Multi-Range Current Measurement Using Electronic Bypass
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Solution Overview
Problem
Existing current measurement systems face challenges in rapidly switching between ranges without glitches and minimizing insertion impedance, especially on low ranges, while ensuring accurate and reliable measurement of unknown electrical currents.
Innovation Solution
The system employs multiple low-range current gauges with bypass mechanisms and arithmetic units to calculate intermediate values, allowing for seamless range selection and minimal impedance insertion, using trans-impedance units and sense amplifiers to provide accurate current measurements across a wide range of currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If automatic range selection is implemented using relays or switching transistors, then range switching is automated, but switching glitches and settling time issues occur
Solution Approach 1:
The patent replaces mechanical relay-based switching with an electronic current bypass mechanism using FETs and operational amplifiers. The high-current sensor circuit directly bypasses excess current to ground through a controlled current path, eliminating mechanical contact and associated switching glitches. This substitution of mechanical switching with electronic current control resolves the reliability issue while maintaining automation.
Solution Approach 2:
The patent introduces an intermediary current bypass path controlled by FETs Q1 and Q2 that分流 (diverts) excess current before it reaches the low-current sensor. This intermediary mechanism prevents the switching transistor itself from handling the full switching current, reducing stress and improving switching stability. The bypass circuit acts as a mediator that protects the main switching element.
2Adaptability or versatility
If shunt resistance is increased to measure lower currents, then measurement range is extended, but insertion impedance increases and affects circuit operation
Solution Approach 1:
The patent segments the current measurement function into two independent parallel paths: a high-current sensor path with low shunt resistance (0.01 ohms) and a low-current sensor path with high shunt resistance (1.0 ohms). Each path is optimized for its specific current range. The switching mechanism selectively activates only the appropriate path, allowing the system to use low impedance for high currents and high impedance for low currents without compromise, thus resolving the contradiction between measurement range and insertion impedance.
Solution Approach 2:
The patent implements dynamic switching between different sensor circuits based on the magnitude of the input current. The system automatically adjusts which measurement path is active, transitioning from the high-current low-impedance path to the low-current high-impedance path as needed. This dynamic adaptation allows the system to maintain optimal impedance characteristics for the current being measured, resolving the static contradiction between range and impedance.
3Device complexity
If manual shunt substitution is used, then device complexity is reduced, but measurement time and operator skill requirements increase
Solution Approach 1:
The patent implements a self-service automatic range selection system where the measurement device itself automatically determines and switches to the appropriate current range without operator intervention. The system monitors the input current magnitude and autonomously selects the appropriate sensor circuit (high-current or low-current path), eliminating the need for manual shunt substitution. This self-service capability reduces measurement time while the integrated circuit implementation keeps overall device complexity manageable.
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 enables rapid, glitch-free switching between measurement ranges with minimal impedance insertion, providing accurate and reliable current measurements across a wide range of currents, improving the efficiency and precision of current measurement systems.
Implementation Method 1
measuring the voltage drop V across the shunt, and converting the measured voltage to amperes (amps) by application of Ohm's Law: I=V/R
Implementation Method 2
measuring the voltage drop V across the shunt, and converting the measured voltage to amperes (amps) by application of Ohm's Law: I=V/R
Implementation Method 3
a bipolar current bypass consisting of FETs Q1 and Q2 that together shunt the current being measured to ground when the magnitude of that current exceeds the range of the low-current sensor
Data Source
AI summary
An electrical current measurement system. A first low-range current gauge receives a current to be measured and provides a first intermediate value indicative of the amplitude of the current up to a first maximum current. A second low-range current gauge receives any portion of the current having a magnitude that exceeds the first maximum current and provides a second preliminary value indicative of the amplitude of the portion of the current having a magnitude that exceeds the first maximum current up to a second maximum current. An arithmetic unit or a digital processor receives the first intermediate value and the second preliminary value and provides a second intermediate value indicative of the amplitude of the current. A full-range current gauge may also be provided. A selector or the digital processor selects one of the values for display or other output.