Bio Impedance Measurement Using Frequency Segmentation
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Solution Overview
Problem
Existing bio impedance measurement technologies face challenges in efficiently measuring bio impedance while minimizing power consumption, particularly due to the need for wide bandwidth amplifiers that increase power consumption and are not optimized for specific frequency bands.
Innovation Solution
The bio impedance measurement apparatus employs an intermediate modulator to reduce the frequency of the input signal, thereby reducing the required bandwidth of the amplifier and power consumption, using a controller to determine optimal frequencies for measurement, and includes a demodulator and filter to selectively measure real and imaginary components of bio impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide bandwidth amplifier is used to measure high-frequency bio impedance, then measurement capability is improved, but power consumption increases
Solution Approach 1:
The frequency measurement range is segmented into multiple bands (first frequency band and second frequency band). The system uses different amplifiers optimized for different frequency ranges, with the first amplifier handling lower frequencies and the second amplifier handling higher frequencies. This segmentation allows each amplifier to operate at optimal efficiency for its designated range, reducing overall power consumption while maintaining full measurement capability.
Solution Approach 2:
The system dynamically switches between different amplifiers based on the frequency of the input signal. A frequency detection unit identifies the signal frequency, and a switch routes the signal to the appropriate amplifier (first or second). This dynamic adaptation ensures that the system uses the most power-efficient amplifier for each measurement condition, resolving the contradiction between measurement capability and power consumption.
2Measurement precision
If a single high-performance amplifier is used to cover all frequency bands, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
Instead of using one complex amplifier designed to handle all frequency bands, the system segments the amplification function across multiple specialized amplifiers. Each amplifier is optimized for a specific frequency range, resulting in simpler individual designs that collectively provide comprehensive coverage. This segmentation maintains measurement accuracy while reducing the complexity of any single amplifier component.
Solution Approach 2:
A frequency detection unit and switching mechanism act as intermediaries between the input signal and the amplifiers. These intermediary components manage the signal routing based on frequency, allowing the system to use multiple specialized amplifiers without requiring any single amplifier to handle the full frequency spectrum. This intermediary layer simplifies the overall system architecture by decoupling the frequency-dependent routing from the amplification function.
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 accurate bio impedance measurement with reduced power consumption by amplifying only the necessary frequency band, enhancing the efficiency of the measurement process and enabling the measurement of high-frequency bio impedance with lower bandwidth amplifiers.
Implementation Method 1
providing an alternating current having a first frequency to a living body
Implementation Method 2
modulating the voltage signal generated between the two terminals of the contactor using a second frequency
Implementation Method 3
demodulating the amplified voltage signal using a third frequency to generate a demodulated voltage signal
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A bio impedance measurement apparatus includes a current applicator configured to provide, to terminals contacting a body, a current based on a first control signal, and a modulator configured to modulate a voltage generated as the current flows through the body, based on a second control signal. The apparatus further includes an amplifier configured to amplify the modulated voltage, and a demodulator configured to demodulate the amplified voltage based on a third control signal.