Capacitance Detection Device Using Equipotential Control Lines
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Solution Overview
Problem
In capacitive sensor devices, the two-dimensional arrangement of sensors leads to measurement errors due to the capacitance of one sensor being measured influencing the capacitance of another sensor connected to the same control line, resulting in inaccurate readings.
Innovation Solution
A capacitance detection device is designed with a sensor unit comprising multiple sensor elements arranged two-dimensionally, using row and column control lines to apply a charging voltage and connect sensors to ground potential, while an equipotential circuit sets the potential of non-measured sensors to match the measured sensor's potential, reducing cross-influence and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor elements are arranged two-dimensionally and connected to common control lines, then the device complexity is reduced and ease of operation is improved, but measurement precision deteriorates due to capacitance interference between adjacent sensors
Solution Approach 1:
The control lines are segmented into measurement-specific connections. During measurement of a specific sensor element, only the row and column control lines connected to that element are actively used, while other control lines are isolated or set to high impedance state. This segmentation prevents capacitance coupling from adjacent sensors sharing the same control lines, thereby improving measurement precision while maintaining the compact two-dimensional sensor array structure
Solution Approach 2:
The equipotential circuit actively maintains all unused control lines at the same potential as the sensor element being measured. By setting the potential of non-measured sensors equal to the measured sensor's potential, voltage differences across parasitic capacitances are eliminated, preventing capacitive coupling effects. This equipotential approach resolves the measurement accuracy issue while preserving the simplified two-dimensional sensor layout with shared control lines
2Productivity
If all sensor elements connected to the same control line are measured simultaneously, then productivity is improved, but measurement precision deteriorates due to mutual capacitance influence
Solution Approach 1:
The measurement process employs periodic sequential scanning of sensor elements rather than simultaneous measurement. The control circuit systematically selects and measures one sensor element at a time by activating specific row and column control line pairs in sequence. This periodic measurement approach eliminates mutual capacitance interference between simultaneously measured sensors, ensuring high measurement precision while maintaining acceptable productivity through efficient sequential scanning algorithms
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
This configuration effectively reduces the influence of other sensor capacitances on the measurement, enhancing the accuracy of capacitance detection by isolating the potential of non-measured sensors from the measurement process.
Implementation Method 1
a sensor unit including a plurality of sensor elements which are arranged two-dimensionally and whose capacitances change
Data Source
AI summary
A capacitance detection device includes: a sensor unit including a plurality of sensor elements; row control lines; column control lines; a control circuit supplying a charging voltage to the sensor element; and an equipotential circuit outputting a potential equal to the potential of the sensor element subject to measurement. The control circuit applies a charging voltage to the row control line connected to the sensor element and connects the column control line connected to the sensor element to the ground potential side. The control circuit causes the equipotential circuit to set a potential of at least one of the row control lines other than the row control line connected to the sensor element subject to measurement and the column control lines other than the column control line connected to the sensor element subject to measurement to a potential equal to the potential of the sensor element subject to measurement.