Sir Charles Wheatstone

by Mary Ann Hoffman

Through the generosity of IEEE Life Fellow Les Balter, the IEEE History Center recently acquired a very handsome Wheatstone Bridge. In researching the Bridge, we discovered some interesting information on Wheatstone, hence, this article.

According to Wikipedia... A Wheatstone bridge is an instrument used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer, except that in potentiometer circuits the meter used is a sensitive galvanometer.

Sir Charles Wheatstone was born on 2 February 1802 in the village of Barnwood in the United Kingdom. He was the second son of William Wheatstone, a manufacturer of musical instruments, and was educated in various schools throughout London. During his youth, he saved money to purchase all types of books, including fairy tales, history and science. Wheatstone excelled in mathematics and physics, and learned French, Latin and Greek.

When he was 14 years old, Wheatstone apprenticed with his uncle and namesake, also a maker and seller of musical instruments. Wheatstone took over his uncle’s business at the age of 21. A prolific inventor, he also experimented with acoustics, optics, electricity and the telegraph. Wheatstone invented two new musical instruments, the Wheatstone Baritone English Concertina and the portable harmonium. The harmonium earned him a medal at the Great Exhibition in 1851.

But the invention that would forever be linked to Wheatstone is the Wheatstone Bridge. He publicly admitted that he did not invent it, but he did more than anyone else to invent uses for it, when he "found" the description of the device in 1843. Samuel Hunter Christie (1784-1865) published the first description of the bridge in 1833 in the Philosophical Transactions. Wheatstone had been fascinated with electrical measurements, and worked on many devices for a number of years.

Christie had a different objective for designing the Bridge — to compare electromagnetic forces induced by magneto-electric induction in different metals. Wheatstone showed how it could be used to compare resistances, and he put the necessary circuit into a board with terminals, thus producing the instrument we know today.

After the bridge, Wheatstone’s most famous invention was one of the first practical telegraphs, which he developed along with William F. Cooke. Both gentlemen had been experimenting with telegraphs independently. After seeking Michael Faraday's advice, Cooke was directed to Wheatstone, and in March 1837, Wheatstone and Cooke formed a partnership. They collaborated on the telegraph for several months and applied for an English patent. They were granted six months to come up with the telegraph specifications, which they filed in December 1837. The patent was granted. Later, though, Wheatstone decided that he was not given enough credit for the invention, and a great dispute arose. In the long run, the Morse telegraph came to dominate the field anyway.

Wheatstone was appointed Chair of Experimental Philosophy at Kings’ College, London in 1834. A very shy person, Wheatstone did not enjoy public speaking. He only lectured for one semester, then set out to do pure research for the remainder of his tenure at the College. Because of his shyness, his good friend Michael Faraday gave most of his lectures for him at the Royal Institution. Wheatstone married late in life, at the age of 45, and he and his wife, Emma, raised five children. His nephew, Oliver Heaviside (1850-1925), also a pioneering electrical scientist, saw him as a mentor. Wheatstone encouraged Heaviside to study languages, for the same reason he did — to be able to read other’s papers.

In 1902, Heaviside predicted that there was a conducting layer in the atmosphere that allowed radio waves to follow the Earth's curvature. This layer in the atmosphere, the Heaviside Layer, is named after him. In 1923, the layer's existence was proven when radio pulses were transmitted vertically upward and the returning pulses from the reflecting layer were received.

Wheatstone was knighted in 1868 for his “great scientific attainments and of his valuable inventions.” He received many other honors and degrees, in recognition of his work in myriad fields. He never really retired, working until a few days before his death on 19 October 1875, while attending meetings at the Academy of Science in Paris.

Reference

Brian Bowers, Sir Charles Wheatstone FRS 1802-1875, IEE History of Technology Series, 2001.

 

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