oscillograph

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A device that records oscillations, as of an electric current and voltage.

Century Dictionary and Cyclopedia

1. n. An instrument for recording alternating-current wave-forms and for the study of electrical oscillations. The oscillograph in its usual form is a development of the D'Arsonval galvanometer in which the moment of inertia of the moving parts is reduced to a minimum and the period of the instrument is sufficiently shortened to enable the moving parts to follow the rapid oscillations that are to be recorded. In 1892 Moler constructed a curve-writing voltmeter for recording the changes in potential in the coils of dynamo-machines which, although lacking in sensitiveness and incapable of giving very rapid fluctuations, must be regarded as the forerunner of the oscillograph. It consistedof a needle of soft iron mounted between the poles of a permanent magnet and carrying a very light pointer of aluminium by means of which the movement of the needle was recorded upon a revolving metallic drum with smoked surface. The frequency was something over 100 complete vibrations per second. In the following year Blondel, to whom the name oscillograph is due, described various forms of the instrument, of which the most successful consisted of a soft iron needle and mirror pivoted between the poles of an electromagnet and vibrating with a frequency of 1,000 oscillations per second. In 1894–95, by greatly reducing the size of the needle and mirror and mounting the same by means of a quartz fiber between the poles of an electromagnet, Hotchkiss succeeded in producing a galvanometer having a frequency of nearly 10,000 single vibrations per second. The essential features of this instrument are shown in Fig. 1 and Fig. 2. The needle is mounted between the pole-pieces N and S, Fig. 1, by means of a fiber stretched between the supports r and r', about which is also wound a coil of wire within which the oscillations to be studied are set up. Rays from an arc-light L₁, Fig. 2, are reflected to the sensitive plate of a camera, S, so constructed that the plate can be shot through the field at right angles to the plane of vibration. With this instrument not only alternating-current curves but likewise curves showing the phenomena of the oscillatory discharge of condensers may be recorded with great fidelity. The form of oscillograph now generally employed is that devised by Duddell in 1897. It consists essentially of a flat strip of phosphor-bronze carried vertically up through the field of an electromagnet, over a roller, and down through the field parallel to itself; to these strips in the middle of the field the mirror and needle are attached. The frequency of oscillation reaches .0003 of a second. When a current is sent through the strip from A to B (Fig. 3) the portion in which the current is flowing upward moves in the opposite direction from that in which the flow is downward, and the mirror is deflected. The spot of light reflected from the mirror is thrown upon the screen for observation, or upon a moving photographic plate for permanent record.
2. n. An apparatus for recording graphically the motions of oscillation of any structure or element as to frequency and magnitude. The element may carry a pen or tracing-point, while a paper, borne on a fixed support, is moved before the tracer as the latter oscillates; or the principle may be reversed: used to record the effect of trains on bridges, or of moving machinery in buildings, or the effect of earth-movements on structures.

Wiktionary

1. n. An instrument for measuring alternating or varying electric current in terms of current and voltage.

GNU Webster's 1913

1. n. a device for making a record of the wave forms of fluctuating .
2. n. (Elec.) An apparatus for recording or indicating alternating-current wave forms or other electrical oscillations, especially of voltages or currents; it usually consists of a galvanometer with strong field, in which the mass of the moving part is very small and frequency of vibration very high.

WordNet 3.0

1. n. a device for making a record of the wave forms of fluctuating voltages or currents