Sensitive : (General Electric Review, VOL 42, No. 8.)

✍ Scribed by R.H.O.

• Publisher: Elsevier Science
• Year: 1939
• Tongue: English
• Weight: 59 KB
• Volume: 228
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/s0016-0032(39)90462-x

✦ Synopsis

A device so sensitive that it will indicate the differences in thickness of a fingerprint on a piece of smooth glass, has been developed by J. A. SAMS of the G.E. Works Laboratory at Schenectady. Known as a surface indicator, the instrument is used to determine the smoothness of metal or painted surfaces and indicates minute variations far beyond the range of the human eye. Variations of as little as I/I,OOO,OOO in. are clearly indicated. By its application, the surfaces of bearings or other moving parts of motors and the like that are subject to wear may be tested and their smoothness indicated. The apparatus appears somewhat like a phonograph with its turntable on which is placed the object to be tested, and its sapphire-pointed stylus or needle that passes over the test material as it revolves. Small mechanical impulses are created as the hard point rides over surface irregularities. These impulses are then transmitted to an electromagnetic pickup which converts them into electrical impulses. They are then amplified and transmitted to a recording meter where the surface characteristics are graphically indicated. The stylus or needle is so sensitive that when it is placed on the revolving metal turntable, the invisible vibrations established by a person whistling are shown on the recording meter. R. H. O.