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String galvanometer


The string galvanometer, also known as the Einthoven galvanometer, invented around 1901 by Dutch physician Willem Einthoven was the first practical electrocardiograph (ECG); it was one of the earliest instruments capable of detecting and recording the very small electric currents produced by the human heart and produced the first reliable electrocardiograms. The original machines achieved "such amazing technical perfection that many modern day electrocardiographs do not attain equally reliable and undistorted recordings". Einthoven was awarded the 1924 Nobel prize in Physiology or Medicine for his work.

Previous to the string galvanometer, scientists were using a machine called the capillary electrometer to measure the heart’s electrical activity, but this device was unable to produce results of a diagnostic level.Willem Einthoven invented the string galvanometer at Leiden University in the early 20th century, publishing the first registration of its use to record an electrocardiogram in a Festschrift book in 1902. The first human electrocardiogram was recorded in 1887, however it was not until 1901 that a quantifiable result was obtained from the string galvanometer. In 1908, the physicians Arthur MacNalty, M.D. Oxon, and Thomas Lewis teamed to become the first of their profession to apply electrocardiography in medical diagnosis. Einthoven was awarded the Nobel prize in Physiology or Medicine in 1924 for his work.

Einthoven's invention consisted of a very long (several metres) silver-coated quartz filament of negligible mass that conducted the electrical currents from the heart. This filament was acted upon by powerful electromagnets positioned either side of it, which caused sideways displacement of the filament in proportion to the current carried due to the electromagnetic field. The movement in the filament was heavily magnified and projected through a thin slot onto a moving photographic plate.


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