Impedance Measurement Using Fast Current Pulses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining the impedance of electrically conducting devices, such as batteries and welded connections, face challenges in precision and reproducibility, particularly failing to accurately account for fast-dynamic impedances like inductances due to limitations in temporal resolution and current ramp precision.
Innovation Solution
A method involving a time-varying electric current that rapidly changes between levels, allowing for the identification of a first local voltage extremum and subsequent ohmic resistance voltage, enabling the determination of impedance with high temporal resolution, specifically within microseconds, to analyze both slow and fast-dynamic impedances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant current is applied to determine DC resistance, then the measurement is simple to perform, but the reproducibility is poor and fast-dynamic impedances cannot be captured
Solution Approach 1:
The patent applies periodic current pulses with specific timing characteristics to excite the device under test. By using repeated pulse sequences with controlled width and amplitude, the method captures both fast transient responses and steady-state behavior, enabling reproducible measurement of impedance components that vary with time and frequency
Solution Approach 2:
The patent transitions from static DC resistance measurement to dynamic impedance characterization by applying time-varying current pulses. The measurement system captures the transient voltage response during pulse application and relaxation, enabling separation of inductive, capacitive, and resistive components that remain hidden in static measurements
2Loss of information
If current pulse method is used to obtain detailed impedance values, then more information is gained, but the results are not mathematically unique and fast-dynamic impedances are still missed
Solution Approach 1:
The patent segments the impedance measurement into distinct time-domain components by analyzing voltage responses at different phases of the current pulse sequence. The fast transient response captures inductive effects, the intermediate phase captures capacitive effects, and the steady-state captures resistive effects, allowing unique determination of each impedance component through temporal separation
Solution Approach 2:
The patent adds the time dimension to impedance measurement by capturing voltage responses across multiple time scales during pulse application. This transforms the traditional frequency-domain EIS approach into a time-domain method that resolves overlapping impedance components through their characteristic response times, providing mathematically unique solutions
3Loss of information
If EIS is performed to obtain complex impedance, then detailed frequency-dependent information is obtained, but the measurement takes several seconds and requires LTI system behavior
Solution Approach 1:
The patent replaces the traditional frequency-sweep approach of EIS with a time-domain pulse excitation method. By applying current pulses and capturing the transient voltage response, the system obtains equivalent impedance information without requiring multiple frequency measurements, reducing measurement time from seconds to microseconds while maintaining accuracy for non-LTI systems
4Measurement precision
If high temporal resolution is used to capture fast-dynamic impedances, then inductive overshoot is visible, but the sample rate requirements are too high for state-of-the-art apparatus
Solution Approach 1:
The patent applies current pulses with widths and amplitudes optimized to produce measurable inductive overshoot within the capabilities of standard apparatus. By controlling the pulse parameters to generate sufficiently large transient responses, the method achieves effective measurement of fast-dynamic impedances without requiring excessively high sample rates beyond conventional equipment capabilities
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 allows for precise and reproducible impedance determination, including ohmic and inductive components, overcoming the limitations of existing methods by providing detailed and unique results with high informational content.
Implementation Method 1
a voltage response to the applied current change of the electrically conducting device at the terminals exhibits a first local voltage extremum, such as a peak, particularly at the time point, at which the applied current reaches the second level, particularly due to an inductive overshoot
Implementation Method 2
an ohmic resistance voltage, i.e. a voltage mainly caused by ohmic resistances is adopted by the voltage response, when the first local voltage extremum has decayed
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to a method for determining an impedance of an electrically conducting device (11), such as a battery or a welded metal joint, comprising the steps of: - applying a time-varying electric current (301) to the electrically conducting device (11), wherein the current (301) varies at least between a first level (31, 311) and a second level (33, 331), wherein the current (301) changes between the first level (31, 311) and second level (33, 331) within a time interval (302), wherein said time interval (302) is so short that a voltage response (39) of the electrically conducting device (11) exhibits a first local voltage extremum (36, 361) followed by a decay (364), wherein an ohmic resistance voltage (342) is adopted by the voltage response (39), when the first local voltage extremum (36, 361) has decayed, - acquiring the voltage response (39) at least partially, - determining an impedance of the electrically conducting device (11) from the acquired voltage response (39).