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Measurement of Electrical Potentials and Magnetic Fields from the Body Surface
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
Einthoven went on to modify a string galvanometer, previously invented to receive telegraph signals in 1897 by a French engineer, Clement Ader. In 1901, Einthoven used his string galvanometer to measure the ECG. His first string galvanometer had a huge, heavy magnet, in the airgap of which ran a thin silk string under tension, made conductive by rubbing with powdered silver. The ends of the string were connected to wires that led to two, saline-filled jars in which the patient immersed either two hands, or a hand and a foot. The low impedance of the saline jar electrodes allowed a relatively large action current to flow through the galvanometer string. The solenoidal magnetic field surrounding the current-carrying string interacts with the linear magnetic field in the magnet's air gap, and the string experiences a differential force along its length given by the vector cross-product: dF=Idl×Bnewtons.
Investigating the performance of dry textile electrodes for wearable end-uses
Published in The Journal of The Textile Institute, 2019
Xiang An, Orathai Tangsirinaruenart, George K. Stylios
Electrodes for measuring biopotential have been studied since 1903, when the first string galvanometer for electrocardiogram (ECG) recording was invented. With advances of ECG recording techniques, many types of electrodes have been designed to meet different requirements. The textile-based electrode is one of these and it was first introduced for ECG monitoring by Ishijima (1997), who made part of a bed sheet with electrically conductive yarn to monitor ECG while the subject was sleeping. Many researchers have been working since then on many textile electrode types and much effort has been spent to improve their performance (Donnelly et al., 2013; Pola & Vanhala, 2007; Zheng, Zhang, Wu, & Zhang, 2007).