Touch sensor capacitance - QuickField simulation example
Touch sensor consists of two circular electrodes, transmitting Tx and receiving Rx rings, placed on the dielectric board. Presence of the conductive stylus in their vicinity affects the capacitance between electrodes.
How to calculate the effect of stylus distance on the capacitance between a touch sensor's Tx and Rx electrodes?
Answer Typical applications Geometry
Conducting rings thickness is 35 μm.
Given
Task
Solution
Results
Engineering question
Treat the stylus as a floating conductor and use LabelMover to sweep its distance while calculating capacitance from charge over Tx–Rx potential difference.
capacitive stylus sensors, touch electrodes, proximity sensing elements
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Simulation problem
Problem Type
Axisymmetric problem of electrostatics.
Relative permittivity of dielectric is 4.7.
Determine the capacitance of Tx and Rx electrodes as a function of a distance between the touch sensor and the stylus.
"Floating conductor" boundary condition is assigned to the stylus surface, there is no field inside the conductor.
Capacitance is a ratio of stored charge q to the potential difference ΔU between Rx and Tx electrodes.
Simulations are performed for different stylus positions. LabelMover tool is used to automate the series of calculations.
Electric field distribution in and around the touch sensor:
Video
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