Capacitance Detection Device Shield Line Equipotential Circuit

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Solution Overview

Problem

Capacitive sensor devices face reduced measurement accuracy due to noise signals received by long control lines connecting the capacitive sensor and voltage applying or measuring means, leading to deteriorated performance.

Innovation Solution

A capacitance detection device with a shield line electrically shielding the control line and an equipotential circuit that sets the potential of the shield line equal to the control line, reducing the influence of parasitic capacitance and enhancing measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the control line is made long to connect the capacitive sensor and voltage applying means when arranged apart, then the spatial flexibility is improved, but the measurement precision deteriorates due to noise signal reception

Engineering Contradiction:

Improvespatial flexibilityVSAvoidcapacitance measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

A shield line is introduced as an intermediary element between the control line and external noise sources. The shield line acts as a mediator that blocks electromagnetic noise from coupling into the control line, thereby protecting the measurement signal while allowing the control line to maintain its required length for spatial flexibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The shield line is connected to ground potential to create an equipotential barrier. By maintaining the shield line at a constant ground potential, voltage fluctuations and noise signals are prevented from coupling into the control line, thus preserving measurement precision while allowing the control line to be extended for spatial adaptability.

Inventive Principle:

Principle #12Equipotentiality

2Measurement precision

If the shield line is added to reduce noise interference, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:

Improvecapacitance measurement accuracyVSAvoidcircuit structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The shield line is implemented as a thin conductive layer or foil that can be easily integrated around or alongside the control line. This thin-film approach provides effective electromagnetic shielding while adding minimal structural complexity and occupying minimal space in the circuit design.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The shield line is nested around the control line in a coaxial or spiral configuration, with the shield line forming an outer layer that encloses the inner control line. This nested arrangement provides effective shielding while utilizing compact spatial relationships that minimize additional circuit complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Object-affected harmful factors

If the shield line is used for electrical shielding, then the noise resistance is improved, but the charge accumulation on parasitic capacitance increases

Engineering Contradiction:

Improvenoise resistanceVSAvoidcharge accumulation on parasitic capacitance

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The parasitic capacitance of the shield line is extracted and connected directly to ground through a dedicated low-impedance path. By providing this separate discharge path, charge accumulation on the parasitic capacitance is prevented, allowing the shield line to maintain its noise shielding function without generating harmful charge buildup that could interfere with measurements.

Inventive Principle:

Principle #2Taking out (Extraction)

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 effectively reduces the impact of charge accumulation on parasitic capacitance, enabling accurate capacitance measurement by maintaining the potential of the shield line equal to the control line, thus improving measurement precision.

Implementation Method 1

a shield line electrically shielding the control line

Methodology Applied

Scientific EffectElectrical shielding: Faraday Cage

Implementation Method 2

an equipotential circuit setting a potential of the shield line equal to a potential of the control line

Methodology Applied

Scientific EffectEquipotential principle:

Implementation Method 3

a sensor element whose capacitance changes, measuring a voltage change of the sensor element when the charging voltage is applied to the sensor element, and detecting the capacitance of the sensor element based on the voltage change

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11448559B2Capacitance detection device for detecting the capacitance of a sensor element

Publication Date: 2022.09.20 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A capacitance detection device includes a sensor unit including at least one sensor element whose capacitance changes, a control line applying to the sensor element a predetermined charging voltage for detecting the capacitance of the sensor element, a shield line electrically shielding the control line, a control circuit supplying the charging voltage to the sensor element via the control line, measuring a voltage change of the sensor element when the charging voltage is applied to the sensor element, and detecting the capacitance of the sensor element based on the voltage change, and an equipotential circuit setting a potential of the shield line equal to a potential of the control line.