Capacitative Node Measurement in Matrix Pressure Inducer
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Solution Overview
Problem
Existing pressure measurement technologies face errors in isolating individual node capacitance due to non-zero input impedance and dynamic variable errors from changing pressures in other nodes, complicating accurate pressure distribution mapping.
Innovation Solution
Introducing a fixed reference capacitance on each row to serve as a base measurement value, allowing for the comparison and estimation of individual node capacitance by determining the ratio of current sensor cell measurements to the fixed reference capacitance, thereby isolating the node of interest from surrounding capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grounding of unmeasured columns and rows is used to isolate the node of interest, then measurement isolation is improved, but measurement precision deteriorates due to non-zero input impedance and dynamic variable errors from changing pressures in other nodes
Solution Approach 1:
A fixed reference capacitance is introduced as an intermediary element connected to each row. This reference capacitance serves as a mediator that allows comparison between the variable node capacitance and a stable baseline, enabling the system to distinguish between changes due to the measured node versus changes due to other nodes or environmental factors. The reference capacitance acts as a control that compensates for the non-zero input impedance effects and dynamic variable errors.
Solution Approach 2:
The system changes the parameter being measured from absolute capacitance values to ratio values (node capacitance divided by reference capacitance). By transforming the measurement from C_node to C_node/C_reference, the system eliminates the effects of non-zero input impedance and dynamic variables that affect both measurements equally. This parameter transformation converts an inaccurate absolute measurement into a precise relative measurement.
2Device complexity
If conventional capacitive measurement with grounding is used, then device complexity is reduced, but measurement precision deteriorates due to error from non-zero input impedance
Solution Approach 1:
The fixed reference capacitance serves as a simple intermediary that adds minimal complexity to the system. Rather than using complex high-precision amplifiers or zero-impedance arrangements, the patent introduces a simple capacitive reference element that can be measured using the same existing circuitry, thereby improving precision without significantly increasing device complexity.
Solution Approach 2:
The reference capacitance creates a copy or duplicate measurement channel that mirrors the measurement process for the actual node. By measuring both the node capacitance and the reference capacitance through the same circuit path and then taking their ratio, the system cancels out common errors and impedance effects, achieving high precision with simple duplicated measurement paths.
3Device complexity
If multiplexing is used to scan nodes sequentially, then device complexity is reduced, but measurement precision deteriorates due to interference from surrounding nodes
Solution Approach 1:
The fixed reference capacitance on each row acts as an intermediary that remains constant during the multiplexing process. When scanning through different columns or nodes on a row, the reference capacitance provides a stable baseline that allows accurate comparison of each node's capacitance despite the sequential nature of the measurement and the presence of other nodes at different states.
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 method effectively reduces measurement errors by normalizing capacitance values, enabling accurate pressure distribution mapping across the selected area by comparing each node's capacitance to the fixed reference, thus improving the precision of pressure measurement.
Implementation Method 1
an array of sensor cells each formed at the intersection of a column and a row, and wherein each sensor cell has a capacitance that varies in accordance with compression of the insulating material at said intersection
Implementation Method 2
compression of the insulating material at said intersection
Data Source
AI summary
A method and system for measuring the distribution of pressure forces over a selected area includes a sensor having an array of pressure sensing capacitance nodes formed by intersecting rows and columns, where measured capacitance of a node is compared to a fixed value of reference capacitance placed on each row that can be measured as if it was another node.