Phase-Locked Current Simulation for Fine Impedance Calibration
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Solution Overview
Problem
Existing impedance measurement devices lack flexibility and accuracy in calibrating over a wide range of impedances due to the use of fixed transformer arrangements, which introduce interference and limit granular step resolution.
Innovation Solution
Employing a phase-locked current generator to simulate and present impedance with fine adjustments, allowing for highly accurate and granular calibration by adjusting the amplitude of the second AC signal in increments as low as 1 nanoampere, thereby enabling calibration over a wide range of impedance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed transformer arrangement is used for calibration, then the calibration process is simple to implement, but the flexibility and resolution for testing performance over a wide range of impedances is limited
Solution Approach 1:
The patent replaces the mechanical fixed transformer arrangement with an electronic simulation system using a current source and impedance simulation circuitry. This substitution enables dynamic, software-controlled impedance presentation without physical transformer changes, achieving fine granular steps (e.g., 1 nA current steps) and wide impedance range coverage while maintaining calibration simplicity through digital control.
Solution Approach 2:
The patent changes the calibration approach from fixed physical transformer ratios to dynamically adjustable electrical parameters. By controlling current amplitude and phase electronically, the system can present any impedance value within the measurement range, providing continuous adaptability rather than discrete transformer ratios. This parameter-based control achieves both versatility and manageable complexity.
2Measurement precision
If a fixed transformer arrangement is used for calibration, then the system structure is simple, but the measurement precision and granular step resolution are insufficient
Solution Approach 1:
The patent replaces mechanical transformer arrangements with electronic signal generation and impedance simulation. The current source provides precisely controlled amplitude and phase, enabling measurement precision at the nanoampere level. This electronic substitution eliminates the coarse discrete steps inherent in fixed transformer ratios while keeping the system structure manageable through integrated circuitry.
Solution Approach 2:
The patent creates an idealized impedance model through simulation rather than relying on physical transformer arrangements. By copying the electrical behavior of ideal impedances through controlled current sources and measurement circuits, the system achieves high measurement precision without the physical constraints and tolerances of real transformers. This virtual modeling approach delivers fine resolution with controlled complexity.
3Reliability
If external cables and resistors are used for calibration, then the system is easy to assemble, but cable noise and interference introduce measurement errors
Solution Approach 1:
The patent merges the current source, impedance simulation circuitry, and measurement functions into an integrated system. By combining these previously separate components (external cables, resistors, and measurement device) into a unified integrated circuit or module, the system eliminates cable connections and external interfaces that introduce noise and interference. This integration maintains reliability through reduced error sources while managing complexity through modular design.
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 phase-locked current generator provides precise and flexible impedance calibration with reduced interference, achieving a resolution as low as 4.5 microohms/ohms and minimizing errors introduced by cable noise and interference.
Implementation Method 1
The phase-locked current generator generates a second AC signal in response to the first AC signal. The second AC signal is phase-locked with respect to the first AC signal and has the same frequency.
Data Source
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AI summary
A method and apparatus for calibrating an impedance measurement device (100a, 100b, 100c) are provided. The impedance measurement device outputs (502) a first AC signal to a phase-locked current generator (124). The phase-locked current generator generates (504) a second AC signal having a phase that is locked to a phase of the first AC signal and having an amplitude that is representative of a presented impedance having a known impedance value. The phase-locked current generator outputs the second AC signal to the impedance measurement device. The impedance measurement device performs (506) an impedance measurement based on the second AC signal to produce a measured impedance value associated with the presented impedance. The impedance measurement device is calibrated (508) based on the measured impedance value and the known impedance value of the presented impedance.