Capacitance Sensor Electrode Layout for Directional ESD-Shielded Measurement
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Solution Overview
Problem
Existing measuring instruments face challenges in accurately measuring electrostatic capacitance with high directivity, particularly in specific directions, and in preventing Electrostatic Discharge (ESD) from affecting the operational amplifier.
Innovation Solution
The measuring instrument incorporates a disc-shaped base board with at least one sensor chip that includes a signal electrode, a guard electrode, and a first ground electrode. A circuit board with a radio frequency oscillator and a C/V conversion circuit, including an operational amplifier, is used to generate a voltage signal based on the electrostatic capacitance. The guard electrode and first ground electrode shield the rear side of the signal electrode, while a second ground electrode shields the lower side, allowing for high directivity measurements and ESD suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor chip with signal electrode, guard electrode, and ground electrode is used to measure electrostatic capacitance with high directivity, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sensor chip is segmented into functionally distinct electrodes: signal electrode for measurement, guard electrode for field confinement, and ground electrode for reference. This segmentation enables high directivity measurement by assigning specific roles to each electrode, while the modular design keeps the overall structure manageable.
Solution Approach 2:
Different regions of the sensor chip are assigned different functional qualities: the signal electrode region is optimized for capacitance sensing, the guard electrode region for field control, and the ground electrode region for reference potential. This local differentiation enhances measurement directivity without requiring the entire chip to be overly complex.
2Reliability
If guard electrode and ground electrode are added to shield the signal electrode, then reliability is improved by suppressing ESD, but device complexity increases
Solution Approach 1:
The guard electrode and ground electrode are positioned around the signal electrode to create a protective electromagnetic shield before ESD can affect the operational amplifier. This preemptive shielding structure cushions the sensitive amplifier from voltage spikes and static discharge events, enhancing reliability.
Solution Approach 2:
The guard electrode acts as an intermediary between the signal electrode and the external environment, intercepting and diverting ESD away from the signal path. The ground electrode provides an intermediate reference potential that stabilizes the measurement system against electrostatic interference, protecting the operational amplifier without requiring direct modification of the amplifier itself.
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 enables precise measurement of electrostatic capacitance with high directivity in a specific direction, while effectively suppressing ESD to protect the operational amplifier, thereby enhancing the accuracy and reliability of the measurements.
Implementation Method 1
a C/V conversion circuit configured to generate a voltage signal according to an electrostatic capacitance formed by the signal electrode
Implementation Method 2
a guard electrode disposed on a rear side of the signal electrode while being spaced apart from the signal electrode and extending along the signal electrode, and a first ground electrode disposed on a rear side of the guard electrode
Data Source
AI summary
A measuring instrument according to an exemplary embodiment includes a base board, at least one sensor chip provided on the base board, and a circuit board provided on the base board. The at least one sensor chip includes a sensor unit including a signal electrode having a front surface intersecting the base board in a radial direction, a guard electrode disposed on a rear side of the signal electrode, and a first ground electrode disposed on a rear side of the guard electrode. The at least one sensor chip includes a second ground electrode extending along a lower surface of the sensor unit. A space between the second ground electrode and the sensor unit is filled with an insulating material.