, onto im-movable portion 12 and to a serpentine thin film temperature compensation resistance element RSl which is of the same metal as lead 38. The other end of resistance element Rsl joins a connector pad 40. A thin film lead 42 runs from re-sistance element R4 off movable portion 14, onto immovableportion 12 and to a serpentine thin film temperature compen-~D-7073 sation resistance element Rzl which also is of the same metal as lead 42. The other end of resistance element Rzl joins a second of connector pads 44. Resistance elements Rl and R2 are connected at node 46 by thin film metal leads 48,50.
A long thin film lead 52 runs from node 46 to a connector pad 54 deposited on immovable portion lZ. A thin film lead 56 runs from resistance element R2 to node 58 which is connec-ted~to resistance element R3 by thin film lead 60. A long thin film lead 62 runs from node 58 to a further serpentine thin film temperature compensation resistance element RS2 deposited on immovable portion 12. The other end of resis-tance element Rs2 joins a connector pad 64. Finally, a long thin film lead 66 runs from resistance element R3 to a fur-ther serpentine thin film temperAture compensation resistance element R 2 deposited on immovable portion 12 and formed of the same metal as lead 66. Resistance element Rz2 terminates at a second of connector pads 68.
In Figure 3, a schematic sectional view is shown, taken along line 3-3 of Figure 1, next to resistance element Rl. Resistance elements Rl to R4 and elements 32 to 68 preferably are deposited on flexure element 12 using a unique four layer structure and conventional photolithographic tech-niques to define resistor and lead geometries. Following suit-~ble cleaning of flexure element 12, an electrically insula-tive layer 70, a resistive layer 72 and a conductive layer 74 are deposited seriatim on surface 26, so that the entire surface 26 is covered by three congruent layers. Then, using a suitable photomask, layer 74 is etched away to leave behind only those portions of layer 74 re~uired for the lead pattern and temperature compensation resistance geometries discussed above. After th~t, using another suitable photomask, layer 72 is etched away to leave behind only resistance elements Rl, R2, R3 and R4 joined to their respective leads. As shown in Figure 3, each lead and temperature compensation resistance element actually is made up of two superposed thin films of congruent geometry, an upper metal film remaining from layer 74 and beneath it a lower resistive film remainlng from layer 72.
A passivatio~ layer 76 preferably is applied over the entire - gage assembly, followqng which through holes or vias (not shown), S are etched through to connector pads 40, 44 (2) 54, 64 and 68 (2).
Insulative layer 70 may be formed of ~ 05; resistive layer 72, of oonventional cermet material; and conductive layer 74, of gold. Other suitable materials may also e used such as alumina or Fosterite (a trade mark for a magnesium-silicon-oxygen - 10 insulating mater;~l) for insulative layer 70; Nichr e, (a trade mark for a nickel-iron-chromium alloy) MOSI or CRSI, for resistive layer 72; and nickel, for conductive layer 74. The temperature ccefficient of resistance of the strain gage resistive material 72 is chosen to be of opposite polarity to that of the lead material 74.
In operation, as movable portion 14 is deflecte~ upwardly due to applied force, the resistance of elements Rl to Rg will change due to the applied strain. Bridge power is applied across connector pads 40,64 and the bridge output is taken across connector pads 54 and 44-68, in the well known manner. Should the temperature of the various resistances change from the level at which the transducer was calibrated, the resistance of elements Rl to R4 will chan~e in one direction; and that of elements Rsl and Rs2 and the elements of R 1 and/or Rz2 (left in the circuit) will change in the opposite direction. The determuning factor of whether Rzl and Rz2 are left in the circuit or shorted out of the circuit during calibration depends on the zero setting cali-bration requirements. The changes in resistance Rsl and Rs2 `.~
6~6~9 tend to maintain a relatively constant span or gaye factor;
whereas, the changes in Rzl and/or Rz2 tend to maintain a relatively constant zero setting when no load is applied, even as temperature varies.
Resistances Rsl and RS2 are shown in the input cir-cuit to the bridge; however, placing them in the output cir-cuit is also within the scope of the invention. Similarly, resis'cances Rzl and Rz~ are shown in series with the strain gage resistances in the legs of the bridgei but they could 13 also be placed in parallel with the strain gage resistances and still be within the scope of the invention. Also, while serpentine geometries are shown for the temperature compensa-tion resistances, this geometry is not critical, other ar-rangements being encompassed by the invention. For example, variation of the thickness of the gold layer to affect the compensation resistances is an alternate approach.
Having described my invention in sufficient detail to enable those skilled in the art to make and use it, I
claim:
.. .. . .. . .
This invention relates to a thin film strain gage apparatus.
Force transducers embodying thin film strain gaga resistance bridges have been in use for many years. Typical-ly, the gages are provided on a flexure element which deforms in response to an applied force. In such cases, temperature effects may cause unequal expansion of the legs of the bridge even when no actual force is being applied. This cau-ses a shift in the zero point of the bridge since an output will be produced even when no force is applied. Similarly, temperature effects may result in differential changes in the elasticity or spring constant of various parts of the trans-ducer, so that a given deflection of the flexure element will cause different bridge outputs as the temperature varies.
This causes a shift in the span of the bridge, also known as the gage factor or sensitivity.
Various approaches to compensation for temperature effects have been followed in the past. Bodner et al dis-closed in U.S. Patent 2,930,224 a type of temperature compen-sating strain gage in which a strain-insensitive thermocouple is used to generate a current flow opposite to that flowing in the gage resistance in order to cancel out temperature ef-fects. The temperature compensating elements, however, are lo-cated on the strained portion of the flexure element and there-fore in fact are subject to resistanoe variations due to applied strain.
Starr also disclosed in U.S. Patent 3,034,346 a technique for ~k ~D-7073 ~ rl¢~ ~z~
compensation of strain gage nonlinearity in which the compen-sating resistances are placed on the strained portion of the flexure element. Billette et al show in U.S. Patent No.
3,886,799 a type of semiconductor pressure transducer in which compensating elements are provided on the flexure element with the strain gage bridge.
While these prior art devices have achieved a mea-sure of success in compensating for temperature effects, the location of the compensating elements on the strained portion of the flexure element causes resistance variations due to strain which tend to interfere with the desired function of the compensating elements: the minimization of temperature effects. Moreover, due to the complicated procedures by which prior art thin film strain gage transducers have been made, manufacturing time has been rather long and cost high.
OBJECTS OF THE INVENTION
An object of the invention is to provide an improved thin film strain gage transducer havin~ provision for tempera-ture compensation.
Another object of the invention is to provide such a transducer in which the compensating elements are not subject ta applied strain which would influence their performance.
Still another object of the invention is to provide such a transducer in which the structure of the strain gages and compensating elements is quite simple, thereby facilitat-ing quick and less expensive manufacture.
These objects are given only by way of example;
thus, other desirable objectives and advantages inherently achieved by the disclosed invention may occur to those skilled in the art. Nonetheless, the scope of protection is to be limited only by the appended claims.
SUMMARY OF THE INVENTION
The above objects and other advantages are achieved with the invention which comprises, in one embodiment, a flexure element having at least one thin film strain gage 3~
resistance element deposited thereon in a position to be strained upon deformation of the flexure element. Leads of a material having a temperature coefficient of resistance opposite to that of the strain gage resistances are attached to the gages. Temperature compensation resistors are f~rmed in the leads and deposited at a location on the flexure ele-ment which is unstrained during operation. A bridge of the strain gages is usually used. Due to the simplified process used to make the transducer, the leads are superposed on an underlying thin layer of the same material as the strain gage resistances.
As used in this application, the term "thin film"
refers to elements of minute thickness which are deposited using sputtering or vacuum deposition techniques. The thick-ness of such films is typically measured in Angstrom unitsor microns so that several layers of such "thin films" may have a thickness of only 4 to 30 microns and an individual layer may have a thickness of about 200 Angstrom units to 1 micron. Such thin film elements are used in integrated cir-cuits and are readily distinguishable from discrete elementsor, as in the case of strain gages, from bonded gages or wire gages.
BRIEF DESCRIPTION OF THE DRAWING
-Figure 1 shows a greatly enlarged, perspective view of a flexure element having deposited thereon a temperature compensated strain gage bridge according to the present in-vention.
Figure 2 shows a schematic diagram of the bridge illustrated in Figure 1.
Figure 3 shows a greatly enlarged cross-section taken along line 3-3 in Figure 1, indicating portions of the individual thin films deposited to form the bridge strain gage resistances and electrical leads.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The following is a detailed description of the . .
6~
invention, reference being made to the drawing in which like reference numerals identify like elements of structure in each of the several Figures.
Referring to Figures 1 to 3, a force transducer embodying the invention is seen to comprise a flexure beam or element 10 having an immovable portion 12 and a movable portion 14 joined by a flexible portion 16. Flexure element 10 typically is made from a resilient material such as steel in a rectangular parallelepiped configuration, as illus-trated; however, any suitably resilient~material may beused. Flexible portion 16 is formed by drilling or other-wise forming two holes 18,20 laterally through element 10, joining the holes with a slot 22, and opening hole 20 to the bottom of element 10 with a slot 24. Thus, when im-movable portion 12 is fixed and a force is applied to mov-able portion 14 as indicated by the arrow in Figure 1, the upper surface 26 of flexible portion 16 deforms into a curved configuration so that the thin section 28 above hole 18 is placed in tension; and the thin section 30 a~ove hole 20 is placed in compression.
Four thin film strain gage resistance elements Rl, R2, R3 and R4 are deposited on upper surface 26 in a manner to be described below, so that Rl and R3 are above thin section 28 and R2 and R4 are above thin section 30.
Figure 2 indicates schematically which strain gage resis-tance elements are in tension ~T) and compression (C~, and also shows their interconnection into a Wheatstone bridge pattern. Resistance elements Rl and R4 are connected at node 32 by thin film metal leads 34,36. A long thin film lead 38 runs from node 32 off movable portion 14, onto im-movable portion 12 and to a serpentine thin film temperature compensation resistance element RSl which is of the same metal as lead 38. The other end of resistance element Rsl joins a connector pad 40. A thin film lead 42 runs from re-sistance element R4 off movable portion 14, onto immovableportion 12 and to a serpentine thin film temperature compen-~D-7073 sation resistance element Rzl which also is of the same metal as lead 42. The other end of resistance element Rzl joins a second of connector pads 44. Resistance elements Rl and R2 are connected at node 46 by thin film metal leads 48,50.
A long thin film lead 52 runs from node 46 to a connector pad 54 deposited on immovable portion lZ. A thin film lead 56 runs from resistance element R2 to node 58 which is connec-ted~to resistance element R3 by thin film lead 60. A long thin film lead 62 runs from node 58 to a further serpentine thin film temperature compensation resistance element RS2 deposited on immovable portion 12. The other end of resis-tance element Rs2 joins a connector pad 64. Finally, a long thin film lead 66 runs from resistance element R3 to a fur-ther serpentine thin film temperAture compensation resistance element R 2 deposited on immovable portion 12 and formed of the same metal as lead 66. Resistance element Rz2 terminates at a second of connector pads 68.
In Figure 3, a schematic sectional view is shown, taken along line 3-3 of Figure 1, next to resistance element Rl. Resistance elements Rl to R4 and elements 32 to 68 preferably are deposited on flexure element 12 using a unique four layer structure and conventional photolithographic tech-niques to define resistor and lead geometries. Following suit-~ble cleaning of flexure element 12, an electrically insula-tive layer 70, a resistive layer 72 and a conductive layer 74 are deposited seriatim on surface 26, so that the entire surface 26 is covered by three congruent layers. Then, using a suitable photomask, layer 74 is etched away to leave behind only those portions of layer 74 re~uired for the lead pattern and temperature compensation resistance geometries discussed above. After th~t, using another suitable photomask, layer 72 is etched away to leave behind only resistance elements Rl, R2, R3 and R4 joined to their respective leads. As shown in Figure 3, each lead and temperature compensation resistance element actually is made up of two superposed thin films of congruent geometry, an upper metal film remaining from layer 74 and beneath it a lower resistive film remainlng from layer 72.
A passivatio~ layer 76 preferably is applied over the entire - gage assembly, followqng which through holes or vias (not shown), S are etched through to connector pads 40, 44 (2) 54, 64 and 68 (2).
Insulative layer 70 may be formed of ~ 05; resistive layer 72, of oonventional cermet material; and conductive layer 74, of gold. Other suitable materials may also e used such as alumina or Fosterite (a trade mark for a magnesium-silicon-oxygen - 10 insulating mater;~l) for insulative layer 70; Nichr e, (a trade mark for a nickel-iron-chromium alloy) MOSI or CRSI, for resistive layer 72; and nickel, for conductive layer 74. The temperature ccefficient of resistance of the strain gage resistive material 72 is chosen to be of opposite polarity to that of the lead material 74.
In operation, as movable portion 14 is deflecte~ upwardly due to applied force, the resistance of elements Rl to Rg will change due to the applied strain. Bridge power is applied across connector pads 40,64 and the bridge output is taken across connector pads 54 and 44-68, in the well known manner. Should the temperature of the various resistances change from the level at which the transducer was calibrated, the resistance of elements Rl to R4 will chan~e in one direction; and that of elements Rsl and Rs2 and the elements of R 1 and/or Rz2 (left in the circuit) will change in the opposite direction. The determuning factor of whether Rzl and Rz2 are left in the circuit or shorted out of the circuit during calibration depends on the zero setting cali-bration requirements. The changes in resistance Rsl and Rs2 `.~
6~6~9 tend to maintain a relatively constant span or gaye factor;
whereas, the changes in Rzl and/or Rz2 tend to maintain a relatively constant zero setting when no load is applied, even as temperature varies.
Resistances Rsl and RS2 are shown in the input cir-cuit to the bridge; however, placing them in the output cir-cuit is also within the scope of the invention. Similarly, resis'cances Rzl and Rz~ are shown in series with the strain gage resistances in the legs of the bridgei but they could 13 also be placed in parallel with the strain gage resistances and still be within the scope of the invention. Also, while serpentine geometries are shown for the temperature compensa-tion resistances, this geometry is not critical, other ar-rangements being encompassed by the invention. For example, variation of the thickness of the gold layer to affect the compensation resistances is an alternate approach.
Having described my invention in sufficient detail to enable those skilled in the art to make and use it, I
claim:
.. .. . .. . .
Claims (8)
1. An improved thin film strain gage transducer, comprising:
a flexure element deformable in response to an applied force;
at least one thin film strain gage resistance element deposited on said flexure element in a position to be strained upon deformation of æaid flexure element, said strain gage re-sistance element being made from a first material having a first temperature coefficient of resistance;
at least two electrically conductive thin film leads de-posited on said flexure element and connected to said at least one thin film strain gage resistance element for the purpose of conducting current to and from said resistance element, said thin film leads being made from a second material hav-ing a second temperature coefficient of resistance opposite in algebraic sign to that of said first material; and at least one thin film temperature compensation resis-tance element deposited on said flexure element, connected in circuit with said leads and located in a position on said flexure element not subject to strain upon deformation of said flexure element, said temperature compensation ele-ment also being made from said second material, whereby changes in resistance of said strain gage resistance element due to temperature variations are offset by opposite changes in resistance of said temperature compensation resistance element thus rendering the transducer less sensitive to var-iations in ambient temperature.
a flexure element deformable in response to an applied force;
at least one thin film strain gage resistance element deposited on said flexure element in a position to be strained upon deformation of æaid flexure element, said strain gage re-sistance element being made from a first material having a first temperature coefficient of resistance;
at least two electrically conductive thin film leads de-posited on said flexure element and connected to said at least one thin film strain gage resistance element for the purpose of conducting current to and from said resistance element, said thin film leads being made from a second material hav-ing a second temperature coefficient of resistance opposite in algebraic sign to that of said first material; and at least one thin film temperature compensation resis-tance element deposited on said flexure element, connected in circuit with said leads and located in a position on said flexure element not subject to strain upon deformation of said flexure element, said temperature compensation ele-ment also being made from said second material, whereby changes in resistance of said strain gage resistance element due to temperature variations are offset by opposite changes in resistance of said temperature compensation resistance element thus rendering the transducer less sensitive to var-iations in ambient temperature.
2. A transducer according to Claim 1, wherein there are at least four of said strain gage resistance ele-ments connected in a Wheatstone bridge configuration; and said at least one thin film temperature compensation resis-tance is connected in the input power circuit of said bridge to provide temperature compensation of the span or gage factor of said bridge.
3. A transducer according to Claim 1, wherein there are at least four of said strain gage resistance ele-ments connected in a Wheatstone bridge configuration; and said at least one thin film temperature compensation resis-tance is connected in at least one leg of said bridge to provide temperature compensation of the zero setting of said bridge.
4. A transducer according to Claim 1, further comprising a thin film of electrical insulator material de-posited on said flexure element beneath said at least one thin film strain gage resistance element, and a thin film of said first material deposited on said electrical insulator material beneath said thin film leads.
5. A transducer according to Claim 2, wherein another thin film temperature compensation resistance is con-nected in at least one leg of said bridge to provide tempera-ture compensation of the zero setting of said bridge.
6. A transducer according to Claim 2, further com-prising a thin film of electrical insulator material de-posited on said flexure element beneath said at least one thin film strain gage resistance element, and a thin film of said first material deposited on said electrical insulator material beneath said thin film leads.
7. A transducer according to Claim 3, further comprising a thin film of electrical insulator material de-posited on said flexure element beneath said at least one thin film strain gage resistance element, and a thin film of said first material deposited on said electrical insulator material beneath said thin film leads.
8. A transducer according to Claim 5, further comprising a thin film of electrical insulator material de-posited on said flexure element beneath said at least one thin film strain gage resistance element, and a thin film of said first material deposited on said electrical insulator material beneath said thin film leads.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000364337A CA1149629A (en) | 1980-11-10 | 1980-11-10 | Thin film strain gage with unstrained temperature compensation resistances |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000364337A CA1149629A (en) | 1980-11-10 | 1980-11-10 | Thin film strain gage with unstrained temperature compensation resistances |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1149629A true CA1149629A (en) | 1983-07-12 |
Family
ID=4118402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000364337A Expired CA1149629A (en) | 1980-11-10 | 1980-11-10 | Thin film strain gage with unstrained temperature compensation resistances |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1149629A (en) |
-
1980
- 1980-11-10 CA CA000364337A patent/CA1149629A/en not_active Expired
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| MKEX | Expiry |