String galvanometer

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String galvanometer

The String galvanometer was one of the earliest instruments capable of detecting and recording the very small electrical

Electricity

Electricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena such as lightning and static electricity, but in addition, less familiar concepts such as the electromagnetic field and electromagnetic induction....
currents produced by the human heart

Heart

The heart is a muscle organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods....
and provided the first practical Electrocardiogram

Electrocardiogram

An electrocardiogram is a recording of the electricity activity of the heart over time produced by an electrocardiograph, usually in a Non-invasive recording via skin electrodes....
(ECG). The original machines achieved "such amazing technical perfection that many modern day electrocardiographs do not attain equally reliable and undistorted recordings".
History
Previous to the string galvanometer, scientists were using a machine called the capillary electrometer

Electrometer

An electrometer is an electricity instrument for measuring electric charge or electrical potential difference. There are many different types, ranging from historical hand-made mechanical instruments to high-precision electronic devices....
to measure the heart’s electrical activity, but this device was unable to produce results of a diagnostic level.

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Encyclopedia

The String galvanometer was one of the earliest instruments capable of detecting and recording the very small electrical

Electricity

Heart

Electrocardiogram

History

Previous to the string galvanometer, scientists were using a machine called the capillary electrometer

Electrometer

Willem Einthoven

Willem Einthoven was a Dutch Physician and physiology. He invented the first practical electrocardiogram in 1903 and received the Nobel Prize in Medicine in 1924 for it....
invented the string galvanometer in the early 20th century, publishing the first registration of its use to record an electrocardiogram in a Festschrift

Festschrift

In academia, a wikt:festschrift is a book honoring a respected academic and presented during his or her lifetime. The term, borrowed from German language, could be translated as celebration publication or celebratory writing....
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 . He was awarded the Nobel prize in Physiology or Medicine

Nobel Prize in Physiology or Medicine

The Nobel Prize in Physiology or Medicine is awarded once a year by the Swedish Karolinska Institutet. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in Nobel Prize in Physics, Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and Physiology or Medic...
in 1924 for his work.

How the string galvanometer works

Einthoven's invention consisted of a very long silver-coated quartz

Quartz

Quartz is the most abundant mineral in the Earth's continental crust . It is made up of a Crystal structure of silica tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm?....
filament of negligible

Negligible

In engineering, mathematics, physics and similar disciplines, the term negligible refers to the quantities so small that they can be ignored when studying the larger effect....
mass that conducted the electrical currents from the heart. This filament was acted upon by powerful electromagnet

Electromagnet

An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric Current . The magnetic field disappears when the current ceases....
s positioned either side of it, which caused sideways displacement of the filament in proportion to the current carried due to the electromagnetic field

Electromagnetic field

The electromagnetic field is a physical field produced by electric charge. It affects the behavior of charged objects in the vicinity of the field....
. The movement in the filament was heavily magnified and projected through a thin slot onto a moving photographic plate .

The filament was originally made by drawing out a filament of glass from a crucible of molten glass. To produce a sufficiently thin and long filament an arrow

Arrow

An arrow is a pointed projectile that is shot with a bow . It predates recorded history and is common to most cultures....
was fired across the room so that it dragged the filament from the molten glass. The filament so produced was then coated with silver

Silver

Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
to provide the conductive pathway for the current. By tightening or loosening the filament it is possible to very accurately regulate the sensitivity of the galvanometer.

The original machine required water cooling for the powerful electromagnets, required 5 operators and weighed some 600 lb.

Procedure

Patients are sat with both arms and left leg in separate buckets of saline solution. These buckets act as electrodes to conduct the current from the skin's surface to the filament. The three points of electrode contact on these limbs produces what is known as Einthoven's Triangle, a principle still used in modern day ECG recording.