Current Sensor Impedance Matching for Signal Integrity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The current sensor attenuates the amplitude of the output signal significantly due to its configuration using a 4Ω resistor for voltage conversion, which is not compatible with the characteristic impedance of coaxial cables, leading to signal disturbances and reduced transmission efficiency.
Innovation Solution
A current sensor with a constant impedance filter connected to the coil, limiting the frequency range of the detection current and outputting it through a transmission path with a predetermined characteristic impedance, and a terminating resistance to convert the current to voltage without attenuation, matching the impedance from the input terminal to the terminating resistance with the cable's characteristic impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a 4Ω resistor is used for voltage conversion in the current sensor, then the detection function is achieved, but the signal amplitude is significantly attenuated due to impedance mismatch with the 50Ω coaxial cable
Solution Approach 1:
The patent introduces a constant impedance filter as an intermediary component between the coil and the transmission path. This filter acts as a mediator that transforms the low impedance (4Ω) output from the coil into a high impedance (50Ω) signal suitable for coaxial cable transmission, thereby preventing signal attenuation and enabling efficient energy transfer without direct impedance mismatch
Solution Approach 2:
The patent changes the impedance parameter from 4Ω to 50Ω through the constant impedance filter. By transforming the electrical parameter (impedance) to match the transmission medium, the system achieves maximum power transfer and prevents signal loss during transmission through the coaxial cable
2Object-affected harmful factors
If a T filter with inductors and capacitors is used for noise filtering, then high-frequency noise is removed, but parasitic capacitance causes resonance and distorts the signal waveform
Solution Approach 1:
The patent extracts and removes the problematic T filter configuration from the system. By eliminating the inductors and capacitors that cause parasitic resonance, the design avoids waveform distortion while still achieving noise filtering through the constant impedance filter approach, which does not introduce the same resonant issues
Solution Approach 2:
The patent converts the harmful effect of parasitic capacitance by using a different filtering approach. Instead of using traditional LC filters that exacerbate resonance, the constant impedance filter is designed to work with the parasitic capacitance present in the system, transforming what would be a harmful resonance effect into a benign or even beneficial characteristic that does not distort the signal
3Adaptability or versatility
If the impedance of the filter is not matched to the characteristic impedance of the transmission path, then filtering flexibility is maintained, but signal reflections and disturbances occur in the transmitted waveform
Solution Approach 1:
The constant impedance filter is designed to serve multiple functions simultaneously: it provides noise filtering while maintaining constant impedance matching to the transmission path. This multi-functionality ensures that the filter not only removes noise but also prevents signal reflections and disturbances by maintaining impedance continuity throughout the signal path
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 suppresses parasitic capacitance-induced resonance, allowing for constant amplitude transmission of the detection current with minimal attenuation of base frequency components and effective noise elimination, resulting in a favorable signal-to-noise ratio for precise current measurement.
Implementation Method 1
a coil that is wound around the magnetic core, has one end connected to a reference potential-side, and outputs, from another end, a detection current with a current value in keeping with a current value of a measured current flowing in the measured object inserted through the magnetic core
Data Source
AI summary
A signal is outputted via a transmission path with little attenuation while eliminating high-frequency noise. A current sensor includes: a coil wound around a magnetic core through whose interior a measured electrical path is inserted, is connected to ground at one end, and outputs a current with a current value in keeping with a current value of a measured current flowing on the measured electrical path; a constant impedance filter whose input terminal is connected to another end of the coil, limits a frequency range of the current inputted from the input terminal to a desired frequency range, and outputs the detection current from an output terminal; a transmission path that is directly connected at one end to the output terminal; and a terminating resistance that is connected between another end of the transmission path and ground and converts the current flowing via the transmission path to a detection voltage.