Open Circuit Detection via Virtual Ground and FFT Analysis
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Solution Overview
Problem
Existing circuit detection systems face challenges in accurately determining the status of an object circuit due to noise interference from various circuit elements, particularly in AC systems where large equivalent resistance generates significant noise, and in DC systems where long grounding wires reduce voltage and increase noise, leading to inaccurate results.
Innovation Solution
An open circuit detecting system that utilizes a virtual ground induced by characteristic impedance of a parasitic capacitor to determine the circuit status by testing and amplifying the capacitance of the parasitic capacitor, employing a test unit, sampling unit, and signal processing unit to generate and process electrical signals, which indicates whether the circuit is open based on capacitance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If AC detecting system uses filter module to eliminate noise, then noise interference is reduced, but desired frequency signals may also be removed causing loss of detection features
Solution Approach 1:
The patent replaces the traditional mechanical/electrical filtering approach with a signal processing method based on frequency domain analysis. Instead of using physical filter modules that selectively block frequencies, the system uses Fast Fourier Transform (FFT) to convert time-domain signals into frequency-domain representations, allowing digital separation of noise and useful signals based on their spectral characteristics without physically removing any frequency components
Solution Approach 2:
The patent changes the parameter space from time-domain filtering to frequency-domain analysis. By transforming the detection approach to operate in the frequency domain through FFT, the system can identify and analyze signals at specific frequencies (including non-integer multiples of fundamental frequency) while filtering out noise based on spectral density, rather than using time-domain filtering that loses frequency information
2Measurement precision
If DC detecting system increases voltage amplitude and sampling resolution to ensure accuracy, then measurement precision improves, but system complexity and cost increase
Solution Approach 1:
The patent replaces hardware-based precision enhancement (high-voltage amplifiers, high-resolution ADCs) with software-based signal processing. By using FFT and spectral analysis algorithms, the system can achieve high measurement precision with standard voltage levels and conventional sampling resolution, as the frequency-domain processing extracts precise information without requiring analog signal conditioning
Solution Approach 2:
The patent creates a digital copy of the signal in the frequency domain through FFT transformation. This digital representation preserves all the information from the original time-domain signal while allowing noise-free analysis and measurement, eliminating the need for complex analog signal conditioning hardware
3Measurement precision
If AC detecting system increases signal frequency to compensate for low capacitance, then detection sensitivity improves, but signal degradation occurs due to parasitic capacitance and loop impedance
Solution Approach 1:
The patent replaces time-domain impedance-based detection with frequency-domain capacitive coupling detection. By using FFT to analyze the frequency spectrum of the signal after capacitive coupling, the system can accurately detect capacitance values without being affected by resistive losses or impedance mismatches that plague traditional time-domain methods, especially at higher frequencies
Solution Approach 2:
The patent employs periodic square wave excitation signals to drive the capacitive coupling under test. This periodic action creates distinct frequency components in the response signal that can be easily identified and analyzed using FFT, allowing for reliable detection even when the signal amplitude is small or degraded by parasitic effects
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 approach effectively filters out noise and accurately determines the open circuit status by leveraging the capacitance differences between normal and open circuits, providing reliable results without degrading the AC signal or increasing system noise.
Implementation Method 1
getting an electrical signal through a virtual ground induced by characteristic impedance of a parasitic capacitor
Implementation Method 2
testing the capacitance of the parasitic capacitor and determining whether the object circuit is open
Data Source
AI summary
An open circuit detecting system configured to connect to an object circuit for getting an electrical signal through a virtual ground induced by characteristic impedance of a parasitic capacitor and determining whether the object circuit is open according to the electrical signal.