Bio-impedance Measurement Device Using Negative Capacitance Circuit
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Solution Overview
Problem
Bio-impedance measurement devices face errors due to parasitic capacitance at the electrodes, which affect the accuracy of body composition analysis by coupling probing signals to input capacitance, leading to measurement inaccuracies.
Innovation Solution
A bio-impedance measurement device and method utilizing a negative capacitance circuit to cancel the parasitic capacitance by adjusting the capacitance of the circuit to equalize with the parasitic capacitance, thereby reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrodes with parasitic capacitance are used to connect to the user's body, then the probing signal can be introduced into the body, but part of the probing signal is coupled to the parasitic capacitor causing measurement errors
Solution Approach 1:
The patent applies the 'Blessing in disguise' principle by using a negative capacitance circuit to convert the harmful parasitic capacitance effect into a beneficial cancellation mechanism. The negative capacitance circuit generates an opposing capacitive effect that actively counteracts and cancels the parasitic capacitance of the electrodes, transforming the harmful coupling effect into a neutralized state. This allows the probing signal to be accurately introduced into the body without being diverted by parasitic capacitance, thereby improving measurement precision.
Solution Approach 2:
The patent implements 'Preliminary anti-action' by introducing a negative capacitance circuit that pre-establishes an opposing capacitive effect before the measurement process begins. The negative capacitance is configured to counteract the parasitic capacitance of the electrodes in advance, creating a preliminary counterbalancing effect. This preliminary anti-action ensures that when the probing signal is applied, the parasitic capacitance is already neutralized, preventing measurement errors from occurring in the first place.
2Measurement precision
If the probing signal is introduced into the user's body through electrodes, then body impedance can be measured, but the parasitic capacitor causes part of the signal to be lost
Solution Approach 1:
The patent converts the harmful signal loss caused by parasitic capacitance into a beneficial effect by using a negative capacitance circuit. The negative capacitance actively compensates for the signal diversion effect, transforming the energy loss pathway into a compensated state. This ensures that the full probing signal energy is directed into the body for accurate impedance measurement, rather than being lost to parasitic capacitance.
Solution Approach 2:
The patent employs a feedback mechanism where the negative capacitance circuit continuously monitors and counteracts the effects of parasitic capacitance on the probing signal. The circuit is configured to provide real-time compensation for signal loss, adjusting the capacitive effect to maintain optimal signal transmission into the body. This feedback-based compensation ensures consistent signal delivery and accurate measurement throughout the measurement process.
Data Source
AI summary
A bio-impedance measurement device, for measuring a bio-impedance, includes an electrode; a negative capacitance circuit, coupled to the electrode; a signal generator, configured to input a probing signal into the negative capacitance circuit; a demodulation circuit, coupled to the electrode and the negative capacitance circuit, configured to receive a first response signal related to the probing signal from the negative capacitance circuit and generate a first in-phase signal and a first quadrature-phase signal according to the first response signal, wherein the demodulation circuit and the electrode comprise an input capacitance; and a processor, coupled to the negative capacitance circuit and the demodulation circuit, configured to adjust the negative capacitance circuit to cancel the input capacitance according to the first in-phase signal and the first quadrature-phase signal.