Touch sensor matrix - QuickField simulation example
Touch sensor matrix can detect the human finger position. It is an essential part of the capacitive touch screen. The matrix consists of two groups of electrodes: transmitters and receivers.
How to calculate the capacitance change caused by a finger on a touch sensor matrix?
Answer Typical applications Geometry
Given
Task
Solution
Results
Engineering question
Model the touch sensor in 3D electrostatics with the finger as a floating conductor and compare electrode capacitances with and without the finger.
capacitive touchscreen matrices, electrode grid sensors, touch panel electrodes
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Simulation problem
Problem Type
3D problem of electrostatics.
Relative permittivity of the materials: board 4.3, film 2, glass 5.
Determine the mutual capacitances between Tx and Rx electrodes for an arbitrary finger position.
Finger is simulated as a floating conductor.
If we energize one pair of Tx and Rx electrodes with +1V and -1V electric potentials and leave other electrodes floating, then the mutual capacitance between these electrodes can be calclated as
C = 2 * Energy / ( Potential difference )²
Two problems are simulated: open air and with a finger. The variation of the capacitance is calculated then.
Electric field distribution around the touch sensor. Capacitances open air is 1.5 pF, capacitance with finger is 1.63 pF.
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