How to read an oscilloscope

Written by mike smith | 13/05/2017
How to read an oscilloscope
Oscilloscppes produce "pictures" of sound waves. (waveform 20 image by chrisharvey from

An oscilloscope is a device that represents a sound as a wave on a screen. The device compares the voltage of the signal, then plots it against time. This effectively gives a visual representation of the way a soundwave looks as it moves through the air. Oscilloscopes are often used to test audio circuits and to compare sounds. By comparing the waves various sounds create, you can begin to understand what differences in the wave will sound like and eventually how different waves interacting will sound. It helps to have a basic idea of what each part of the wave means.

While sending the signal you would like to examine, adjust your oscilloscope's amplitude setting until you can see both the top and bottom of each wave. The scale along the side of the screen should adjust accordingly.

Examine the waves that the oscilloscope displays on its screen. The distance from the bottom of one of the waves, called the trough, to the top, or crest, is called the amplitude. The greater the amplitude, or distance between trough and crest, the louder the sound that the oscilloscope received. Compare the amplitude of the recorded wave to the scale on the side of the screen to get an approximate idea of the sound's volume.

Check your oscilloscope's time adjuster to get an idea of how much time the distance across the screen will represent. The shorter the amount of time, the more precise the measurement can be, but you will be able to view less of the entire signal.

Compare the number of times that the wave alternates from crest to trough and back to the scale along the bottom of the screen. This measurement is called the frequency. The more often a wave oscillates in a given time, the higher the frequency. Frequency is measured in Hertz. A sound that cycles once per second is one hertz. Count the number of cycles that your wave completes in the unit of time along the bottom axis of the oscilloscope's screen. You can find the frequency of your sound in Hertz by multiplying the cycles by whatever fraction of a second they were completed in. For example, if you counted the number of cycles completed in a 10th of a second, multiply by 10 to find Hertz.

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