Compression strain sensor

• US 20080011095A1
• Filed: 07/12/2006
• Published: 01/17/2008
• Est. Priority Date: 07/12/2006
• Status: Active Grant

• Current Assignee: CTS Corporation
• Original Assignee: CTS Corporation
• Inventors: Bloom, Terry R.
• Granted Patent: US 7,441,467 B2
• Time in Patent Office: Days
• US Class Current: 73/819
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress

Abstract

A sensor is disclosed for sensing an applied load. The sensor includes a rigid substrate. A strain sensitive resistor is mounted to the substrate. The resistor has a pair of ends. The resistor has a length and a width that defines an area. A pair of conductors are connected to the end of the resistor. A dielectric layer is mounted over the resistor. A load transfer device is mounted to the dielectric layer. The load transfer device transfers the applied load directly to the strain sensitive resistor such that the resistor is compressed. The resistor changes resistance in response to the applied load.

Claims

1. A sensor for sensing an applied load comprising:

a) a rigid substrate having a first surface and a second surface;

b) a first strain sensitive resistor mounted to the first surface, the first resistor having a first end and a second end, the first resistor having a first length and a first width defining a first area;

c) a first conductor mounted to the first surface and connected to the first end;

d) a second conductor mounted to the second surface and connected to the second end;

e) a dielectric layer mounted over the resistor; and

f) a load transfer device mounted to the dielectric layer, the load transfer device transferring the applied load directly to the first strain sensitive resistor such that the first resistor is compressed, the first resistor being adapted to change resistance in response to the applied load.

2. The sensor according to claim 1, wherein a second strain sensitive resistor is mounted under the dielectric layer and the load transfer device.

3. The sensor according to claim 2, wherein a third and fourth resistor are mounted to the substrate, the third and fourth resistor not being located under the load transfer device.

4. The sensor according to claim 3, wherein the first, second, third and fourth resistors are connected in a wheatstone bridge.

5. The sensor according to claim 1, wherein a support is mounted adjacent the second surface.

6. The sensor according to claim 1, wherein the substrate is ceramic.

7. The sensor according to claim 1, wherein the load transfer device is formed from ceramic and is bonded to the first resistor by the dielectric layer.

8. A sensor comprising:

a) substrate having a first and second surface;

b) at least one resistor mounted to the first surface, the resistor having a length, a width and a height, the length, width and height defining a resistor volume, the resistor having a resistance that varies with an applied load;

c) a pair of terminals attached to opposing sides of the resistor, the terminals providing an electrical connection between the resistor and an external electrical circuit

d) a dielectric layer overlying the resistor;

e) a load transfer device overlying the dielectric layer; and

f) the resistor adapted to be directly pressed on by the load transfer device, the resistor adapted to be uniformly compressed by the applied load such that the resistor volume changes with a change in the applied load, the change in resistor volume generating a change in the resistance of the resistor.

9. The sensor according to claim 8, further comprising two resistors mounted under the load transfer device.

10. The sensor according to claim 9, further comprising two resistors mounted to the first surface of the substrate to the side of the load transfer device.

11. The sensor according to claim 10, wherein the resistors are connected to form a wheatstone bridge.

12. The sensor according to claim 8, wherein a voltage is applied to the resistor, the voltage changing across the resistor as the resistance changes.

13. A sensor for sensing an applied load comprising:

a) substrate means;

b) resistor means mounted to the substrate means for sensing strain in response to the applied load, the resistor means generating an electrical signal that is proportional to the magnitude of the applied load;

c) conductor means mounted to the substrate means for conducting an electrical signal, the conductor means connected to opposing sides of the resistor means;

d) dielectric means mounted over the resistor means for insulating the resistor means; and

e) load transfer means mounted to the dielectric means for transferring the applied load to the resistor means.

14. The sensor according to claim 13, wherein the resistor means comprises:

a) a first strain sensitive resistor;

b) a second strain sensitive resistor;

c) a third strain sensitive resistor; and

d) a fourth strain sensitive resistor, the resistor being connected in a wheatstone bridge configuration.

15. The sensor according to claim 14, wherein the third and fourth resistors are not subjected to the applied load.

16. The sensor according to claim 13, wherein support means are mounted to the substrate means for supporting the substrate means.

17. The sensor according to claim 13, wherein a signal conditioning circuit is mounted to the substrate means and is connected to the resistor means.

18. The sensor according to claim 13, wherein the substrate means are less than 1.5 inches in length and 0.5 inches in width.