Skin Impedance Measurement with Forward and Reverse Voltage Correction
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Solution Overview
Problem
Conventional skin impedance measurement methods using DC constant voltage or current sources face reliability and reproducibility issues due to electrode polarization, biopotential in biological tissues, lack of measurement standards, and heterogeneous tissue structure, leading to distorted results.
Innovation Solution
A skin impedance measurement device with an adjustable DC voltage output unit generating step-function DC voltages, allowing for forward and reverse voltage applications between electrodes to assess and correct for polarization effects, ensuring accurate measurements by calculating arithmetic and geometric averages when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If DC constant voltage or current sources are used for skin impedance measurement, then the measurement process is simple, but the measurement results are distorted due to electrode polarization and biopotential effects
Solution Approach 1:
The patent applies periodic square wave voltages with alternating polarities (forward and reverse directions) to the skin. This periodic action with varying polarity helps to minimize electrode polarization effects and biopotential interference by continuously reversing the electrical field direction, thereby obtaining more accurate skin impedance measurements while maintaining operational simplicity
Solution Approach 2:
The patent changes the voltage polarity parameter by applying voltages in both forward and reverse directions. This parameter change allows the system to compensate for polarization effects and biopotential interference dynamically, improving measurement accuracy without significantly complicating the measurement process
2Measurement precision
If forward and reverse voltages are applied to correct polarization effects, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The measurement device generates periodic square wave voltages with alternating polarities through a voltage source connected to the electrodes. This periodic application of forward and reverse voltages corrects polarization effects and biopotential interference, improving measurement accuracy while using a relatively simple circuit configuration that does not require complex additional hardware
Solution Approach 2:
The system measures skin impedance values obtained from both forward and reverse voltage applications and uses these measurements to calculate corrected skin impedance values. This feedback-based calculation approach improves accuracy by compensating for polarization effects without requiring complex real-time adjustment mechanisms in the hardware
3Reliability
If multiple voltage magnitudes and time durations are used to minimize polarization, then measurement reliability is improved, but measurement time increases
Solution Approach 1:
The patent applies periodic square wave voltages with alternating polarities in a systematic sequence of forward and reverse directions. This periodic action with controlled duration minimizes polarization effects and improves measurement reliability while maintaining relatively short measurement times by efficiently utilizing the voltage reversal mechanism
Solution Approach 2:
The system varies voltage magnitude and application time duration as controlled parameters to optimize the balance between minimizing polarization effects and keeping measurement time acceptable. By adjusting these parameters systematically, the patent achieves reliable measurements without excessive time consumption
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 enhances the reliability and accuracy of skin impedance measurements by minimizing polarization effects and providing a more precise estimation of skin impedance, even in abnormal conditions, while ensuring safe current levels through a protective resistor.
Implementation Method 1
an adjustable DC voltage output unit configured to generate step-function DC voltages, which is transmitted through electrodes to form forward or reverse voltages on a local skin area
Implementation Method 2
a skin impedance measurement unit configured to measure an electrical signal from a measurement point, thereby obtaining skin impedance
Implementation Method 3
a processor configured to: calculate a difference between the forward skin impedance and the reverse skin impedance; determine, based on continuously measured forward skin impedance, reverse skin impedance, and their difference, whether measurement results are abnormal
Implementation Method 4
applying additional AC voltages of adjustable frequencies and magnitudes
Implementation Method 5
ensuring safe current levels through a protective resistor
Data Source
AI summary
A skin impedance measuring device and method includes: an electrode system having at least two electrodes placed on the skin; an adjustable voltage output unit to generate forward and reverse voltages on the electrodes; a skin impedance measurement unit to measure electrical signals from the electrodes; a central processing unit and a computing memory for calculating forward and reverse skin impedances, determining whether the measurement results are abnormal, and correcting abnormal results by delivering additional DC or AC voltages of adjustable magnitudes and frequencies based on impedances; and a display unit.