The ability to effectively troubleshoot designs can be affected by the quality of the oscilloscope’s display. Users may not be able to view critical signal anomalies if they are using an oscilloscope with a low-quality display, while an oscilloscope that shows signal intensity gradations reveal vital waveform details, such as signal anomalies, in a vast variety of digital and analog signal applications.
Generally, engineers perceive DSOs (digital storage oscilloscopes) as two-dimensional device that display the graphical representation of voltage versus time. However, oscilloscopes actually have a third dimension, which is known as the z-axis. At a specific X-Y location, this dimension shows that constant waveform intensity gradation is a function of the signal’s frequency of occurrence. While intensity modulation, or the third dimension, is a natural phenomenon in analog oscilloscopes’ vector-type display, this is missing in digital oscilloscopes due to early limitations in digital display technology.
When searching for signal anomalies, display intensity gradation plays an important role specifically when viewing complex-modulated analog signals like read-write disk head signals, video and digitally controlled motor drive signals. In addition, intensity gradation is of much use also in various mixed-signal applications fitted in embedded microcontroller and microprocessor technologies common in industrial, automotive and consumer markets. Moreover, intensity gradation can also show statistical data about vertical noise, edge jitter as well as the relative occurrence of anomalies even when viewing purely digital waveforms.
When debugging digital circuitry, intensity gradation is very helpful in uncovering signal anomalies. It also helps users view waveforms containing noise, jitter and infrequent events.
In an effort to emulate the display quality of analog oscilloscopes, digital oscilloscope vendors have recently offered z-axis intensity gradation but with varying levels of success.
Complex-modulated signals require an oscilloscope with adequate display quality to allow users to view large pictures and then zoom in to view the small details.
Taking for instance the NSTC or PAL composite video signal, which is a complex-modulated analog signal, capturing one using an analog oscilloscope shows that although its display may flicker, important information are embedded in the displayed waveform envelope. On the other hand, a look at the display of an older digital oscilloscope, which represents some of the entry-level DSOs offered in the market today, reveals that the waveform detail of similar signal is visually lost. Thus, it comes as no surprise that today’s video labs are littered with analog oscilloscopes.
However, several digital oscilloscopes in the market today have finally matched the visual quality offered by analog oscilloscopes. This latest breed of digital oscilloscopes can display repetitive analog signal with the same quality as that of analog oscilloscopes. With the same visual resolution, the oscilloscopes can also capture, display as well as store complex single-shot signals — a capability that analog oscilloscopes fall short of, as it is limited to displaying repetitive signals only.
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