Scopes shorten time to insight.(OSCILLOSCOPES)

What is a scope? This is a difficult question to answer because the definition of an oscilloscope continues to change. To a purist, the only real oscilloscope is one that displays a waveform in direct response to the input signal: in other words, an analog cathode-ray oscilloscope with electrostatic vertical deflection plates driven by an amplified version of the input.

In contrast, all digital storage oscilloscopes (DSOs) manipulate a digitized version of the analog input in various ways before producing the displayed waveform. Some combined analog/digital scopes retain an electrostatic CRT but can store a waveform digitally and display that data via a DAC. However, most DSOs today use a magnetically deflected raster-scan CRT or a flat-panel LCD as the visual display device, and these are driven digitally.

As DSOs developed, memories became longer, more channels were added, bandwidths increased, and disk storage was provided so captured waveforms could be archived. Mathematical operations could be performed on data allowing rise time and pulse width measurements and comparison between live and reference waveforms. And new data could be created such as an instantaneous power waveform produced by multiplying acquired voltage and current waveforms.

When PCs became sufficiently fast and their displays good enough, data acquisition boards were coupled with scope application software to make PC-based scopes. Certainly, such a system displays waveforms much like a conventional scope does, and it is easier to manipulate files within the PC rather than have them stored in a stand-alone scope. But, exactly what makes an oscilloscope different from a data acquisition system?

Distinguishing Characteristics

Visual Capabilities

Typically, scopes deal with much faster signals than most data acquisition systems can handle, and scope applications require waveform display. The emphasis on a displayed waveform differentiates a scope from other instruments. Many writers have commented that an oscilloscope acts as an electronic engineer's eyes, and this remains true regardless of how the displayed image is formed.

How can you tell a scope from a data acquisition instrument? The short answer is that many times you can't. A scope might be used for high-speed data acquisition with no one observing the displayed images. And, software is sufficiently refined today that signals captured by a data acquisition system can be made to look just like waveforms from a scope. As the CEO of one PC-based scope company commented, the distinctions among data acquisition, digitizer, and scope products are becoming blurred.

High Bandwidth and Sample Rate

If you are looking at single-shot events spaced far apart in time, there's little difference in the results these instruments might produce. However, one factor becomes apparent if the events occur close together. A scope tends to have a short re-arm time, which means that almost immediately after one waveform has been displayed you can capture and display another. Many digitizers also have short re-arm times, but accompanying software may not emphasize display responsiveness.

This capability is important because the way a waveform changes in time can convey as much information as the signal's basic shape. …

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