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Main >> Applications >> Sample problems

Touchscreen - QuickField simulation example

Currents at the four corner electrodes of a capacitive touchscreen versus touch position, showing the electrical signals used to determine contact location.
Electric potential is applied to the electrodes in the four corners of the conductive sheet. Conductive object with zero potential boundary touches the sheet and the currents in the electrodes depend on the touch position.

Engineering question

How to calculate the four corner-electrode currents as a function of touch position in this touchscreen model?

Answer
Simulate each grounded touch position in a plane-parallel DC-conduction model and calculate the currents at electrodes A, B, C, and D.

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Typical applications
capacitive touchscreens, grounded touch panels, finger sensing surfaces

Touchscreen

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Simulation problem

Problem Type
Plane-parallel problem of DC Conduction.

Geometry
Touchscreen Currents at the four corner electrodes of a capacitive touchscreen versus touch position, showing the electrical signals used to determine contact location. Finger A B C D 100 mm 200 mm
Screen thickness is 0.1 mm

Given
Electrical conductivity of the touchscreen 100 S/m.
A,B,C,D electrodes voltage +1V.
Finger voltage 0V.

Task
Determine the currents in A,B,C,D electrodes as a function of the touchosition.

Solution
Different touch positions are simulated by separate models. Creation of the new problems, geometry model modification and results measurements are automated with LabelMover.

Results
Electric field distribution in touch screen.
Touchscreen

Due to symmetry you can use a single chart to measure all electrodes currents. Origin x=0, y=0 correspons to the center of the touch screen.

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