Device for two-dimensional localization of events that generate current on a resistive surface

• US 4,788,384 A
• Filed: 12/17/1987
• Issued: 11/29/1988
• Est. Priority Date: 12/18/1986
• Status: Expired due to Fees

• Current Assignee: Etbalissement Public Centre National de La Recherche Scientifique
• Original Assignee: Centre National De La Recherche Scientifique
• Inventors: Marechal, Bernard M., DeSouza, Marcio N., Bruere-Dawson, Roger, Froissart, Marcel
• Primary Examiner(s): SCHREYER, STAFFORD
• Application Number:
  US07/134,354
• Time in Patent Office: 348 Days
• Field of Search: 178/18, 178/19
• US Class Current: 178/18.05
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

Electrodes are placed at the periphery of a resistive surface to pick up a current generated at a point on the resistive surface. Each electrode is connected to at least three summing lines via respective resistors each having a fixed resistance value which is predetermined as a function of the summing line and of the electrode in such a manner as to obtain analog signals from at least two of the summing lines which are linear functions of respective co-ordinates (with respect to a predetermined co-ordinate system) of a point on the resistive surface at which current is generated.

Claims

1. A device for two-dimensional localization of current-generating events on a resistive surface, the device comprising:

a resistive surface;

a plurality of electrodes fixed to the resistive surface around its periphery in order to pick up currents generated by injecting current or electric charge into points on the resistive surface; and

at least three current summing lines connected to the electrodes via discrete resistive components in such a manner as to obtain analog signals on said summing lines whose amplitudes are functions of the co-ordinates of said points in a predetermined reference co-ordinate system;

the device including the improvement whereby;

each of said electrodes is connected by means of respective resistive components to at least three summing lines in such a manner that at least two of the said lines deliver analog signals whose amplitudes are substantially linear functions of the desired co-ordinates.

2. A device according to claim 1, wherein the number of electrodes is selected in such a manner that the distance between successive pairs of adjacent electrodes is no greater than the acceptable width of a peripheral distortion margin on the resistive surface.

3. A device according to claim 2, having at least 16 electrodes.

4. A device according to claim 1, wherein the signal obtained on one of said summing lines varies as a linear function of one co-ordinate and the signal obtained on another of said summing lines varies as a linear function of the other co-ordinate.

5. A device according to claim 4, having four summing lines, wherein the signals obtained on the summing lines are the same linear functions respectively of:

a first co-ordinate, minus said first co-ordinate, the other co-ordinate, and minus said other co-ordinate.

6. A device according to claim 5, including means for generating two analog signals whose amplitudes are proportional to the co-ordinates by performing a linear combination of the signals obtained on the summing lines.

7. A device according to claim 1, wherein the sum of the conductances connecting any of the electrodes to the summing lines has a predetermined fixed value G such that R.sub.□

is greater than or of the same order as;

(1/G);

where R.sub.□

is the surface resistivity of the resistive surface and N is the number of electrodes.

8. A device according to claim 7, wherein the signals obtained on the summing lines are amplified by means of amplifiers having respective input impedances Z such that Z is less than or of the same order as:

##EQU1##

9. A device according to claim 1, wherein the resistive surface is disk-shaped.

10. A device according to claim 9, wherein the conductance G(n, 1) of the resistive connection between an electrode having θ

_n as its polar co-ordinate angle in said system of reference co-ordinates, and a summing line intended to provide a signal which is a linear function of the co-ordinate of a point localizing an event relative to an axis whose polar co-ordinate is θ

₁ in said system of reference co-ordinates, has a value which is selected to be substantially equal to K(1+cos(θ

_n -θ

₁)), where K is a predetermined constant.

11. A device according to claim 1, wherein the resistive surface is rectangular in shape.