The first workable device for recording small potentials was the string galvanometer.

They had taken the string galvanometer and adapted it to record signals from microphones onto photographic film.

Beginning in 1901, Einthoven completed a series of prototypes of a string galvanometer.

Also, its relatively small size compared to the string galvanometer also contributed the widespread of the vacuum tube.

Electromagnetic oscillographs had replaced the Lippman electrometer and the string galvanometer in electrophysiological experiments.

String galvanometer, an instrument that provided the first practical electrocardiogram (ECG)

The first human electrocardiogram was recorded in 1887, however it was not until 1901 that a quantifiable result was obtained from the string galvanometer.

Forbes reported the replacement of the string galvanometer with a vacuum tube to amplify the EEG in 1920.

After his development of the string galvanometer, Einthoven went on to describe the electrocardiographic features of a number of cardiovascular disorders.

An initial breakthrough came when Willem Einthoven, working in Leiden, the Netherlands, used the string galvanometer he invented in 1901.

Berger took a cue from Ukrainian physiologist Pravdich-Neminski, who used a string galvanometer to create a photograph of the electrical activity of a dog's brain.

In the 1920s, the way to electrically amplify the cardiac signals was introduced, using vacuum tubes, which quickly replaced the string galvanometer that amplified the signal mechanically.

The string galvanometer was a type of mirror galvanometer so sensitive that it was used to make the first electrocardiogram of the electrical activity of the human heart.

The electrocardiography did not have a practical usability until Willem Einthoven, a Dutch physiologist, coined the way to use the string galvanometer in cardiac signal amplification.

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.

This device was much more sensitive than both the capillary electrometer Waller used and the string galvanometer that had been invented separately in 1897 by the French engineer Clément Ader.

From 1906, he corresponded with the Dutch physiologist Willem Einthoven concerning the latter's invention of the string galvanometer and electrocardiography, and Lewis pioneered its use in clinical settings.

He then switched to the string galvanometer and later to a double-coil Siemens recording galvanometer, which allowed him to record electrical voltages as small as one ten thousandth of a volt.

Willem Einthoven invented at Leiden University the string galvanometer in the early 20th century, publishing the first registration of its use to record an electrocardiogram in a Festschrift book in 1902.

Essentially the string galvanometer consisted of a coil of copper wire, connected at either end to two electrodes, and string hanging down within the coil to which was attached a small magnetized mirror.

In Wedensky's laboratory, and at the same time as Charles S. Sherrington (1857-1952), Beritashvili used the string galvanometer to study the central coordination of spinal reflexes in the registration of action currents of antagonist muscles.