Capacitive Sensor Proximity Pressing Distinction
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Solution Overview
Problem
Conventional capacitive sensors fail to accurately distinguish between the proximity of a finger and pressing force due to the simultaneous influence on both first and second capacitance measurements.
Innovation Solution
A capacitive sensor design featuring front-side electrodes, an elastic dielectric body, a shield electrode, and a variable alternating-current voltage output unit that differentiates between capacitance changes caused by proximity and pressing by adjusting the amplitude of the alternating-current voltage applied to the shield electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both first capacitance and second capacitance are measured simultaneously, then the sensor can detect both proximity and pressing events, but it becomes impossible to accurately distinguish pressing events from proximity events
Solution Approach 1:
The patent segments the capacitance measurement into two distinct phases: first capacitance measurement (when switch S2 is closed) and second capacitance measurement (when switch S2 is open). This temporal segmentation allows the sensor to separately measure and analyze capacitance changes caused by proximity versus pressing events, resolving the ambiguity that occurs when both measurements are performed simultaneously.
Solution Approach 2:
The patent introduces dynamic switching control of switch S2 to change the measurement configuration over time. By dynamically opening and closing switch S2, the system transitions between different measurement modes (first capacitance measurement mode and second capacitance measurement mode), enabling the sensor to adaptively distinguish between proximity and pressing events based on the temporal pattern of capacitance changes.
2Measurement precision
If the sensor structure includes both detection electrodes and shield electrodes with elastic dielectric bodies, then the sensor can differentiate between proximity and pressing, but the device complexity increases
Solution Approach 1:
The detection electrodes serve multiple functions: they participate in both the first capacitance measurement (for proximity detection) and the second capacitance measurement (for pressing detection). The shield electrodes similarly serve dual purposes by being involved in both measurement phases. This multi-functionality reduces the need for separate dedicated components for each detection type, thereby limiting the increase in device complexity while achieving event differentiation.
Solution Approach 2:
The patent adds the temporal dimension to the capacitance measurement process by introducing time-based switching control. Instead of using only spatial separation (which would require more physical components), the system uses the time dimension to separate different measurement functions, allowing the same physical components to serve multiple purposes and reducing overall structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate detection of pressing events by isolating capacitance changes associated with pressing from those caused by proximity, thereby improving the sensor's ability to discern and respond to pressing actions.
Implementation Method 1
an elastic dielectric body disposed on the back side of the one or plurality of front-side electrodes
Implementation Method 2
a second voltage output unit that outputs, to the shield electrode, a second alternating-current voltage... a detection unit connected to the one or more detection electrodes, the detection unit detecting an output matching capacitances
Data Source
AI summary
A capacitive sensor includes: front-side electrodes including a detection electrode; a cover that covers the front-side electrodes; an elastic dielectric body below the front-side electrodes; a shield electrode below the elastic dielectric body; a first voltage output unit that outputs a first alternating-current voltage to a driving unit coupled to the detection electrode; a second voltage output unit that outputs, to the shield electrode, a second alternating-current voltage having the same phase as the first alternating-current voltage; a detection unit connected to the detection electrode, the detection unit detecting an output matching capacitances among the front-side electrodes; and an operation decision unit that decides whether the cover has been pressed with a detection target, according to a plurality of outputs from the detection unit, the plurality of outputs being obtained when the second voltage output unit changes the amplitude of the second alternating-current voltage to a plurality of amplitudes.