Capacitive Position Sensor With Low-Dielectric Shielding
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Solution Overview
Problem
Conventional position detection devices face challenges in ensuring detection precision when the range of movement for a movable element is increased, due to signal leakage between electrodes, which worsens with larger movement ranges and increased electrode numbers.
Innovation Solution
A position detection device with a substrate featuring a low-dielectric constant area between electrodes and electrical signal shielding, along with a supply and detection circuit that uses multiple phase signals and capacitive coupling to accurately detect the position of a movable element, even with increased movement ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the range of possible movement of the movable element is increased, then the detection range is improved, but detection precision deteriorates due to signal leakage between electrodes
Solution Approach 1:
A low-dielectric constant area is introduced as an intermediary region between the first electrodes (signal supply) and the second electrode (signal extraction). This intermediary area with reduced dielectric constant suppresses signal leakage by reducing capacitive coupling between adjacent electrodes, thereby maintaining detection precision while allowing for increased detection range
Solution Approach 2:
The substrate is designed with non-uniform dielectric properties: the low-dielectric constant area has a specifically reduced dielectric constant compared to other portions of the substrate. This local variation in material property is strategically positioned to suppress signal leakage only in the critical region between signal supply and extraction electrodes, without affecting the overall detection range
2Measurement precision
If the interval between electrodes for signal supply is narrowed to maintain detection precision, then detection precision is improved, but the number of electrodes must increase which causes signal leakage to increase
Solution Approach 1:
The low-dielectric constant area serves as a mediator that suppresses signal leakage between electrodes even when the interval between them is narrow. By reducing the dielectric constant in this specific region, the capacitive coupling between adjacent first electrodes and the second electrode is reduced, allowing for narrower electrode spacing without increasing overall signal leakage
Solution Approach 2:
The dielectric constant parameter of the substrate is changed locally in the region between the first electrodes and the second electrode. By reducing the dielectric constant in this specific area, the electrical field distribution is modified to reduce signal leakage, enabling narrower electrode intervals to be used while maintaining detection precision and controlling signal leakage
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
The solution enables precise detection of relative positions between a fixed and movable element, reducing signal leakage and noise, thus maintaining detection accuracy even with larger movement ranges without increasing electrode numbers.
Implementation Method 1
signal leakage occurs between electrodes for supplying signals of a plurality of phases and electrodes for extracting signals
Implementation Method 2
The low-dielectric constant area has a lower dielectric constant than other portions of the substrate
Implementation Method 3
supplying a voltage to an induction electrode of a fixed element to generate an alternating potential distribution in a comb-shaped electrode of a movable element by means of capacitive coupling
Implementation Method 4
detecting the alternating potential distribution using a voltage detection electrode of the fixed element to generate a vector having two signals as its components, and measuring the relative potential of the movable element referenced to the fixed element from the rotation angle of the vector
Data Source
AI summary
A fixed element is provided to be used in a position detection device for detecting a position of a movable element that moves on the fixed element. The fixed element includes a substrate, a plurality of first electrodes and a second electrode. The substrate has as first surface, a second surface and a low-dielectric constant area. The second surface faces in an opposite direction to the first surface. The low-dielectric constant area has a lower-dielectric constant than other portions of the substrate. The first electrodes are disposed on the first surface of the substrate. The first electrodes include three or more phases arranged one-dimensionally in a repeating pattern in a movement direction of the movable element. The second electrode is disposed on the first surface of the substrate and is arranged in the movement direction of the movable element adjacent the first electrodes. The low-dielectric constant area of the substrate is provided in a position between the first electrodes and the second electrode.