GB2225433A - Capacitive-effect acceleration transducer - Google Patents
Capacitive-effect acceleration transducer Download PDFInfo
- Publication number
- GB2225433A GB2225433A GB8926379A GB8926379A GB2225433A GB 2225433 A GB2225433 A GB 2225433A GB 8926379 A GB8926379 A GB 8926379A GB 8926379 A GB8926379 A GB 8926379A GB 2225433 A GB2225433 A GB 2225433A
- Authority
- GB
- United Kingdom
- Prior art keywords
- blade
- capacitor
- acceleration
- fixed
- transducer according
- 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
- 230000001133 acceleration Effects 0.000 title claims abstract description 21
- 239000002184 metal Substances 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 18
- 239000003990 capacitor Substances 0.000 claims abstract description 15
- 239000012777 electrically insulating material Substances 0.000 claims description 3
- 239000004020 conductor Substances 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 abstract description 2
- 239000011810 insulating material Substances 0.000 abstract 1
- 239000000919 ceramic Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- JUWSSMXCCAMYGX-UHFFFAOYSA-N gold platinum Chemical compound [Pt].[Au] JUWSSMXCCAMYGX-UHFFFAOYSA-N 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- SWELZOZIOHGSPA-UHFFFAOYSA-N palladium silver Chemical compound [Pd].[Ag] SWELZOZIOHGSPA-UHFFFAOYSA-N 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
- G01P2015/0805—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration
- G01P2015/0822—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass
- G01P2015/0825—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass
- G01P2015/0828—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values being provided with a particular type of spring-mass-system for defining the displacement of a seismic mass due to an external acceleration for defining out-of-plane movement of the mass for one single degree of freedom of movement of the mass the mass being of the paddle type being suspended at one of its longitudinal ends
Abstract
The transducer includes a support plate 2 and a support 4 to which is cantilevered a flexible metal blade 6 which faces and is spaced from a fixed metal plate member 3 so as to constitute a capacitor whose capacitance is variable in dependence on the acceleration to which it is subjected. The support plate 2 is of insulating material and plate 3 may be a deposited thin metal layer, or may comprise a second metal blade also cantilevered from support 4. Detector means are provided for producing an electrical signal indicative of the capacitance of the capacitor and hence of the acceleration. The capacitor may either affect the frequency of an oscillator with subsequent voltage to frequency conversion or a fixed oscillator may be connected to a monostable with pulse duration controlled by the capacitor. <IMAGE>
Description
DESCRIPTION '1A capacitive-effect acceleration transducer"
The present invention relates to a capacitive-effect acceleration transducer, characterised in that it includes in combination: - a support structure which is intended to be fixed to the body whose acceleration is to be detected7 - a metal plate member carried by the support, - a flexible metal blade having a first end by which it is cantilevered from the support structure and a second end facing and spaced from the plate member in the direction in which the acceleration is to be detected, so as to constitute therewith a capacitor whose capacitance has a predetermined value at rest and is variable in dependence on the acceleration of the body in the said direction, and - detector means for providing an electrical signal indicative of the capacitance of the capacitor.
By virtue of these characteristics, the transducer is simple, precise and reliable.
The invention will now be described in detail with reference to the appended drawings, provided purely by way of non-limiting example, in which:
Figure 1 is a perspective view of an acceleration transducer according to the present invention,
Figure 2 is a view taken on the arrow II of Figure 1,
Figures 3, 4 and 5 are perspective views showing three alternative embodiments of the transducer according to the invention,
Figure 6 is a view taken on the arrow VI of Figure 4,
Figure 7 is a section taken on the line Vil-Vil of
Figure 5, and
Figure 8 is a block diagram showing the operation of an electronic circuit associated with the transducer according to the invention.
In the drawings, a capacitive-effect acceleration transducer is indicated 1. With reference to Figures 1 and 2, the transducer includes a support plate 2 of electrically insulating material which is intended to be fixed to the surface of the body (not shown) whose acceleration is to be detected. A plate member 3 constituted by a metal block and a support 4 whose thickness is slightly greater than that of the block 3 are fixed to the plate 2. The transducer 1 also includes a flexible metal blade 5, for example of string steel, having a first end 6 by which it is cantilevered from the support 4 and a second end 7 facing and spaced from the upper surface of the block 3. The end 7 of the blade 5 and the plate member 3 thus define a capacitor which has a predetermined value at rest.A mass 8 is provided at the end 7 of the blade 5 and is fixed to the opposite surface of the blade from the plate member 3.
When the transducer 1 is subjected to an acceleration in a direction perpendicular to the plate member 3 and the blade 5, that is, parallel with the line shown by the double arrow A in the drawings, the mass 8 is subjected to a force which causes the free end 7 of the blade to oscillate. This oscillation causes a variation in the capacitance of the capacitor defined by the plate member 3 and the blade 5. This variation in capacitance is detected by an electronic circuit, which will be described further below, to which the plate member 3 and the blade 5 are connected by means of two electrical conductors 9.
In the variant illustrated in Figure 3, the fixed plate member 3 is replaced by a second flexible blade 10 cantilevered from the support 4 to which the first blade 5 is fixed. The two blades 5 and 10 are kept apart by a layer 11 of electrically-insulating material. A mass 12 which, like the mass 8 fixed to the first blade 5, is sensitive to acceleration in the direction indicated by the double arrow A, is also fixed to the free end of the second blade 10.
In the embodiment shown in Figures 4 and 6, the support plate 2 is made of ceramics. The fixed plate member 3 is constituted by a thin metal layer deposited on the surface of the ceramic plate 2 by silk-screen printing, drying and baking. The material constituting the metal deposits is, for example, platinum-gold or palladium-silver. The flexible blade 5 may be of brass, in which case it can be soldered with tin to a metal layer 15 deposited on the ceramic plate 2. In this case, the thickness of the material added by the soldering also serves to keep the plate member 3 and the flexible blade 5 apart. Alternatively, the blade 5 can be glued to the support plate 2 and in this case it is necessary to establish an electrical connection between the blade 5 and the metal layer 15, as indicated by broken lines 16 in Figures 4 to 6.
According to a further variant shown in Figures 5 to 7, a printed circuit 18 can be used as the support plate and, in this case, the fixed , plate member is constituted by a metal layer 19 of the circuit. The flexible blade 5 is fixed to the printed circuit 18 by means of screws 20, with the interposition of a metal spacer 21. The spacer 21 connects the blade 5 electrically to a metal layer 22 of the printed circuit. The layers 18 and 22 are connected electrically to the components of an electronic circuit provided on the printed circuit 18.
Figure 8 shows a block diagram of an electronic detection circuit associated with the transducer 1.
According to a first embodiment, the capacitor constituted by the transducer 1 is connected to an oscillator 25 whose frequency depends on the capacitance of the capacitor. The signal output by the oscillator 25 is sent to a monostable circuit 26 and then te a low-pass filter 27. A frequency-voltage conversion is thus achieved. The voltage signal V output by the filter 27 is thus indicative of the value of the capacitance of the transducer 1 and hence of the acceleration to which the latter is subjected.
Alternatively, the oscillator 25 may work at a fixed frequency, whilst the transducer 1 is connected to the monostable circuit 26, as shown by the broken lines in
Figure 8. The duration of the signal of the monostable circuit 26 is thus modulated and, as in the previous case, the output signal V obtained is proportional to the value of the acceleration to which the transducer 1 is subjected.
Claims (10)
1. A capacitive-effect acceleration transducer, characterised in that it includes in combination: - a support structure which is intended to be fixed to the body whose acceleration is to be detected, - a metal plate member carried by the support, - a flexible metal blade having a first end by which it is cantilevered from the support structure and a second end facing and spaced from the plate member so as to constitute therewith a capacitor whose capacitance has a predetermined value at rest and is variable in dependence on the acceleration of the body in the direction , and - detector means for providing an electrical signal indicative of the capacitance of the capacitor.
2. A transducer according to Claim 1, characterised in that the plate member is fixed and is carried by the support structure.
3. A transducer according to Claim 1, characterised in that the plate member is constituted by a second flexible metal blade also having a first end by which it is cantilevered from the support structure and its other end facing and spaced from the first blade.
4. A transducer according to any one of the preceding claims, characterised in that a mass is fixed to the first blade and is subject to the action of the acceleration to be detected in use.
5. A transducer according to Claims 3 and 4, characterised in that a mass is also fixed to the second blade and is subject to the action of the acceleration to be detected in use.
6. A transducer according to Claim 5, characterised in that the masses associated with the first blade and and with the second blade are fixed to those surfaces of the blades which do not face each other.
7. A transducer according to Claim 2, characterised in that the plate member is constituted by a layer of conductive material deposited on a support base of electrically-insulating material.
8. A transducer according to any one of the preceding claims, characterised in that the detector means comprise an electronic circuit including an oscillator
whose frequency depends on the capacitance of the capacitor) and a frequency-voltage converter
connected to the output of the oscillator,
9. A transducer according to any one of Claims 1 to 7, characterised in that an electronic circuit is associated with the capacitor and includes a fixed-frequency oscillator and a monostable circuit whose input is connected to the output of the oscillator the monostable circuit being adapted to output a pulse whose duration depends on the capacitance of the capacitor
10. A capacitative-effect acceleration transducer substantially as hereinbefore described with reference to
Figures 1 and 2, or Figure 3, or Figures 4 and 6 or
Figures 5 and 7, together with Figure 8 of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT68046/88A IT1223933B (en) | 1988-11-23 | 1988-11-23 | CAPACITIVE ACCELERATION TRANSDUCER |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8926379D0 GB8926379D0 (en) | 1990-01-10 |
| GB2225433A true GB2225433A (en) | 1990-05-30 |
| GB2225433B GB2225433B (en) | 1993-01-27 |
Family
ID=11307438
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8926379A Expired - Fee Related GB2225433B (en) | 1988-11-23 | 1989-11-22 | A capacitive-effect acceleration transducer |
Country Status (5)
| Country | Link |
|---|---|
| DE (1) | DE8913756U1 (en) |
| ES (1) | ES1012120Y (en) |
| FR (1) | FR2639435B3 (en) |
| GB (1) | GB2225433B (en) |
| IT (1) | IT1223933B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5128581A (en) * | 1989-05-02 | 1992-07-07 | Fujikura Ltd. | Piezoelectric acceleration sensor and piezoelectric acceleration sensor device |
| US5438859A (en) * | 1991-09-24 | 1995-08-08 | Murata Manufacturing Co. Ltd. | Acceleration sensor having fault diagnosing device |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5239871A (en) * | 1990-12-17 | 1993-08-31 | Texas Instruments Incorporated | Capacitive accelerometer |
| DE4244560A1 (en) * | 1992-12-30 | 1994-07-07 | Akebono Brake Ind | Acceleration detection method providing 2-dimensional acceleration measurements |
| US5555766A (en) * | 1993-11-04 | 1996-09-17 | Texas Instruments Incorporated | Acceleration sensor apparatus and method for making same |
| DE10053309B4 (en) * | 2000-10-27 | 2005-02-24 | Eads Deutschland Gmbh | Micromechanical acceleration sensor |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1303025A (en) * | 1970-11-12 | 1973-01-17 | ||
| WO1987007729A1 (en) * | 1986-06-10 | 1987-12-17 | Metravib R.D.S. | Silicon-integrated pick-up for measuring mechanical magnitudes, and method of fabrication |
| US4736629A (en) * | 1985-12-20 | 1988-04-12 | Silicon Designs, Inc. | Micro-miniature accelerometer |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4951510A (en) * | 1988-07-14 | 1990-08-28 | University Of Hawaii | Multidimensional force sensor |
-
1988
- 1988-11-23 IT IT68046/88A patent/IT1223933B/en active
-
1989
- 1989-11-21 DE DE8913756U patent/DE8913756U1/de not_active Expired - Lifetime
- 1989-11-22 GB GB8926379A patent/GB2225433B/en not_active Expired - Fee Related
- 1989-11-22 ES ES19898903507U patent/ES1012120Y/en not_active Expired - Lifetime
- 1989-11-22 FR FR898915324A patent/FR2639435B3/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1303025A (en) * | 1970-11-12 | 1973-01-17 | ||
| US4736629A (en) * | 1985-12-20 | 1988-04-12 | Silicon Designs, Inc. | Micro-miniature accelerometer |
| WO1987007729A1 (en) * | 1986-06-10 | 1987-12-17 | Metravib R.D.S. | Silicon-integrated pick-up for measuring mechanical magnitudes, and method of fabrication |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5128581A (en) * | 1989-05-02 | 1992-07-07 | Fujikura Ltd. | Piezoelectric acceleration sensor and piezoelectric acceleration sensor device |
| US5438859A (en) * | 1991-09-24 | 1995-08-08 | Murata Manufacturing Co. Ltd. | Acceleration sensor having fault diagnosing device |
| US5517845A (en) * | 1991-09-24 | 1996-05-21 | Murata Manufacturing Co., Ltd. | Acceleration sensor having fault diagnosing device |
Also Published As
| Publication number | Publication date |
|---|---|
| ES1012120Y (en) | 1991-01-01 |
| GB2225433B (en) | 1993-01-27 |
| DE8913756U1 (en) | 1990-01-11 |
| GB8926379D0 (en) | 1990-01-10 |
| IT1223933B (en) | 1990-09-29 |
| ES1012120U (en) | 1990-07-01 |
| FR2639435B3 (en) | 1990-10-12 |
| IT8868046A0 (en) | 1988-11-23 |
| FR2639435A3 (en) | 1990-05-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19991122 |