Impedance Tomograph Connection Unit Overvoltage Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing impedance tomography systems face challenges in protecting against overvoltage damage from defibrillators without compromising the effectiveness of defibrillation, as conventional protective measures are either ineffective or overly complex and costly, particularly when integrated into flexible electrode carriers with multiple skin electrodes.
Innovation Solution
A connection unit with detachable and releasable contact devices, each equipped with overvoltage protection circuits, is used to connect impedance tomographs to skin electrodes, allowing for compact and flexible placement while minimizing the length and cost of electrical connections, thereby effectively shielding the system from high voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protective measures (varistors or diodes) are connected in parallel to the input amplifier, then overvoltage protection is improved, but parasitic capacitance increases causing unacceptable reactances at operating frequencies
Solution Approach 1:
A capacitor is introduced as an intermediary element between the defibrillator and the impedance tomograph. This capacitor acts as a mediator that allows the defibrillator pulse to pass through while blocking the harmful overvoltage from reaching the sensitive input amplifier, thus protecting the system without adding parasitic capacitance in parallel with the amplifier input
Solution Approach 2:
The protective function is segmented from the main input amplifier circuit. Instead of having protection circuitry integrated directly at the amplifier input (which would add parasitic capacitance), the protection is divided into separate stages: the capacitor handles the defibrillator pulse isolation, while the amplifier remains clean and unaffected by protective components
2Reliability
If protective resistors with high resistance values are used to protect the impedance tomograph, then overvoltage protection is improved, but the effectiveness of defibrillation is excessively restricted
Solution Approach 1:
The capacitor serves as an intermediary that differentiates between the two types of electrical signals: it blocks the high-voltage defibrillator pulse from reaching the amplifier while allowing the low-amplitude measurement signals to pass through freely, thus protecting the system without impeding the defibrillation function
Solution Approach 2:
The protective solution changes the parameter of impedance protection dynamically - the capacitor presents high impedance to the high-voltage defibrillator pulse (blocking it) but maintains low impedance to the low-voltage measurement signals (allowing them through), thus protecting against overvoltage without restricting defibrillation effectiveness
3Reliability
If a central protective circuit is integrated into the electrode carrier, then overvoltage protection is improved, but the flexibility and ease of placement of the electrode carrier is reduced
Solution Approach 1:
The protective function is extracted from the electrode carrier structure itself and placed in the connection unit between the electrode carrier and the impedance tomograph. This extraction allows the electrode carrier to remain simple, flexible, and easy to place on the patient, while the protection function resides in the detachable connection unit
4Reliability
If electrical connections are extended to connect multiple skin electrodes to a central protective circuit, then overvoltage protection is improved, but the length and cost of electrical connections increase
Solution Approach 1:
The protective circuit is extracted from the electrode carrier and placed in the connection unit, eliminating the need for long electrical connections within the electrode carrier itself. The protection function is now located at the connection point to the impedance tomograph, minimizing connection lengths
Solution Approach 2:
The protective function is segmented and assigned to individual contact devices rather than requiring a central protective circuit that would need long connections to all electrodes. Each contact device can have its own protection, reducing overall connection length and complexity
Data Source
Figure 1
AI summary
The invention relates to a connection unit (1), by means of which an impedance tomograph (3) can be connected to a first and a second skin electrode (6, 8) of an electrode carrier (4), wherein the skin electrodes (6, 8) are arranged on the electrode carrier (4) at a distance from each other and in the longitudinal direction L of the electrode carrier (4), and wherein a first counter-contact device (24) is arranged on the electrode carrier (4) and connected to the first skin electrode (6), a second counter-contact device (26) is arranged on the electrode carrier (4) and connected to the second skin electrode (8), the connection unit (1) comprising a first and a second contact device (16, 18), the first contact device (16) being releasably connectable to the first counter-contact device (24), the second contact device (18) being releasably connectable to the second counter-contact device (26), and the first and the second contact device (16, 18) have in each case one electrical protection circuit (10, 12). The invention further relates to a system for an electrical impedance tomograph (3), wherein the system comprises a connection unit (1) according to the invention.