Parallel Sense Resistor Array for EIS Current Measurement
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Solution Overview
Problem
Current systems for measuring current through electrochemical cells face challenges with high current ratings, where the energy dissipated in shunt resistances increases exponentially, leading to costly and inaccurate measurements due to inductance effects, especially when dealing with large currents.
Innovation Solution
A current measurement system utilizing a parallel arrangement of multiple sense resistors in series with the cell arrangement, along with voltage measurement circuitry and a test current source, allows for accurate calculation of current by measuring voltages across the resistors and summing individual current values, while minimizing inductance effects and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single shunt resistor is used to measure high current, then the current measurement capability is sufficient, but the energy dissipation increases exponentially and inductance effects cause measurement inaccuracy
Solution Approach 1:
The single shunt resistor is segmented into multiple sense resistors connected in parallel. Each resistor handles a portion of the total current, reducing the current through each individual resistor and thereby reducing energy dissipation (P = I²R) while maintaining the same total current measurement capability. The parallel configuration also reduces the equivalent inductance, improving measurement accuracy.
2Measurement precision
If a single shunt resistor is used to measure high current, then the current measurement capability is sufficient, but the cost increases due to high power rating requirements
Solution Approach 1:
The high-power single shunt resistor is replaced by multiple lower-power sense resistors in parallel. Each resistor requires a lower power rating, making them cheaper and more readily available. The cumulative current measurement capability matches the original single resistor while reducing individual component costs and overall system expense.
3Loss of energy
If multiple sense resistors are used in parallel, then the energy dissipation and inductance effects are reduced, but the device complexity increases
Solution Approach 1:
Multiple sense resistors are merged into a single parallel configuration that functions as one equivalent shunt resistor. The voltage measurement circuitry measures the voltage across the parallel combination, and the current is calculated by summing the individual currents through each resistor. This merging approach reduces energy dissipation and inductance while maintaining relatively simple system architecture.
4Device complexity
If a single shunt resistor is used, then the system simplicity is maintained, but the measurement accuracy deteriorates due to inductance effects at high currents
Solution Approach 1:
The single shunt resistor is segmented into multiple parallel sense resistors, each with lower inductance. The parallel configuration reduces the equivalent inductance seen by the measurement circuit, minimizing inductance effects at high currents and improving measurement accuracy while maintaining reasonable system simplicity.
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 precise measurement of high currents with reduced power dissipation and cost, maintaining accuracy by distributing current across multiple resistors and minimizing inductance impact, thus improving the reliability of electrochemical impedance spectroscopy measurements.
Implementation Method 1
voltage measurement circuitry, which can be configured to measure respective voltages across corresponding ones of the sense resistors
Data Source
AI summary
An electrochemical impedance spectroscopy (EIS) current measurement system for measuring a current through a cell arrangement including one or more electrochemical cells can include a parallel arrangement of a plurality of sense resistors, which can be configured to be placed in series with the cell arrangement, and voltage measurement circuitry, which can be configured to measure respective voltages across corresponding ones of the sense resistors.