APPARATUS FOR DETERMINING THE COORDINATES OF AN OBJECT, MOVEABLE ALONG AT LEAST ONE COORDINATE AXIS

• US 3,843,924 A
• Filed: 02/15/1974
• Issued: 10/22/1974
• Est. Priority Date: 09/20/1972
• Status: Expired due to Term

• Current Assignee: Bjorn Wahlgren
• Original Assignee: Bjorn Wahlgren
• Inventors: Wahlgren, Bjorn
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US05/442,853
• Time in Patent Office: 249 Days
• Field of Search: 324/61R,61P 317/246 340/200 329/93
• US Class Current: 324/725
• CPC Class Codes: A61B 2503/40 Animals
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/1113 Local tracking of patients, e.g. in a hospital or private home
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24

Abstract

To determine one coordinate of an object moveable in a single plane, three electrodes are spaced from each other and connected in a circuit to measure and compare the value of capacitance between one electrode and each of the other two electrodes; the electrodes are arranged so that the two values of capacitance are assymetrically changed by movement of the object in the direction of the measured coordinate while being unchanged by movement along the other coordinate. A second set of electrodes can be used to measure that other coordinate. Six electrodes can also be arranged to allow similar measurement and comparison of four capacitive values to determine a single coordinate of an object moveable in three-coordinate space.

Claims

1. Apparatus for determining at least one coordinate of a living organism moveable over a plane surface, characterized in, that the apparatus for each coordinate determination comprises three parallel rod-shaped capacitance electrodes, two of said electrodes arranged perpendicular to the respective coordinate axis along two opposite sides of the surface and outside said surface and the third rod-shaped electrode arranged in parallel with said first electrodes, and at equal distance from said electrodes but not in the same plane as these electrodes, said electrodes to be connected in an electrical circuit from which the object to be measured is excluded for measuring differences in values of capacity between one of the three electrodes and each of the respective remaining electrodes, the difference of capacitance between each of said first electrodes and said third constituting a measure of the coordinate of the object.

2. Apparatus according to claim 1, for determining at least one coordinate of a living organism moveable within a determined space, characterized in, that for each coordinate determination the apparatus comprises at least six parallel rod-shaped electrodes, the first two of said electrodes arranged perpendicular to the coordinate axis outside said space and at two opposite sides of the space, at least four further electrodes arranged outside said space, paraLlel to said first electrodes and symmetrically with respect to each other, the four further electrodes being electrically connected together, all of said electrodes to be connected in said electrical circuit, the difference of capacitance between each of said first electrodes and said four further electrodes constituting a measure of the coordinate of the object.