Duddell oscillograph

Duddell oscillograph

[dü′del ä′sil·ə‚graf]
(electromagnetism)
A moving-coil oscillograph; the current to be observed passes through a coil in a magnetic field and a mirror attached to the coil reveals its movement.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.