Trapezoidal Transmitting Electrode for Linear Capacitive Grating Sensing
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Solution Overview
Problem
Conventional capacitive grating displacement sensors suffer from non-linear measurement errors due to the finite width of insulating grooves between transmitting electrodes, which limits measurement accuracy and introduces substantial non-linearity, and reducing these gaps is difficult and costly.
Innovation Solution
The transmitting electrode is configured as a series of mutually inverted trapezoidal structures on the movable grating plate, with specific dimensions and alignments to minimize abrupt non-linear errors, ensuring linear capacitance variation and improved manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional rectangular transmitting electrodes with insulating grooves are used, then manufacturing is simplified using standard PCB processes, but measurement accuracy deteriorates due to non-linear errors from groove alignment
Solution Approach 1:
The transmitting electrode is segmented into multiple trapezoidal structures arranged in sequence along the sliding direction. Each trapezoidal structure has a varying width that tapers from the large base to the small base, creating a continuous capacitance variation pattern that eliminates abrupt non-linear errors when gaps align with stationary electrode edges.
Solution Approach 2:
The electrode geometry transitions from simple rectangular shapes to trapezoidal shapes with varying widths. This dimensional change in the electrode profile creates a gradual capacitance transition that compensates for the discrete gap structure, maintaining measurement linearity while preserving PCB manufacturability.
2Measurement precision
If the inter-electrode gap is reduced to less than 0.076 mm to improve accuracy, then measurement accuracy improves, but manufacturing difficulty and cost increase significantly
Solution Approach 1:
The electrode design changes the geometric parameters of the transmitting electrodes from uniform rectangular shapes to trapezoidal shapes with specific width variations. This parameter change allows the use of standard PCB gap widths (≥0.076 mm) while achieving high measurement accuracy through the trapezoidal profile's ability to create continuous capacitance variation.
3Device complexity
If standard rectangular electrodes are used, then device complexity is reduced, but signal-to-noise ratio deteriorates due to abrupt capacitance changes
Solution Approach 1:
The trapezoidal electrode structures create a dynamic capacitance variation pattern during sliding movement. The varying width of each trapezoidal structure ensures that capacitance changes gradually and continuously as the movable grating plate moves relative to the stationary grating plate, eliminating abrupt transitions that would generate noise and improve signal stability.
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 enhances measurement accuracy and signal-to-noise ratio, reducing non-linear errors and stabilizing measurement data while being compatible with standard PCB fabrication processes.
Implementation Method 1
capacitive grating displacement sensor
Data Source
AI summary
An electrode for a capacitive grating displacement sensor. The electrode includes a movable grating plate and a stationary grating plate. The movable grating plate is slidably mounted on the stationary grating plate. The movable grating plate includes a transmitting electrode. The transmitting electrode includes a plurality of mutually inverted trapezoidal structures. The plurality of trapezoidal structures of the transmitting electrode are disposed at equal intervals along a sliding direction of the movable grating plate. The structure is configured to reduce, or even substantially eliminate, the abrupt non-linear errors that arise when the edges of the insulating grooves between conventional transmitting electrodes align with the edges of the electrodes on the stationary grating. This improvement enables an enhancement in the overall measurement accuracy of a measurement device. Additionally, the proposed electrode improves the signal-to-noise ratio of the electrode coupling, resulting in more stable measurement data.