Sensor for indicating changes in the presence of persons or objects

• US 6,407,556 B1
• Filed: 11/03/1999
• Issued: 06/18/2002
• Est. Priority Date: 03/06/1997
• Status: Expired due to Fees

• Current Assignee: Jan Rudeke
• Original Assignee: Jan Rudeke
• Inventors: Rudeke, Jan
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): HAMDAN, WASSEEM H
• Application Number:
  US09/380,544
• Time in Patent Office: 958 Days
• Field of Search: 324/663, 324/671, 324/672, 324/674, 324/686, 324/687, 340/562
• US Class Current: 324/663
• CPC Class Codes: G08B 13/26 by proximity of an intruder causing variation in capacitance or inductance of a circuit

Abstract

A sensor for indicating changes in the physical presence of persons or objects and including at least two electrically conductive sheets of material that are spaced mutually apart on an electrically non-conductive carrier sheet or the like. A sensing circuit is also provided for sensing changes in the capacitance between the electrically conductive sheets.

Claims

1. A sensor for indicating changes in the physical presence of persons or objects comprising:

at least one sensor field including at least two sheets of electrically conductive material spaced mutually apart on a flexible electrically non-conductive plastic carrier sheet, and,

a sensing circuit which detects changes in capacitance between the two sheets of electrically conductive material so as to provide an indication of said changes in physical presence, and

wherein the electrically conductive sheets are comprised of a polymeric material that includes a pulverized electrically conductive material including carbon.

2. A sensor according to claim 1, wherein the sheets are juxtapositioned on said carrier sheet.

3. A sensor according to claim 1, wherein said at least one sensor field comprises two or more different fields of at least two sheets of electrically conductive material, said capacitance being measured between mutually adjacent sheets of electrically conductive material within each field.

4. A sensor according to claim 1 wherein the sensing circuit is designed to generate an electric signal when the capacitance changes by a predetermined value within a predetermined time period.

5. A sensor for indicating changes in the physical presence of persons or objects comprising:

at least one sensor field including at least two sheets of electrically conductive material spaced mutually apart on flexible electrically non-conductive carrier means, and,

a sensor circuit which detects changes in capacitance between the sheets of electrically conductive material so as to provide an indication of said changes in physical presence, and

wherein the electrically conductive sheets are comprised of a polymeric material that includes a pulverized electrically conductive material.

6. A sensor for indicating changes in the physical presence of persons or objects comprising:

at least one sensor field including at least two coplanar sheets of electrically conductive material spaced mutually apart on electrically non-conductive carrier means, and,

a sensing circuit which detects changes in capacitance between the sheets of electrically conductive material so as to provide an indication of said changes in physical presence, and

wherein the electrically conductive sheets are comprised of a polymeric material that includes a pulverized electrically conductive material.

7. A sensor according to claim 6 wherein said non-conductive carrier means comprises a flexible non-conductive carrier sheet.

8. A sensor according to claim 7 wherein said carrier sheet is comprised of plastic.

9. A sensor according to claim 6 and additionally including covering means over said at least two coplanar conductive sheets and the non-conductive carrier means.

10. A sensor according to claim 9, wherein said covering means is comprised of plastic material.

11. A sensor according to claim 7 wherein said at least one sensor field comprises plural sensor fields and said at least two sheets of conductive material comprise plural pairs of coplanar sheets of conductive material.

12. A sensor according to claim 6 wherein said at least two sheets of conductive material comprise multiple pairs of mutually aligned sheets of conductive material.

13. A sensor according to claim 12 wherein said sheets are arranged in rows and columns.

14. A sensor according to claim 6 wherein the pulverized electrically conductive material includes carbon.