Cascaded Log Amplifier Measuring System for High Dynamic Range Current
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Solution Overview
Problem
Current measurement systems fail to accurately measure high dynamic ranges of current passing through discrete paths without interrupting signal flow and often suffer from signal reflections and noise interference.
Innovation Solution
A measuring system with cascaded stages, including high-gain and low-gain legs, using passive devices like diplexers and directional couplers to filter and amplify signals, and log amplifiers to process signals without distortion, combined with adaptive controllers for noise reduction and bipolar signal conversion, allowing for accurate measurement of large dynamic ranges without interrupting the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current transformer is used to measure current, then the measurement can be performed without interrupting signal flow, but the system cannot render high dynamic ranges with high accuracy
Solution Approach 1:
The measurement system is divided into multiple cascaded stages, each handling a specific portion of the dynamic range. The first stage processes high-level signals while the second stage processes low-level signals, allowing each stage to be optimized for its specific range rather than requiring a single device to handle the entire dynamic range.
Solution Approach 2:
The system transitions from a single-dimensional current transformation approach to a multi-dimensional measurement architecture by combining outputs from multiple stages with different gain levels. This dimensional expansion allows simultaneous coverage of high and low signal levels with high precision in each dimension.
2Measurement precision
If high-gain amplification is used to measure low-level signals, then measurement sensitivity improves, but signal reflections and noise interference increase
Solution Approach 1:
By segmenting the measurement into multiple stages with progressively increasing gain, the system avoids applying high gain to the entire signal chain. Each stage operates with moderate gain, reducing the amplification of noise and reflections while still achieving high overall sensitivity through the cascaded architecture.
Solution Approach 2:
The system performs preliminary signal conditioning and filtering in earlier stages before signals are amplified. This preliminary action prepares the signal in a way that reduces the impact of subsequent amplification on noise and reflections, allowing high sensitivity without proportionally increasing harmful factors.
3Measurement precision
If multiple measurement stages are cascaded to extend dynamic range, then measurement accuracy over high dynamic range improves, but device complexity increases
Solution Approach 1:
The cascaded stages are designed with universal characteristics, using similar circuit topologies and component types that can be replicated across stages. This modular universal design allows the system to achieve extended dynamic range while controlling complexity through reuse of proven designs rather than requiring entirely unique circuitry for each stage.
Solution Approach 2:
The measurement system employs a nested stage architecture where each stage is contained within and builds upon the previous stage. This nesting allows systematic extension of dynamic range by adding stages in a structured manner, where each nested stage contributes a specific portion of the overall dynamic range while sharing common system resources and control mechanisms.
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
Enables accurate and uninterrupted measurement of high dynamic ranges of current, minimizing noise and signal reflections, and providing precise energy flow measurements across a wide range.
Implementation Method 1
A passive device such as a directional coupler may couple power flowing in one direction to multiple stages of the measuring system
Implementation Method 2
The log amplifiers may have a fast rise time and a large dynamic range. The output of the log amplifiers may be equivalent to a predetermined amplification factor times a natural log of the input voltage
Data Source
AI summary
A measuring system includes an input that emulates a bandpass filter with no signal reflections. A directional coupler connected to the input passes the filtered input to electrically isolated measuring circuits. Each of the measuring circuits includes an amplifier that amplifies the signal through logarithmic functions. The output of the measuring system is an accurate high dynamic range measurement.