A New Time Standard

From Horology magazine, November 1939

A New Time Standard

The measurement of time has been a fascinating subject for inventors through past centuries. Any kind of uniform movement may form the basis for a clock.  Water flowing through an orifice, a swinging weight, a vibrating spring, a tuning fork, and a vibrating quartz crystal have all been used for this same purpose.  

Now another method, involving the vibration of a stretched wire or string, has been developed by Henry E. Warren of the Warren Telechron Company located at Ashland, Massachusetts. By means of this very simple device time measurements of comparatively high precision may be made. The new time standard or vibratory clock also serves as a source of alternating current capable of driving with the same precision common electric clocks, of which millions are now in use.

As show on the diagram, there is a fine wire A similar to a violin string, which is maintained under tension by a weight C that is connected to the lower end of the wire by a spring coupling B. Electric driving impulses are imparted to the wire by means of two small coils F and G which are in a vacuum tube circuit. Rigidly attached to the center of the wire is a small permanent magnet marked N-S which can move freely inside the coils. This arrangement constitutes a coupling with the vacuum tube whereby energy is fed back to the wire so as to maintain constant vibration.

By proper proportioning of the parts and the use of suitable materials the rate of vibration of the wire A may be made very constant despite variations in temperature or changes in amplitude of vibration. The minute electrical impulses coming from the vacuum tube, which serve to keep the vibrating wire in motion, are amplified so as to provide sufficient energy to operate synchronous motors like those used in Telechron clocks.  The rate of vibration which determines the electric clock rate may be easily and accurately adjusted by adding or subtracting small weights on top of C. 

For certain purposes, especially the driving of large telescopes, slight variations from uniform time are necessary and this new time standard is then provided with a permanent alnico annular magnet D which constitutes a part of the weight C.  Mounted below this magnet and projecting into its air gap is a fine wire coil E which may carry current in either direction from a graduated potentiometer or rheostat at a distant point.

By adjusting this rheostat an astronomer may with the utmost ease adjust the rate of motion of his telescope so as to follow a heavenly body like a planet or a comet which has an apparent motion slightly faster or slower than a fixed star.

The vibrating wire is supported from a massive hemispherical structure, which is cushioned by springs so as to minimize external vibration. This new instrument is capable of measuring time with an error considerably less than one second a day.