Output circuit for piezoelectric polymer pressure sensor

• US 4,328,441 A
• Filed: 01/31/1980
• Issued: 05/04/1982
• Est. Priority Date: 01/31/1980
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Kroeger, Frederick R. Jr., Norquist, Richard A.
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US06/117,296
• Time in Patent Office: 824 Days
• Field of Search: 310/339, 310/317, 310/319, 310/800, 340/365 A
• US Class Current: 310/319
• CPC Class Codes: G01L 1/162 using piezoelectric resonators
• CPC Class Codes: H03K 17/964 Piezoelectric touch switches
• CPC Class Codes: H10N 30/302 Sensors
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

A pressure sensitive apparatus for producing electrical signals on two electrodes having a layered structure consisting of a conductive layer, a piezoelectric polymer film layer, an electrode layer, an insulating layer, another electrode layer, another piezoelectric polymer film layer, and another conductive layer. The layered structure may be constructed from an insulating layer sandwiched between two piezoelectric polymer films each having an electrode on one surface thereof and having a conductive plane on the other surface thereof disposed on each side of the insulating layer with the electrodes in closest proximity to the insulating film. Further, support substrates may be disposed on each side of the piezoelectric polymer films, the support substrates having an opening where the electrodes are located. Still, further, the apparatus may be adapted for a pressure sensitive matrix keyboard having a plurality of keyboard switch positions arranged in a plurality of rows and columns where the electrodes are a strip constituting one of the rows and columns, respectively, of the keyboard switch positions. The piezoelectric polymer film may be polyvinylidene fluoride and the layered structure may be integrally bonded or physically sandwiched together and may have connected to it an electrical sensing circuit suitable for amplifying a small charge pulse induced by the strain upon the piezoelectric polymer film.

Claims

1. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a high impedance interface to said one of said two electrodes which provides for an adjustable sensitivity;

said electrical sensing circuit having an MOS digital gate adapted to be powered from a power source having a voltage and a signal ground and having a signal input and a signal output, said signal input coupled to said one of said two electrodes;

a first resistance coupled between said voltage and said signal ground and having an adjustable tap to bias said digital gate; and

a second resistance coupled between said signal input and said adjustable tap to provide an adjustment of the bias of said digital gate.

2. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, and conductive plane being utilized as signal ground;

said electrical sensing circuit being a high impedance interface to said one of said two electrodes which provides for an adjustable sensitivity;

said one of said two electrodes being positively charged with respect to said conductive plane and said electrical circuit having a comparator adapted to be powered from a power source having a voltage and a signal ground and having first and second signal inputs and a signal output, said first signal input being coupled to said one of said two electrodes, a first resistance coupled between said voltage and said second signal input, a second resistance coupled between said second signal input and said signal ground and having an adjustable tape and a third resistance coupled between said first signal input and said adjustable tap such that said first, second and third resistance provide an adjustable bias for said comparator.

3. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a high impedance interface to said one of said two electrodes which provides for an adjustable sensitivity;

said one of said two electrodes being negatively charged with respect to said conductive plane and said electrical circuit having a comparator adapted to be powered from a power source having a voltage and a signal ground and having first and second signal inputs and a signal output, said first signal input coupled to said one of said two electrodes;

a first resistance coupled between said second signal input and signal ground, a second resistance coupled between said second signal input and said voltage and having an adjustable tap and a third resistance coupled between said first signal input and said adjustable tap such that said first, second and third resistance provide an adjustable bias for said comparator.

4. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a high impedance interface to said one of said two electrodes which provides for an adjustable sensitivity;

said one of said two electrodes being positively charged with respect to said conductive plane and said electrical circuit having a comparator adapted to be powered from a power source having a positive voltage and a negative voltage and having first and second signal inputs and a signal output, said first signal input coupled to said one of said two electrodes and said second signal input coupled to signal ground, a first resistance coupled between said second signal input and said negative voltage and having an adjustable tap and a second resistance coupled between first signal input and said adjustable tap such that said first and second resistances provide an adjustable bias for said comparator.

5. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a high impedance interface to said one of said two electrodes which provides for an adjustable sensitivity;

said one of said two electrodes being negatively charged with respect to said conductive plane and said electrical circuit having a comparator adapted to be powered from a power source having a positive voltage and a negative voltage and having first and second signal inputs and a signal output, said first signal input coupled to said one of said two electrodes and said second signal input coupled to signal input coupled to signal ground, a first resistance coupled between said second signal input and said positive voltage and having an adjustable tap and a second resistance coupled between first signal input and said adjustable tap such that said first resistance and said second resistance provide an adjustable bias for said comparator.

6. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a low impedance interface to said one of said two electrodes;

said one of said two electrodes being positively charged with respect to said conductive plane and said electrical circuit having an operational amplifier adapted to be powered from a power source having a positive voltage and a negative voltage, said operational amplifier having an inverting input and a non-inverting input and a signal output, said inverting input being coupled to said one of said two electrodes and said non-inverting input being coupled to signal ground, a first resistance being coupled between said signal output and said inverting input, and a second resistance being coupled between said inverting input and said negative voltage.

7. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a low impedance interface to said one of said two electrodes

said one of said two electrodes being negatively charged with respect to said conductive plane and wherein said electrical circuit having an operational amplifier adapted to be powered from a power source having a positive voltage and a negative voltage, said operational amplifier having an inverting input and a non-inverting input and a signal output, said inverting input being coupled to said one of said two electrodes and said non-inverting input being coupled to signal ground, a first resistance being coupled between said signal output and said inverting input, and a second resistance being coupled between said inverting input and said positive voltage.

8. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a low impedance interface to said one of said two electrodes;

said one of said two electrodes being positively charged with respect to said conductive plane and said electrical circuit having a "Norton" amplifier adapted to be powered from a power source having a positive voltage and a signal ground, said "Norton" amplifier having an inverting input and a non-inverting input and a signal output, said inverting input being coupled to said one of said two electrodes, and a resistance coupled between said non-inverting input and said positive voltage.

9. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a low impedance interface to said one of said two electrodes;

said one of said two electrodes being negatively charged with respect to said conductive plane and said electrical circuit having a "Norton" amplifier adapted to be powered from a power source having a positive voltage and a signal ground, said "Norton" amplifier having an inverting input and a non-inverting input and a signal output, said inverting input being coupled to said one of said two electrodes, a first resistance coupled between said non-inverting input and said positive voltage, and a second resistance coupled between said inverting input and said positive voltage, where said first resistance is greater than said second resistance.

10. A pressure sensitive apparatus for producing an amplified electrical signal on one of two electrodes comprising:

an insulating layer;

two piezoelectric polymer films, each having one of said two electrodes on one surface thereof and having a conductive plane on the other surface thereof adapted to be connected to ground, one disposed on each side of said insulating layer with said electrodes in closest proximity to said insulating film; and

an electrical sensing circuit coupled to said one of said two electrodes and coupled to said conductive plane for amplifying one of said electrical signals, said conductive plane being utilized as signal ground;

said electrical sensing circuit being a low impedance interface to said one of said two electrodes,

said one of said two electrodes being negatively charged with respect to said conductive plane and said electrical circuit having a "Norton" amplifier adapted to be powered from a power source having a positive voltage and a signal ground, said "Norton" amplifier having an inverting input and a non-inverting input and a signal output, said non-inverting input being coupled to said one of said two electrodes, and a first resistance coupled between said inverting input and said positive voltage, and a second resistance coupled between said non-inverting input and said positive voltage, where said first resistance is greater than said second resistance.