Abstracts of Technical Articles by Bell System Authors (01 July 1945)

A.S.T.M. Bulletin, M a y 1945. Quarterly Applied Mathematics, July Electronic Industries, August 1945. 1945. 462 ABSTRACTS OF TECHNICAL ARTICLES 463 heated type, are used in simple feedback amplifiers as regulation and control devices to effect the economies inherent in an entirely electrical system by eliminating such mechanical devices as motor-driven condensers, sliding contacts and rotary switches. Dynamic Measurements on Electromagnetic Devices.4 E. L. NORTON. 

A method is presented by which measurements of flux may be made at any desired time during the operate cycle of an electromagnet. Apparatus is described which operates the magnet cyclically at an accurately held rate, and provides a means for measuring flux either by the use of a search coil or by the operating winding of the magnet itself. When using a search coil, it is connected to a direct-current milliammeter at the time in the cycle at which the value of the flux is desired and disconnected at the end of the cycle or just before the magnet is energized for the next pulse. 

If proper precautions are taken, the steady reading of the instrument is an accurate measure of the difference in the flux in the coil between the time it is connected to the meter and the time it is removed, or, since the latter is zero except for residual flux, the reading is a direct measure of flux. The same apparatus may be used for the measurement of instantaneous current by the addition of an air core mutual inductance, and its use is extended to the measurement of armature position and velocity by the addition of a photoelectric cell and the proper amplifiers.