An experienced video design engineer can quickly determine the quality of analog signal generation from this display.įigure 2 shows an older digital oscilloscope display without z-axis intensity modulation. Even though the display “flickers” when you view this waveform at 5 ms/div, there is important information embedded within the displayed waveform envelope. Figure 1 shows one frame of composite video photographically captured from an analog oscilloscope's display. ![]() Many engineers are familiar with standard NTSC or PAL composite video signals, which are complex-modulated analog signals. If you are working with complex-modulated signals, you need a scope with sufficient display quality to let you look at the big picture and then zoom in to see the details. Recently, all major digital oscilloscope vendors have begun to provide z-axis intensity gradation – with varying degrees of success – in order to emulate the display quality of an analog oscilloscope.Ĭomplex-modulated analog signal applications But even when you are viewing purely digital waveforms, intensity gradation can show statistical information about edge jitter, vertical noise, and the relative occurrence of anomalies. Intensity gradation is also helpful in a wide variety of mixed-signal applications found in embedded microprocessor and microcontroller technologies common in the automotive, industrial, and consumer markets. Now, it is making a comeback.ĭisplay intensity gradation can be extremely important when you are looking for signal anomalies, especially when you are viewing complex-modulated analog signals such as video, read-write disk head signals, and digitally controlled motor drive signals. Due to early limitations of digital display technology, this third dimension, intensity modulation, was missing when digital oscilloscopes began replacing their analog counterparts. In analog oscilloscope technology, intensity modulation is a natural phenomenon of the scope’s vector-type display, which is swept with an electron beam. This third dimension shows continuous waveform intensity gradation as a function of the frequency of occurrence of signals at particular X-Y locations. But there is actually a third dimension to a scope: the z-axis. ![]() The third dimension: intensity modulationĮngineers traditionally think of digital storage oscilloscopes (DSOs) as two-dimensional instruments that graphically display only voltage versus time. We also discuss a methodology for quantifying display quality to make it easier to compare scope displays objectively. In some examples, we also show the results displayed on a traditional analog oscilloscope. This application note compares display quality for a variety of analog and digital signals using Agilent’s 6000 Series mixed signal oscilloscope (MSO) and LeCroy’s WaveSurfer 400 Series scope. A scope that is capable of showing signal intensity gradations can reveal important waveform details, including signal anomalies, in a wide variety of both analog and digital signal applications. If your oscilloscope has a low-quality display, you may not be able to see critical signal anomalies. The quality of your oscilloscope’s display can make a big difference in your ability to troubleshoot your designs effectively.
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