Scanning the Past: A History of Electrical Engineering from the Past

Submitted by Dick Reiman, Historian

Copyright 1992 IEEE. Reprinted with permission from the IEEE publication, "Scanning the Past" which covers a reprint of an article appearing in the Proceedings of the IEEE Vol. 80, No. 11 November 1992.

Walter G. Cady and Piezoelectric Resonators

Fifty years ago this month the PROCEEDINGS OF THE IRE (Institute of Radio Engineers) included a paper by Walter G. Cady and Karl S. Van Dyke on proposed standards for describing the piezoelectric properties of quartz crystals. At the time, both were professors at Wesleyan University in Middletown, Connecticut, and Van Dyke was serving as chairman of an IRE committee appointed to recommend standardization of quartz terminology. Cady had devoted much of his career to research on the theory and applications of piezoelectricity and was a leading authority on the subject.

In their paper, Cady and Van Dyke pointed out that there existed a great deal of confusion and inconsistency in the technical literature on quartz resonators, which had led to an "intolerable state." They outlined what they called a "right-left axial system," which they anticipated would, if adopted, serve to remove all "confusion and ambiguity."

Cady was born in Providence, Rhode Island, in 1874 and graduated from Brown University in 1895. After receiving an M.A. from Brown in 1896, he continued his education in Germany, where he earned a Ph.D. at the University of Berlin in 1900. He worked at a magnetic observatory of the U.S. Coast and Geodetic Survey during 1900 and 1902, joining the Wesleyan faculty in 1902, where he taught until 1946.

Prior to World War I, Cady investigated arc discharges and various types of detectors of wireless waves. During the war, he participated in research on submarine detection conducted at a U.S. Navy facility in New London, Connecticut. It was at this time that he began a study of piezoelectricity using Rochelle salt crystals as transducers. He observed unusual effects in crystals operated near resonance, which led him to the conception of radio frequency applications of crystal resonators. He received two fundamental patents on crystal resonators and their applications to radio in 1923. In April 1922 he published an IRE paper on the use of quartz resonators as frequency standards and for maintaining frequency stability of oscillators. In 1923 he undertook an international comparison of frequency standards by comparing a set of his quartz resonators with existing frequency standards in several European countries..

Cady was an active member of the IRE, becoming a fellow of the institute in 1927 and receiving the Morris N. Liebmann Memorial Award in 1928. He served on the editorial board of the PROCEEDINGS and was editor during 1929, thus becoming the only editor other than Alfred N. Goldsmith until 1954. Cady was the president of the IRE during the year 1932.

Cady and Van Dyke presided over an active long-term research program on piezoelectricity at Wesleyan University during the 1920's and 1930's, and a number of graduate theses were produced by their students. (Van Dyke was born in Brooklyn, New York, in 1892 and graduated from Wesleyan in 1916. He earned a Ph.D. at the University of Chicago in 1921 and then taught at Wesleyan from 1921 to 1960.)

During World War II, Cady again worked on military applications of piezoelectricity. He later estimated that around 75 million quartz plates had been fabricated for the U.S. armed forces during the war. Among the applications were supersonic trainers for radar operators, which employed piezoelectric transducers in liquid tanks to generate realistic echoes on radar indicators. Cady received a contract from the Radiation Laboratory at the Massachusetts Institute of Technology for work related to the supersonic trainer.. In 1946 he published a book entitled Piezoelectricity, and he prepared a revised and enlarged edition that was published in 1964. He continued to do consulting work for the Navy and other clients after his retirement from Wesleyan. He also was an enthusiastic amateur ornithologist and kept detailed bird banding records.

Cady died in 1974, having been preceded in death by Van Dyke in 1967.

In addition to its familiar applications in telecommunications and quartz clocks, piezoelectricity is employed in an exotic, recently developed instrument, the scanning tunneling microscope, to maintain nanometer precision.

James E. Brittain

School of History , Technology, and Society

Georgia Institute of Technology