Capacitance Detection Using Inductor Phase Shift
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Solution Overview
Problem
Existing capacitance detection apparatuses, such as those using first-order RC low pass filters, face challenges in achieving sufficient detection accuracy due to small phase differences between variable and reference capacitance elements, leading to insufficient resolution.
Innovation Solution
A capacitance detection apparatus is designed with a parallel circuit configuration that includes a tested body and a resistance element in one series circuit and a reference capacitance and resistance element in another, with an inductor element connected between the nodes to increase phase differences, allowing for more accurate capacitance detection using an alternating current voltage with a specific frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If first-order RC low pass filters are used for capacitance detection, then the circuit configuration is simple, but the phase difference is too small to provide sufficient detection accuracy
Solution Approach 1:
The patent transitions from first-order RC filters to second-order RLC filters, adding the inductor dimension to the circuit. This dimensional change in the filter order transforms the phase difference characteristics, enabling sufficient phase separation for accurate capacitance detection while maintaining practical circuit complexity
Solution Approach 2:
The patent changes the filter parameters by introducing inductors to create second-order RLC filters. This parameter change modifies the frequency response and phase characteristics of the circuits, producing larger phase differences that improve capacitance detection resolution without excessive complexity
2Stability of the object's composition
If there is a small difference between the capacitance of the variable capacitance element and the reference capacitance, then the circuit operation is stable, but the phase difference becomes too small to detect with sufficient accuracy
Solution Approach 1:
The patent uses the resonant characteristics of second-order RLC circuits to amplify the phase difference response. By operating near the resonant frequency of the RLC circuits, small capacitance differences produce significantly larger phase differences, enabling detection while maintaining stable circuit operation
Solution Approach 2:
The patent exploits the dynamic phase response characteristics of second-order RLC filters, where the phase difference varies more sensitively with capacitance changes compared to first-order RC filters. This dynamic behavior enhancement allows detection of small capacitance differences
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 apparatus significantly enhances detection accuracy by increasing phase differences, enabling precise capacitance measurement even with small differences between the tested and reference capacitance elements, and is applicable to optical wavelength selective filters for adjusting gap settings.
Implementation Method 1
an inductor element connected between the first node and the second node and configured to increase a phase difference in the voltage with the specific frequency between the first and second nodes
Data Source
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AI summary
A capacitance detection apparatus is provided with: a parallel circuit in which a first series circuit and a second series circuit are connected in parallel, wherein a tested body and a first resistance element are connected at a first node in the first series circuit, and a reference capacitance element and a second resistance element are connected at a second node in the second series circuit; a power supply circuit configured to apply an alternating current voltage with a specific frequency to the parallel circuit; an inductor element connected between the first node and the second node and configured to increase a phase difference in the voltage with the specific frequency between the first and second nodes; and an output device configured to output an electric signal corresponding to a capacitance of the tested body on the basis of the phase difference.