ECG Calibration via Injection Electrode Noise Reduction
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Solution Overview
Problem
Electrocardiograph (ECG) measurements are prone to noise interference due to low-level signals and high impedance sources, leading to inaccurate readings, especially in noisy environments.
Innovation Solution
A method and apparatus that inject a known calibration signal into a subject via an injection electrode, measure output signals from input electrodes, derive weighting factors based on the comparison of calibration and output signals, and apply these factors to physiological signals to generate corrected signals, reducing noise interference and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ECG measurements are taken from low-level signals with high impedance sources, then physiological signal acquisition is achieved, but noise interference increases and measurement accuracy deteriorates
Solution Approach 1:
The system performs preliminary calibration by injecting a known test signal through the pedestal ground before actual ECG measurements. This preliminary action characterizes the impedance of each electrode and the protective circuit, allowing the system to pre-calculate correction factors that compensate for noise and interference during subsequent measurements
Solution Approach 2:
The system uses feedback by measuring the actual response to the injected test signal, comparing it with the expected response, and using this information to calculate correction factors. These correction factors are then applied to subsequent measurements to compensate for identified interference and improve accuracy
Solution Approach 3:
A pedestal ground is introduced as an intermediary element that provides a common reference point for signal injection and measurement. This intermediary allows the system to characterize electrode impedances and calculate correction factors without directly interfering with the patient's body, while still enabling accurate noise compensation
2Measurement precision
If a pedestal ground is directly coupled to the patient for test signal injection, then signal characterization is improved, but patient safety and comfort may be compromised
Solution Approach 1:
The system applies a low-amplitude test signal that is sufficient to characterize electrode impedance and calculate correction factors, but low enough to be imperceptible to the patient and safe. This partial action achieves the necessary measurement precision without excessive signal injection that would compromise patient comfort or safety
Data Source
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AI summary
A method for acquiring electrical signals from a living subject, including injecting, via an injection electrode attached to the subject, a known calibration signal to the subject and measuring respective levels of output signals generated at input electrodes attached to the subject in response to the calibration signal. The method further includes deriving respective weighting factors for the input electrodes in response to the respective levels, and applying the respective weighting factors to physiological signals acquired by the input electrodes, so as to generate respective corrected physiological signals.