GB2248113A - An electrical measuring arrangement with temperature compensation - Google Patents
An electrical measuring arrangement with temperature compensation Download PDFInfo
- Publication number
- GB2248113A GB2248113A GB9114763A GB9114763A GB2248113A GB 2248113 A GB2248113 A GB 2248113A GB 9114763 A GB9114763 A GB 9114763A GB 9114763 A GB9114763 A GB 9114763A GB 2248113 A GB2248113 A GB 2248113A
- Authority
- GB
- United Kingdom
- Prior art keywords
- temperature
- signal
- resistors
- bridge
- sensor
- 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.)
- Withdrawn
Links
- 230000001419 dependent effect Effects 0.000 claims abstract 2
- 238000000034 method Methods 0.000 claims description 2
- 239000000758 substrate Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
- B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
- B60R21/013—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over
- B60R21/0132—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over responsive to vehicle motion parameters, e.g. to vehicle longitudinal or transversal deceleration or speed value
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
- B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
- B60R21/013—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over
- B60R21/0136—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting collisions, impending collisions or roll-over responsive to actual contact with an obstacle, e.g. to vehicle deformation, bumper displacement or bumper velocity relative to the vehicle
-
- 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
- G01P15/0891—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 with indication of predetermined acceleration values
-
- 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
- G01P15/12—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 alteration of electrical resistance
- G01P15/123—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 alteration of electrical resistance by piezo-resistive elements, e.g. semiconductor strain gauges
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2400/00—Indexing codes relating to detected, measured or calculated conditions or factors
- B60G2400/10—Acceleration; Deceleration
- B60G2400/106—Acceleration; Deceleration longitudinal with regard to vehicle, e.g. braking
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2400/00—Indexing codes relating to detected, measured or calculated conditions or factors
- B60G2400/80—Exterior conditions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2600/00—Indexing codes relating to particular elements, systems or processes used on suspension systems or suspension control systems
- B60G2600/08—Failure or malfunction detecting means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60G—VEHICLE SUSPENSION ARRANGEMENTS
- B60G2800/00—Indexing codes relating to the type of movement or to the condition of the vehicle and to the end result to be achieved by the control action
- B60G2800/22—Braking, stopping
- B60G2800/222—Braking, stopping during collision
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Air Bags (AREA)
- Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
Abstract
To provide temperature compensation in a 'Wheatstone' bridge which includes piezo-resistors (R3, R4), a temperature-dependent signal is derived from the bridge itself and fed to a processing circuit (8) together with the bridge output voltage US. As described the arrangement measures declaration of a vehicle and is used to trigger an air-bag (11). The temperature signal may be taken off across a resistor (R5) which carries the bridge supply current since the current varies with the temperature of the resistors (R3, R4). Alternatively the temperature signal is taken from one of the piezo-resistors by use of a switching circuit (Fig. 3 not shown). <IMAGE>
Description
DESCRIPTION OF INVENTION "An Electrical Arrangement"
THE PRESENT INVENTION relates to an electrical arrangement and more particularly relates to a sensor and a temperature compensation device.
The invention will be described with reference to a sensor which is used to trigger a safety device in a motor vehicle in the event that the vehicle is involved in an accident such as, for example, an air-bag. Such an airbag may be provided at an appropriate position within a motor vehicle and may be adapted to be inflated in response to a signal from the sensor to provide a "cushion" to protect a person travelling in the vehicle.
According to one aspect of this invention there is provided a sensor, said sensor comprising one or more electric resistors, means to provide electric power to the resistors, and means to derive an electric output from the resistors, the output being a function of the mechanical stress applied to the sensor, means being provided to derive a signal indicative of temperature from a current passing through at least one of the said one or more resistors, said signal being supplied to a signal processing means adapted to process the output signal, the signal processing means being adapted to compensate the output signal for temperature.
Preferably said one or more resistors are in the form of a "wheatstone" bridge.
Advantageously the said temperature signal is derived from one transistor by applying current to the resistor.
Preferably switch means are provided to isolate the resistor from the rest of the bridge when the said current is passed through the resistor.
Advantageously the said temperature signal is derived from a current flowing through the whole bridge and through a further resistor which has a resistance which is substantially temperature independent.
In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which
FIGURE 1 illustrates part of a sensor adapted to be mounted in a motor vehicle to sense deceleration of the vehicle,
FIGURE 2 illustrates part of an electric circuit incorporating the sensor components of Figure 1, and
FIGURE 3 illustrates part of an alternative circuit incorporating the components of Figure 1.
Referring now to the drawings, Figure 1 illustrates the operative part of a sensor. From a fixed part 1 of a motor vehicle a flexible substrate 2 depends, the substrate 2 carrying, at its lower end, a weight 3. the substrate 2 is formed of an insulating material. Formed on two opposed sides of the substrate 2 are two Piezo resistive resistances R3 and R4.
A Piezo resistive resistance is a resistance in which the absolute value of the resistance varies in response to mechanical pressures or forces applied to the resistance.
It can P seen that if the arrangement illustrated in Figure 1 is motet on a motor vehicle which is travelling in the direction of the arrow A shown in
Figure 1 and the vehicle suddenly stops the weight 3 will, due to its inertia, continue to travel to the right whereas the fixed part of the vehicle 1 will have stopped.
Consequently the substrate 2 will flex serving to compress the resistance R4 and extend the resistance R3. The absolute value of the resistances R3 and R4 will thus vary.
As can be seen from Figure 2 the resistances R3 and
R4 form part of a "wheatstone" bridge together with other resistors R1 and R2. A voltage is applied across the "wheatstone" bridge by applying a potential between the two terminals 5 and 6. The terminal 5 is a point on the bridge and the terminal 6 is connected to the diagonally opposite point on the bridge by a further resistance R5. The applied potential may be 5 volts. An output voltage US is provided at the output terminals 7, which are connected to the opposite diagonal of the bridge. The value of this output voltage US depends upon the degree of deformation of the resistances R3 and R4.
The terminals 7 are connected to a signal processor 8. A lead 9 extends from a node between the resistance R5 and the bridge to the signal processing circuit 8.
It can be understood that the degree of deformation of the resistances R3 and R4 will depend upon the degree of flexing of the flexible substrate 2 which in turn depends upon the degree of deceleration of the vehicle.
An advantage of a Piezo resistive sensor of the type described above is that it can measure a continuing deformation, in which the substrate 2 is maintained flexed as a vehicle continues to decelerate. This is in contrast, for example, to a Piezo electric sensor in which a voltage is generated as a consequence of deformation of a Piezo electric element. Such a voltage is sensed at the moment that the element is deformed, and when the voltage has flowed through the associated circuitry it is no longer detectable. Thus, a Piezo electric sensor can only measure repeatedly applied forces and then, in effect, only measure repeatedly applied forces having a frequency down to about 1 Hz. However, as has been explained above, a Piezo resistive sensor can measure a non-varying applied force, that is to say it can measure down to a frequency of O Hz.
As mentioned above a Piezo resistive resistance, such as the resistances R3 and R4 may be formed on a substrate 2 for example, using conventional printed circuit technology. Thus such resistances are relatively cheap to generate.
It is, however, a property of Piezo resistive resistances that the resistance is not only a function of the stress applied, but is a function of temperature. Also the change of resistance for a particular degree of stress is a function of temperature, which means that for any particular stress level the value of the output signal US depends upon the temperature. It is thus necessary to provide temperature compensation.
Whilst the temperature compensation can be achieved by providing a compensating arrangement associated with a temperature sensor in the region of the various resistances which form the "wheatstone" bridge, in the present invention a temperature compensation signal is derived from current flowing through at least one of the resistors forming the bridge.
In the embodiment illustrated in Figure 2 the resistance R5 is selected to be a resistance which has very good temperature characteristics, that is to say a resistance which always has the same resistive value regardless of the temperature of the resistance, within a temperature range encompassing the ordinary operating conditions for the sensor.
Since the resistance R5 has a constant value, the potential present on the lead 9 will depend upon the resistance across the diagonal of the "wheatstone" bridge constituted by the resistance R1, R2, R3 and R4. This in turn depends upon the absolute resistance of the resistors forming the bridge. Consequently if the resistors forming the bridge are subjected to a high temperature and have a relatively high resistance the potential applied to lead 9 will be relatively low, whereas if the resistors are cold and have a low resistance the potential applied to lead 9 will be relatively high.
The arrangement may be calibrated in any appropriate manner, and the signal present on the lead 9 may be used by the signal processing circuit 8 to effect an appropriate temperature compensation to the output signal US, thus providing a compensated signal. The compensated signal may be fed to an appropriate discriminator circuit 10 to activate an air-bag 11.
Figure 3 illustrates a modified embodiment of the invention in which the resistance R5 is omitted. The resistance R4 is connected to the rest of the bridge by two switches 12,13, which can be opened so that the resistance
R4 is isolated from the rest of the bridge. Two switched leads 15,16 extend from the resistance R4 to the signal processing circuit 8.
The switches 12,13 and the switches present in leads 15,16 may be transistor switches or appropriate electro mechanical switches. Under signals provided from the signal processing circuit from time-to-time the switches 12,13 will be opened and the switches in the leads 15,16 will be closed thus enabling the signal processing circuit to apply a current to the resistance R4 to determine the resistance of the resistor in absolute terms. This will provide an indication of the temperature of the resistance. Once the appropriate measurement has been made the switches in the leads 15,16 will be opened and the switches 12,13 will be closed so that the "wheatstone" bridge is again functional.It is to be understood that temperature changes within the sensor only take place at a relatively slow rate, and thus if a temperature compensation signal is derived from the resistance R4 at repeated regular intervals, for example, once every 5 seconds, the signal processing circuit will always have available to it a compensating value which is sufficiently accurate.
It is to be appreciated that in the embodiments of
Figures 2 and 3 a temperature compensating signal is derived, that signal being derived from current flowing through at least one of the resistors which forms the "wheatstone" bridge. Thus, effectively, the sensor element that is used to sense the temperature of the components of the "wheatstone" bride comprises at least one of the components of the "wheatstone" bridge. A very accurate temperature compensation can thus be obtained without there being any risk that a separate temperature sensor is not actually subjected to precisely the same temperature conditions as being experienced by the components to be compensated.
Claims (8)
1. A sensor, said sensor comprising one or more electric resistors, means to provide electric power to the resistors, and means to derive an electric output from the resistors, the output being a function of the mechanical stress applied to the sensor, means being provided to derive a signal indicative of temperature from a current passing through at least one of the said one or more resistors, said signal being supplied to a signal processing means adapted to process the output signal, the signal processing means being adapted to compensate the output signal for temperature.
2. A sensor according to Claim 1 wherein said one or more resistors are in the form of a "wheatstone" bridge.
3. A sensor according to Claim 1 or Claim 2 wherein the said temperature signal is derived from one transistor by applying current to the resistor.
4. A sensor according to Claim 3 as dependent upon
Claim 2 wherein switch means are provided to isolate the resistor from the rest of the bridge when the said current is passed through the resistor.
5. A sensor according to Claim 2 wherein the said temperature signal is derived from a current flowing through the whole bridge and through a further resistor which has a resistance which is substantially temperature independent.
6. A safety device substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.
7. A safety device substantially as herein described with reference to and as shown in Figures 1 and 3 of the accompanying drawings.
8. Any novel feature or combination of features disclosed herein.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19914130547 DE4130547A1 (en) | 1990-09-20 | 1991-09-13 | Electrical measuring sensor with temp. compensation e.g. for air bag |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB909020533A GB9020533D0 (en) | 1990-09-20 | 1990-09-20 | An electrical arrangement |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9114763D0 GB9114763D0 (en) | 1991-08-28 |
| GB2248113A true GB2248113A (en) | 1992-03-25 |
Family
ID=10682484
Family Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB909020533A Pending GB9020533D0 (en) | 1990-09-20 | 1990-09-20 | An electrical arrangement |
| GB9114763A Withdrawn GB2248113A (en) | 1990-09-20 | 1991-07-09 | An electrical measuring arrangement with temperature compensation |
| GB9114766A Expired - Fee Related GB2250345B (en) | 1990-09-20 | 1991-07-09 | A safety apparatus |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB909020533A Pending GB9020533D0 (en) | 1990-09-20 | 1990-09-20 | An electrical arrangement |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9114766A Expired - Fee Related GB2250345B (en) | 1990-09-20 | 1991-07-09 | A safety apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (3) | GB9020533D0 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2360361A (en) * | 2000-03-17 | 2001-09-19 | Ind Dataloggers Ltd | Strain gauge with matching resistors on both surfaces of a substrate |
| GB2372817A (en) * | 2000-10-05 | 2002-09-04 | Ind Dataloggers Ltd | Strain gauge having matching metallic layer patterns on opposite sides of a substrate |
| GB2418989A (en) * | 2004-10-06 | 2006-04-12 | Autoliv Dev | Vehicle deformation crash sensor |
| EP2085270A1 (en) * | 2004-06-11 | 2009-08-05 | Robert Bosch GmbH | Hybrid impact sensor |
| US8480124B2 (en) | 2011-01-18 | 2013-07-09 | Autoliv Asp, Inc. | Seat bolster chamber |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3384753B2 (en) * | 1998-10-15 | 2003-03-10 | タカタ株式会社 | Seat load measuring device |
| DE10005445C2 (en) | 1999-02-08 | 2002-08-14 | Takata Corp | Diagnostic method for a seat load measuring device |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1591620A (en) * | 1976-12-21 | 1981-06-24 | Nat Res Dev | Signal-conditioning circuits |
| US4448078A (en) * | 1982-11-23 | 1984-05-15 | The United States Of America As Represented By The Secretary Of The Air Force | Three-wire static strain gage apparatus |
| GB2165647A (en) * | 1984-08-07 | 1986-04-16 | Hanson Res | Method of conducting measurement using an electro-mechanical transducer |
| US4715003A (en) * | 1984-07-27 | 1987-12-22 | Keller Ag Fur Druckmesstechnik | Method for temperature compensation and measuring circuit therefor |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4198677A (en) * | 1978-01-30 | 1980-04-15 | Exxon Research & Engineering Co. | Method and apparatus for compensating a sensor |
| US4672566A (en) * | 1981-12-01 | 1987-06-09 | Nissan Motor Company, Limited | Device for measuring variable with automatic compensation for offset |
| US4765342A (en) * | 1987-07-27 | 1988-08-23 | Trutek Research, Inc. | Timed drift compensation for rate volume monitor |
| DE3844333A1 (en) * | 1988-12-30 | 1990-07-05 | Bosch Gmbh Robert | METHOD AND DEVICE FOR CORRECTING COMPONENT TOLERANCES IN THE PROCESSING OF SIGNALS |
-
1990
- 1990-09-20 GB GB909020533A patent/GB9020533D0/en active Pending
-
1991
- 1991-07-09 GB GB9114763A patent/GB2248113A/en not_active Withdrawn
- 1991-07-09 GB GB9114766A patent/GB2250345B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1591620A (en) * | 1976-12-21 | 1981-06-24 | Nat Res Dev | Signal-conditioning circuits |
| US4448078A (en) * | 1982-11-23 | 1984-05-15 | The United States Of America As Represented By The Secretary Of The Air Force | Three-wire static strain gage apparatus |
| US4715003A (en) * | 1984-07-27 | 1987-12-22 | Keller Ag Fur Druckmesstechnik | Method for temperature compensation and measuring circuit therefor |
| GB2165647A (en) * | 1984-08-07 | 1986-04-16 | Hanson Res | Method of conducting measurement using an electro-mechanical transducer |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2360361A (en) * | 2000-03-17 | 2001-09-19 | Ind Dataloggers Ltd | Strain gauge with matching resistors on both surfaces of a substrate |
| GB2360361B (en) * | 2000-03-17 | 2004-08-25 | Ind Dataloggers Ltd | Improved strain gauge devices |
| GB2372817A (en) * | 2000-10-05 | 2002-09-04 | Ind Dataloggers Ltd | Strain gauge having matching metallic layer patterns on opposite sides of a substrate |
| EP2085270A1 (en) * | 2004-06-11 | 2009-08-05 | Robert Bosch GmbH | Hybrid impact sensor |
| GB2418989A (en) * | 2004-10-06 | 2006-04-12 | Autoliv Dev | Vehicle deformation crash sensor |
| US7836998B2 (en) | 2004-10-06 | 2010-11-23 | Autoliv Development Ab | Crash sensor |
| US8480124B2 (en) | 2011-01-18 | 2013-07-09 | Autoliv Asp, Inc. | Seat bolster chamber |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2250345A (en) | 1992-06-03 |
| GB9114766D0 (en) | 1991-08-28 |
| GB9020533D0 (en) | 1990-10-31 |
| GB2250345B (en) | 1994-06-22 |
| GB9114763D0 (en) | 1991-08-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |