Basic oscilloscope functions

Oscilloscopes, Fundamentals

Oscilloscopes (or scopes) test and display voltage signals as waveforms, visual representations of the variation of voltage over time. The signals are plotted on a graph, which shows how the signal changes. The vertical (Y) access represents the voltage measurement and the horizontal (X) axis represents time.


Sampling is the process of converting a portion of an input signal into a number of discrete electrical values for the purpose of storage, processing and display. The magnitude of each sampled point is equal to the amplitude of the input signal at the time the signal is sampled.

The input waveform appears as a series of dots on the oscilloscope display. If the dots are widely spaced and difficult to interpret as a waveform, they can be connected using a process called interpolation, which connects the dots with lines, or vectors.

Chart Showing Oscilloscope Functions of Sampling and Interpolation Sampling and interpolation: sampling is depicted by the dots while interpolation is shown as the black line.


Trigger controls allow you to stabilize and display a repetitive waveform.

Edge triggering is the most common form of triggering. In this mode, the trigger level and slope controls provide the basic trigger point definition. The slope control determines whether the trigger point is on the rising or the falling edge of a signal, and the level control determines where on the edge the trigger point occurs.

When working with complex signals like a series of pulses, pulse-width triggering may be required. With this technique, both the trigger-level setting, and the next falling edge of the signal must occur within a specified time span. Once these two conditions are met, the oscilloscope triggers.

Another technique is single-shot triggering, by which the oscilloscope will display a trace only when the input signal meets the set trigger conditions. Once the trigger conditions are met, the oscilloscope acquires and updates the display, and then freezes the display to hold the trace.

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