Patient Potential Detection Device with Impedance Feedback
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Solution Overview
Problem
Existing devices for detecting electric potentials on patients face challenges due to capacitive coupling with surrounding electric fields, leading to common mode signals that overlay and obscure the useful signals, and poor contact impedance between electrodes and skin, resulting in noisy or unusable measurements.
Innovation Solution
A device with a potential output connected to a current-measuring device, where the mean value signal and current signal are used to calculate impedance, allowing continuous monitoring and detection of contact impedance changes, and implementing the Driven-Right-Leg and reference amplifier principles to reduce common mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional electrode is connected to equate patient and device ground potentials, then the potential difference between patient and device is reduced, but a common mode signal is generated due to contact impedance that overlays and obscures the useful signal
Solution Approach 1:
The patent implements a feedback mechanism by measuring the common mode signal at the additional electrode and feeding back an inverted version of this signal through the potential output. This negative feedback reduces the common mode signal by counteracting it with an equal and opposite signal, thereby minimizing the overlay effect on useful signals while maintaining reliable ground potential reference.
Solution Approach 2:
The patent dynamically adjusts the potential applied to the additional electrode based on the measured common mode signal level. By changing the voltage parameter at the potential output in response to detected signal conditions, the system optimizes the balance between maintaining ground reference stability and minimizing common mode interference on the measurement channels.
2Measurement precision
If amplifiers are used to amplify the useful signal, then the signal strength is increased, but the input dynamic range must be very high to accommodate both the useful signal and the larger common mode signal
Solution Approach 1:
The patent converts the harmful common mode signal into a beneficial element by using it as the basis for the feedback mechanism. The common mode signal, which would normally be harmful by overlaying useful signals, is instead measured and used to generate the compensating feedback signal that actively reduces interference, thereby allowing amplifiers to operate with reduced dynamic range requirements.
Solution Approach 2:
The patent introduces an intermediary feedback path that mediates between the common mode signal generation at the additional electrode and the useful signal measurement channels. This intermediary mechanism processes the common mode signal separately and injects the corrected signal back into the measurement system, allowing the main amplifiers to focus on amplifying useful signals without needing to handle the full dynamic range of common mode interference.
3Ease of operation
If the contact impedance between additional electrode and patient skin is poor, then electrode detachment occurs easily, but noise increases markedly and measured signals become unusable
Solution Approach 1:
The patent implements preliminary monitoring of contact impedance to detect degradation before it causes complete signal failure. By continuously measuring impedance and providing early warning or corrective action, the system prevents the transition from acceptable to unusable signal quality, allowing for proactive electrode replacement or adjustment before noise becomes problematic.
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
Enables reliable detection of contact impedance between electrodes and the patient's skin, reducing noise and improving signal quality by distinguishing and processing the useful signal from common mode interference.
Implementation Method 1
a current-measuring device, which is designed to send a current signal, which is proportional to the current flowing through the potential output
Implementation Method 2
an analyzing unit being provided, which is connected such that a signal corresponding to the signal at the potential output, the signal sent by the summing unit to its output and the signal sent by the current-measuring device are fed to it, and by the analyzing unit being designed to generate an impedance signal from the fed signals
Implementation Method 3
Since the body of the patient is surrounded by electric fields, potentials are formed due to capacitive coupling on the skin of the patient
Data Source
AI summary
A device for detecting electric potentials includes a plurality of measuring inputs (9) for connecting to measuring electrodes (11), which can be placed on the body of a patient (3), a plurality of measuring amplifiers (Op1, . . . , OpN), and a potential output (27) for connecting to an additional electrode (31), which can be placed on the body of the patient (3), to which a preset voltage can be applied. A summing unit (17) sends a signal, which is an indicator of the mean value of the signals sent by the measuring amplifiers (Op1, . . . , OpN). A current-measuring device (29) sends a current signal, which is proportional to the current flowing through the potential output. An analyzing unit (35) is connected to receive a potential output voltage signal, the summing unit output (19) signal and the current-measuring device signal. The analyzing unit is configured to generate an impedance signal from the fed signals.