Oscilloscope

Oscilloscopes are used in such fields as industry, medicine, and scientific research. Electronics engineers use the instruments to test computers, radios, and other electronic equipment. Physicians use them to study electrical impulses from the brain or heart. Light, mechanical motion, and sound can be studied with oscilloscopes. Devices called transducers change these forms of energy into electrical signals.

The screen of an oscilloscope is the front of a cathode-ray tube, a special type of vacuum tube. Inside the tube, a device called an electron gun projects a beam of electrons onto the fluorescent screen. Any sideways or up-and-down movement of this beam leaves a glowing line on the screen. A circuit called the time base causes the beam to move repeatedly from left to right. At the same time, the signal to be studied is fed into the oscilloscope and causes the beam to move up and down. This movement corresponds to oscillations (vibrations) in the signal. The beam moves up and down while moving from left to right. As a result, the beam traces a pattern on the screen. This pattern represents the oscillating signal.

A digital oscilloscope can "remember" the signal and so can recall and repeatedly display a brief event, such as the seismic wave of an earthquake. The oscilloscope measures the signal and stores it in a computerlike memory as a sequence of 1's and 0's. The measurements usually can be recalled at a faster or slower rate than they were recorded. For example, a seismic wave that lasted half a minute can be played back in as little as a fraction of a second.

An oscillograph is a type of oscilloscope that can record electrical signals. Certain types of oscillographs change electrical signals into mechanical movements that are recorded on paper or photographic film. For example, some oscillographs use a lightweight pen called a stylus to draw a wavy line on a moving paper chart.

Contributor: Richard W. Henry, Ph.D., Prof. of Physics, Bucknell Univ.

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