String galvanometer

[1] Submarine cable telegraph systems of the late 19th century used a galvanometer to detect pulses of electric current, which could be observed and transcribed into a message.

In 1892 André Blondel described the dynamic properties of an instrument that could measure the wave shape of an electrical impulse, an oscillograph.

In 1901, Willem Einthoven described the science background and potential utility of a string galvanometer, stating "Mr. Adair has already built an instrument with a wires stretched between poles of a magnet.

[6] 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.

[7] Willem Einthoven adapted 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.

[citation needed] Einthoven's galvanometer consisted of a silver-coated quartz filament of a few centimeters length (see picture on the right) and negligible mass that conducted the electrical currents from the heart.