Walter Guyton Cady (December 10, 1874 – December 9, 1974) was a noted American

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

and

electrical engineer Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

. He was a pioneer in

piezoelectricity Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word ' ...

, and in 1921 developed the first quartz

crystal oscillator A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock ...

. Cady was born in

Providence, Rhode Island Providence is the capital and most populous city of the U.S. state of Rhode Island. One of the oldest cities in New England, it was founded in 1636 by Roger Williams, a Reformed Baptist theologian and religious exile from the Massachusetts ...

, graduated from

Brown University Brown University is a private research university in Providence, Rhode Island. Brown is the seventh-oldest institution of higher education in the United States, founded in 1764 as the College in the English Colony of Rhode Island and Providenc ...

in 1895, and studied 1897-1900 at the

University of Berlin Humboldt-Universität zu Berlin (german: Humboldt-Universität zu Berlin, abbreviated HU Berlin) is a German public research university in the central borough of Mitte in Berlin. It was established by Frederick William III on the initiative ...

, receiving his Ph.D. in Physics in 1900. (From 1895 to 1897 he was also instructor in mathematics at Brown.) He was a Magnetic Observer from 1900 to 1902 with the Coast and Geodetic Survey, and from 1902 to 1946 he was a professor of physics at

Wesleyan University Wesleyan University ( ) is a private liberal arts university in Middletown, Connecticut. Founded in 1831 as a men's college under the auspices of the Methodist Episcopal Church and with the support of prominent residents of Middletown, the col ...

, where his principal interests included electrical discharges in gases, piezoelectricity,

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

, piezoelectric resonators and oscillators, and crystal devices. Before

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

, Cady investigated arc discharges and radio detectors, but during the war became interested in crystals as he worked with

General Electric Company The General Electric Company (GEC) was a major British industrial conglomerate involved in consumer and defence electronics, communications, and engineering. The company was founded in 1886, was Britain's largest private employer with over 250 ...

's Research Laboratory,

Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...

, and the Naval Experimental Station in

New London, Connecticut New London is a seaport city and a port of entry on the northeast coast of the United States, located at the mouth of the Thames River in New London County, Connecticut. It was one of the world's three busiest whaling ports for several decade ...

, on using high-frequency sound generated by piezoelectricity to detect

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s. His early experiments employed Rochelle salt crystals as transducers. After noticing that a quartz crystal connected to a variable-frequency electronic oscillator would vibrate strongly at a very specific frequency, but that at other frequencies it would not vibrate at all, he had the insight to apply crystal oscillators to radio frequency applications. In 1921 Cady designed the first circuit to control frequencies based on quartz crystal resonator, and received two fundamental patents on resonators and their applications to radio in 1923. Cady quickly realized that such circuits could be used as frequency standards, in 1922 published an

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paper on this application, and in 1923 made the first direct international comparison of frequency standards by comparing his quartz resonators with frequency standards in

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, and the

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. Cady was president of the

Institute of Radio Engineers The Institute of Radio Engineers (IRE) was a professional organization which existed from 1912 until December 31, 1962. On January 1, 1963, it merged with the American Institute of Electrical Engineers (AIEE) to form the Institute of Electrical ...

in 1932. During World War II, Cady again worked on military applications of piezoelectricity, including trainers for

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

operators that used piezoelectric transducers in liquid tanks to generate realistic radar returns. He retired to

Pasadena, California Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. ...

, in 1951, where he was a research associate at Caltech. He returned to Providence in 1963. After retirement he consulted for industry and the federal government. Cady held more than 50 patents, and was the inventor of the crystal-controlled oscillator, the highly selective narrow-band

crystal filter A crystal filter allows some frequencies to 'pass' through an electrical circuit while attenuating undesired frequencies. An electronic filter can use quartz crystals as resonator components of a filter circuit. Quartz crystals are piezoelect ...

, one of the principal theorists of the

ferroelectricity Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the a ...

in crystals, and a historian of the science of piezoelectric crystals.Walter G. Cady, ''Piezoelectricity'' (New York and London: McGraw-Hill, 1946). He won the 1928

IEEE Morris N. Liebmann Memorial Award The initially called Morris Liebmann Memorial Prize provided by the Institute of Radio Engineers (IRE), the IEEE Morris N. Liebmann Memorial Award was created in 1919 in honor of Colonel Morris N. Liebmann. It was initially given to awardees who h ...

, and in 1936 was the second American to receive the

Duddell Medal and Prize The Dennis Gabor Medal and Prize (previously the Duddell Medal and Prize until 2008) is a prize awarded biannually by the Institute of Physics for distinguished contributions to the application of physics in an industrial, commercial or busines ...

of the Physical Society of London. He received honorary degrees from Brown University in 1938, and from Wesleyan in 1958. His papers are archived at the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Found ...

and the

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Footnotes

References

* Mason, Warren P., "Professor Walter G. Cady's contributions to piezoelectricity and what followed from them", ''The Journal of the Acoustical Society of America'', Volume 58, Issue 2, August 1975, pages 301-309.
"Walter G. Cady and Piezoelectric Resonators", Proceedings of the IEEE Vol. 80, No. 11 November 1992

Lemelson Center oral history interview

Smithsonian Institution archive entry

IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society memorial proceedings

* Shaul Katzir, "From ultrasonic to frequency standards : Walter Cady’s discovery of the sharp resonance of crystals. " Archive for History of Exact Sciences 62 (5 2008

* Shaul Katzir "War and peacetime research on the road to crystal frequency control. " Technology and culture 51 (1 2010

External links

Oral History interview transcript with Walter Cady on 28 August 1963, American Institute of Physics, Niels Bohr Library & Archives
- Session I
Oral History interview transcript with Walter Cady on 29 August 1963, American Institute of Physics, Niels Bohr Library & Archives
- Session II {{DEFAULTSORT:Cady, Walter Guyton American physicists Wesleyan University faculty 1874 births 1974 deaths Brown University alumni