Capacitive Sensor Shielding for Biomedical Signal Interference
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Solution Overview
Problem
Capacitive sensor systems for measuring biobiological electromagnetic signals are sensitive to external interference and prone to movement artefacts due to changes in electrode capacitance, which affects the accuracy of signals like EEGs and ECGs.
Innovation Solution
A sensor system with additional three-dimensional shielding means surrounding the electrode device and signal processing unit, along with a compact design that minimizes interference by decoupling noise signals and using a highpass filter to isolate dynamic measurement signals, and an integrated analog-to-digital conversion for precise signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If capacitive electrode device is used for measuring biobiological signals, then preparatory work is eliminated and electrical resistance is no longer relevant, but the system becomes sensitive to external electromagnetic interference fields
Solution Approach 1:
The patent implements nested shielding structures where an inner electrode shielding element is placed inside an outer additional shielding means. The inner shielding element surrounds the electrode device while the outer shielding means surrounds both the electrode device and the signal processing device, creating multiple layers of electromagnetic protection similar to nested dolls.
Solution Approach 2:
The patent introduces shielding elements as intermediary structures between the electrode device and external electromagnetic interference fields. These shielding elements act as mediators that block or redirect electromagnetic interference while allowing the desired biobiological signals to pass through to the electrode device.
2Volume of moving object
If electrode device is positioned close to signal processing device for compact design, then spatial proximity is achieved, but parasitic galvanic, capacitive or inductive influences occur
Solution Approach 1:
The signal processing device is nested within the additional shielding means, which in turn surrounds the inner electrode shielding element. This nested arrangement allows compact positioning while maintaining electromagnetic isolation through the intermediate shielding layers.
Solution Approach 2:
The additional shielding means acts as an intermediary barrier between the electrode device and the signal processing device, preventing direct electromagnetic coupling while allowing the devices to be positioned in close spatial proximity for compact design.
3Measurement precision
If electrode capacitance is formed between electrode device and measurement object, then capacitive coupling is achieved, but movement artefacts are superposed on the signal
Solution Approach 1:
The patent employs a feedback circuit that continuously monitors the capacitance between the electrode device and the measurement object. When movement causes capacitance changes, the feedback circuit generates compensating signals to cancel out the resulting movement artefacts from the measured biobiological signals.
Solution Approach 2:
The shielding elements serve as intermediaries that stabilize the electrical environment between the electrode device and measurement object, reducing the impact of movement-induced capacitance variations while maintaining the necessary capacitive coupling for signal detection.
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
The system effectively shields against external electromagnetic interference, reduces movement artefacts, and enhances signal accuracy by ensuring a 'one-way' signal path from the electrode device to the signal processing unit, improving the reliability of biobiological signal measurements.
Implementation Method 1
capacitive measurement of electromagnetic signals having a biobiological origin
Implementation Method 2
additional shielding means for shielding out external electromagnetic interference fields
Data Source
AI summary
The invention relates to a sensor system and several method for the capacitive measurement of electromagnetic signals having a biological origin. Such a sensor system comprises a capacitive electrode device (10), an electrode shielding element (20) which surrounds the electrode device (10) at least in part in order to shield the same (10) from interfering external electromagnetic fields, and a signal processing device (30) for processing electromagnetic signals that can be detected by means of the electrode device (10). According to the invention, additional shielding means (21) three-dimensionally surround the electrode device (10) and the electrode shielding element (20) at least in part in order to block out interfering external electromagnetic fields. The changes in the electrode capacity of the capacitive sensor system are determined with the aid of several methods which particularly use the inventive sensor system in order to take said changes into account when the test signals are evaluated.