Electrostatic Encoder Segmented Interdigital Electrodes Noise Reduction
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Solution Overview
Problem
Electrostatic encoders face challenges in reducing noise interference from electronic equipment due to the large area of interdigital electrodes, which affects measurement accuracy, especially when the scale is long compared to the sensor head.
Innovation Solution
The electrostatic encoder design features interdigital electrodes divided by slits to limit the alternating electric field to overlapping regions, and sub-electrodes are used to cancel out voltage offsets, reducing noise influence and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the scale is made long to increase measurement range, then the measurement range is improved, but the noise interference from electronic equipment increases due to the large area of interdigital electrodes
Solution Approach 1:
The interdigital electrodes are divided into multiple independent electrode groups by slits, where each group corresponds to a specific measurement section. This segmentation limits the alternating electric field to localized overlapping regions between corresponding electrode groups on the scale and sensor head, thereby reducing noise interference from electronic equipment while maintaining a long scale for increased measurement range.
2Area of stationary object
If the interdigital electrode area is increased to improve signal strength, then the signal strength is improved, but the noise interference from electronic equipment increases
Solution Approach 1:
The interdigital electrodes are divided into multiple independent electrode groups by slits. Each electrode group maintains sufficient area for adequate signal strength while being spatially separated from other groups. The slits restrict the alternating electric field to localized overlapping regions, preventing noise propagation across the entire electrode area and reducing overall noise interference from electronic equipment.
Solution Approach 2:
Each electrode group is designed to generate alternating electric fields locally in its corresponding overlapping region with the scale. This localized field generation ensures that each electrode group contributes to signal strength in its specific measurement section without creating widespread noise interference, achieving both strong local signals and reduced overall noise.
3Measurement precision
If sub-electrodes are added to cancel voltage offsets, then the measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
Sub-electrodes are integrated with the interdigital electrodes to form a unified electrode structure. The sub-electrodes are positioned adjacent to the interdigital electrodes and share the same segmented grouping and slit configuration. This merging allows the sub-electrodes to cancel voltage offsets generated by the interdigital electrodes without requiring separate, independent electrode structures, thereby improving measurement accuracy while minimizing the increase in device 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
This design enhances measurement accuracy and reduces noise interference, allowing for precise displacement detection with higher resolution and reduced adverse effects on electronic equipment.
Implementation Method 1
a voltage applying portion configured to apply an alternating voltage to the transmitting coupling electrodes
Implementation Method 2
a potential difference detecting portion configured to detect a potential difference between the interdigital electrodes
Data Source
AI summary
An electrostatic encoder comprising receiving coupling electrodes formed on a scale, and extending in a predetermined direction, transmitting coupling electrodes provided on a sensor head, and located to face the receiving coupling electrodes, digital electrodes provided on the scale to extend from the receiving coupling electrodes in a direction perpendicular to the predetermined direction, and arranged at a predetermined pitch, two pairs of interdigital electrodes provided on the sensor head, and located to face the digital electrodes, a voltage applying portion configured to apply an alternating voltage to the transmitting coupling electrodes, and a potential difference detecting portion configured to detect a potential difference between the interdigital electrodes of each of the two pairs of interdigital electrodes. The two pairs of interdigital electrodes are arranged at the same pitch, and the each pair of interdigital electrodes are spaced apart from each other by a predetermined distance in the predetermined direction.