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Capacitively Driven Sectioned Tablet

IP.com Disclosure Number: IPCOM000079929D
Original Publication Date: 1973-Sep-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 7 page(s) / 133K

Publishing Venue

IBM

Related People

Dym, H: AUTHOR [+2]

Abstract

In the single direction position transducing arrangement shown in Fig. 1, conductive grid lines or strips 1'-15' are shown conductively connected to the respective capacitor plates 21'-35'. Plates 21'-35' are of the same material as and integral with the conductive grid lines, so the grid lines widen at the ends into capacitive coupling pads. Position sensing in Fig. 1 is in the X-direction. Between each respective plate 21'-35' and triangular plate 17' beneath these plates there is a layer of dielectric. Thus plates 21'-35' are capacitively coupled to plate 17' to provide an array of capacitances 16'. The cutaway portions of plates 33' to 35' show dielectric at 32' and 34'.

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Capacitively Driven Sectioned Tablet

In the single direction position transducing arrangement shown in Fig. 1, conductive grid lines or strips 1'-15' are shown conductively connected to the respective capacitor plates 21'-35'. Plates 21'-35' are of the same material as and integral with the conductive grid lines, so the grid lines widen at the ends into capacitive coupling pads. Position sensing in Fig. 1 is in the X-direction. Between each respective plate 21'-35' and triangular plate 17' beneath these plates there is a layer of dielectric. Thus plates 21'-35' are capacitively coupled to plate 17' to provide an array of capacitances 16'. The cutaway portions of plates 33' to 35' show dielectric at 32' and 34'.

Also capacitively coupled to each of the grid lines 1'-15' is plate 19', acting to provide a fixed capacitance voltage division path to ground for each grid line with the grid lines, acting as voltage taps for the divided voltage. Between each of the grid lines 1'-15' and plate 19' is dielectric shown at 12' and 14', of uniform thickness across the array.

In Fig. 1, the area of the respective capacitance plates of the array of capacitances 16' increases in size in the X-direction. When plate 17' is energized by AC source 18, voltage appearing on respective grid lines 1,-15,, increases in the same direction. Voltage changes as a function of position in the X-direction because of the geometry of plate 17'. With each plate 21'-35' of equal width and equally spaced in the X-direction, the output voltage sensed on grid lines 1'-15' changes from grid line to grid line.

Fig. 2 is an exploded view of a capacitive voltage divider arrangement for sensing position in both the X and Y directions, as indicated by the arrows adjacent plates 7 and 46, respectively. Instead of the single triangular X-drive plate shown in Fig. 1 at 17', there are shown complementary pairs of triangular drive plates including complementary X-drive plates 5 and 7 in the lower part of Fig. 2, and a complementary pair of X-drive plates, 9 and 10. The second complementary pair of plates insure high reliability in position sensing, balance and symmetry. If any X-direction grid line 11-25 breaks, both segments of the broken grid line continue to provide a voltage for sensing position. Drive plates 9 and 10 are voltage driven simultaneously with plates 5 and 7. Complementary pair X-drive plates 5-7 and 9-10 act, respectively, with capacitor plates 51, 53, etc. and 71, 73, etc., to capacitively couple, in varying amounts, the transducer drive signal from AC source 18 to X-direction sensing grid lines 11-25 via an interposed dielectric medium, not shown.

There is a set of complementary pairs of Y-drive plates, 46-47 and 48-49 which function in the same manner for voltage sensing in the Y-direction.

The transducer tablet is fabricated by depositing the X-grid lines 11-25 with their corresponding capacitor plates 51,53,71,73, etc. and Y-drive plates 46-49 on one side o...