Displacement sensor with mechanical preamplification means

• US 5,115,680 A
• Filed: 03/04/1991
• Issued: 05/26/1992
• Est. Priority Date: 03/04/1991
• Status: Expired due to Fees

• Current Assignee: Hyok S. Lew
• Original Assignee: Hyok S. Lew
• Inventors: Lew, Hyok S.
• Primary Examiner(s): MYRACLE, JERRY
• Application Number:
  US07/663,733
• Time in Patent Office: 449 Days
• Field of Search: 73/763, 73/774, 73/782, 73/866.1, 33/787, 33/788, 33/789
• US Class Current: 73/763
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01B 7/22 using change in capacitance
• CPC Class Codes: G01F 1/206 Measuring pressure, force or momentum of a fluid flow which is forced to change its direction
• CPC Class Codes: G01F 1/80 operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
• CPC Class Codes: G01G 3/12 wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
• CPC Class Codes: G01G 3/1402 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 1/142 using capacitors
• 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
• CPC Class Codes: G01L 9/0002 using variations in ohmic resistance G01L9/0051 takes precedence
• CPC Class Codes: G01L 9/0005 using variations in capacitance G01L9/0072 takes precedence
• CPC Class Codes: G01L 9/0038 using variations in capacitance

Abstract

A device for measuring physical variables comprises a pair of thin planar members disposed symmetrically in a face-to-face arrangement about a plane including a reference axis defining the direction of displacement of a target object mechanically coupled to the pair of thin planar members, wherein the displacement in a first direction parallel to the reference axis increases the separation distance between the pair of thin planar members and the displacement in a second direction opposite to the first direction decreases the separation distance between the pair of thin planar members. The physical variable related to the displacement is determined as a function of an electrical parameter varying as a function of the separation distance between the pair of thin planar members such as the electrical capacitance or resistance therebetween measured by a capacitance or ohm meter.

Claims

1. A device for measuring physical variable related to displacement of a target object comprising in combination:

a) at least one thin planar member with two opposite extremities respectively supported by two supporting members disposed in an arrangement wherein at least one of the two support members is movable relative to the other of the two support members on a plane including the two opposite extremities of the thin planar member, said thin planar member constituting a first electrical terminal;

b) means for transmitting displacement of the target object to said at least one of the two support members, wherein increase of relative distance between the two support members decreases bending deflection of the thin planar member and decrease of the relative distance between the two support members increases bending deflection of the thin planar member;

c) a second electrical terminal disposed next to the thin planar member constituting the first electrical terminal in an arrangement wherein electrical resistance between the first and second electrical terminals varies as a function of bending deflection of the thin planar member; and

d) means for measuring electrical resistance between the first and second electrical terminals as a measure of displacement of the target object.

2. A combination as set forth in claim 1 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical resistance between the first and second electrical terminals.

3. A combination as set forth in claim 1 wherein another thin planar member disposed next to said at least one thin planar member in a face-to-face arrangement and supported by the two support members respectively at two opposite extremities thereof constitutes the second electrical terminal, wherein said at least one and another thin planar members bend in a mirror image to one another about a plane therebetween as relative distance between the two support members changes.

4. A combination as set forth in claim 3 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical resistance between the first and second electrical terminals.

5. A combination as set forth in claim 1 wherein at least one elongated member disposed next to said at least one thin planar member constitutes the second electrical terminal, wherein the contact surface area between the elongated member and the thin planar member increases with increasing bending deflection of the thin planar member and vice versa, and the electrical resistance between the elongated member and the thin planar member changes as the contact surface area therebetween changes.

6. A combination as set forth in claim 5 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical resistance between the first and second electrical terminals.

7. A combination as set forth in claim 1 wherein said combination includes a third electrical terminal disposed next to the thin planar member in an arrangement wherein the second and third electrical terminals are disposed on the two opposite sides of the thin planar member, and further includes means for measuring electrical resistance between the first and third electrical terminals as another measure of displacement of the target object.

8. A combination as set forth in claim 7 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical resistance between the first and second electrical terminals and electrical resistance between the first and third electrical terminals.

9. A combination as set forth in claim 1 wherein said combination includes another device for measuring physical variables comprising the same elements included in said a device for measuring physical variables, wherein the displacement of the target member in a first direction increases bending deflection of the thin planar member included in said a device and decreases bending deflection of the thin planar member included in said another device, and the displacement of the target member in a second direction opposite to said first direction decreases bending deflection of the thin planar member included in said a device and increases bending deflection of the thin planar member included in said another device.

10. A combination as set forth in claim 9 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical resistance between the first and second electrical terminals included in said a device and electrical resistance between the first and second electrical terminals included in said another device.

11. A combination as set forth in claim 9 wherein the second electrical terminal included in each of said a and another devices comprises another thin planar member disposed next to said at least one thin planar member in a face-to-face arrangement and supported by the two support members respectively at the two opposite extremities thereof, wherein said at least one and another thin planar members bend in a mirror image to one another about a plane therebetween as the displacement of the target object changes.

12. A combination as set forth in claim 9 wherein the second electrical terminal included in each of said a and another devices comprises at least one elongated member disposed next to said at least one thin planar member, wherein the contact surface area between the elongated member and the thin planar member increases with increasing bending deflection of the thin planar member and vice versa, and electrical resistance between the elongated member and the thin planar member changes as the contact surface area therebetween changes.

13. A device for measuring physical variable related to displacement of a target object comprising in combination:

a) at least one thin planar member with two opposite extremities respectively supported by two supporting members disposed in an arrangement wherein at least one of the two support members is movable relative to the other of the two support members on a plane including the two opposite extremities of the thin planar member, said thin planar member constituting a first electrical terminal;

b) means for transmitting displacement of the target object to said at least one of the two support members, wherein increase of relative distance between the two support members decreases bending deflection of the thin planar member and decrease of relative distance between the two support members increases bending deflection of the thin planar member;

c) a second electrical terminal disposed in a stationary arrangement on one side of the thin planar member and a third electrical terminal disposed in a stationary arrangement on the other side of the thin planar member opposite to said one side; and

d) a first means for measuring electrical capacitance between the first and second electrical terminals and a second means for measuring electrical capacitance between the first and third electrical terminals as measures of displacement of the target object.

14. A combination as set forth in claim 13 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical capacitance between the first and second electrical terminals and electrical capacitance between the first and third electrical terminals.

15. A combination as set forth in claim 13 wherein each of the second and third electrical terminals comprises a rigid planar member disposed in a fixed arrangement parallel to said at least one thin planar member.

16. A combination as set forth in claim 15 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical capacitance between the first and second electrical terminals and electrical capacitance between the first and third electrical terminals.

17. A combination as set forth in claim 15 wherein said combination includes another thin planar member made of a dielectric material disposed next to said at least one thin planar member in a face-to-face arrangement and supported by the two support members respectively at two opposite extremities thereof, wherein said at least one and another thin planar members bend in a mirror image to one another about a plane therebetween as relative distance between the two support members changes.

18. A combination as set forth in claim 17 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical capacitance between the first and second electrical terminals and electrical capacitance between the first and third electrical terminals.

19. A combination as set forth in claim 13 wherein said combination includes another thin planar member made of a dielectric material disposed next to said at least one thin planar member in a face-to-face arrangement and supported by the two support members respectively at two opposite extremities thereof, wherein said at least one and another thin planar members bend in a mirror image to one another about a plane therebetween as relative distance between the two support members changes.

20. A combination as set forth in claim 19 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical capacitance between the first and second electrical terminals and electrical capacitance between the first and third electrical terminals.

21. A device for measuring physical variable related to displacement of a target comprising in combination:

a) a first pair of thin planar members disposed in a side-by-side arrangement and supported by two support members respectively at opposite extremities thereof, wherein at least one of the two support members is movable relative to the other of the two support members on a plane intermediate the first pair of thin planar members, and the first pair of thin planar members bend in a mirror image to one another about the plane therebetween as relative distance between the two support members changes;

b) a second pair of thin planar members disposed in a side-by-side arrangement and supported by two support members respectively at opposite extremities thereof, wherein at least one of the two support members is movable relative to the other of the two support members on a plane intermediate the second pair of thin planar members, and the second pair of thin planar members bend in a mirror image to one another about the plane therebetween as relative distance between the two support members changes;

c) means for transmitting displacement of the target object to said at least one of the two support members supporting the first pair of thin planar members and to said at least one of the two support members supporting the second pair of thin planar members, wherein displacement of the target object in a first direction increases bending deflection of the first pair of thin planar members and decreases bending deflection of the second pair of thin planar members, and displacement of the target object in a second direction opposite to said one direction decreases bending deflection of the first pair of thin planar members and increases bending deflection of the second pair of thin planar members; and

d) a first means for measuring electrical capacitance between the first pair of thin planar members, and a second means for measuring electrical capacitance between the second pair of thin planar members as measures of displacement of the target object.

22. A combination as set forth in claim 21 wherein said combination includes means for determining numerical value of the physical variable as a function of electrical capacitance between the first pair of thin planar members and electrical capacitance between the second pair of thin planar members.