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DPO4000 simplified waveform analysis application article


for decades, oscilloscope has been an indispensable tool in research and design, and has stimulated the steady innovation ability of countless industries. One of the main indicators of an oscilloscope is the record length. The recording length is the number of sample points that the oscilloscope can digitize and store in one acquisition. The longer the recording length, the longer the time window that the oscilloscope can capture with high timing resolution (high sampling rate). The first digital oscilloscope in the world can only capture and store 500 points of data, and it is difficult to collect all relevant information around the investigated event. Designers have always been faced with a choice: whether to acquire longer time with low resolution or shorter time with high resolution. What designers really want is to achieve long capture window and high resolution at the same time. With the passage of time and technological development, the speed, simplicity and cost of digitizing more details have become more favorable. But at the same time, the improvement of clock speed, wider and faster parallel design and the shift to serial bus make the bus topology evolve constantly, and the design complexity of the overall system increases sharply. Therefore, designers' demand for high-resolution and longer capture Windows is rising. On the basis of constantly improving national technology centers and post doctoral scientific research workstations, the long speed should be equal to or even greater than the oscilloscope manufacturers' ability to improve the recording length. This development trend will not stop. Moore's law is constantly promoting the development of electronic technology at a faster speed. System design is becoming more complex, and it is correspondingly more difficult to design, build, debug and repair in case of interruption. So what does this mean for modern oscilloscopes? As the design becomes faster and more complex, the demand for long records, more bandwidth and higher sampling rate will also increase. The relationship between these main indicators is not complex. With the increase of bandwidth, the sampling rate must be about five times higher in order to accurately capture the high-frequency components of the signal. When the sampling rate increases, a certain signal acquisition time window requires more samples. For example, capturing a 2-ms 100 MHz signal at 5gs/s requires 10million points of record (2 ms divided by 200 PS sampling interval). Even at lower frequencies, many applications require long records. Capturing a frame of NTSC (two fields at an interval of 1/30 second, with a sampling rate of 100 ms/s to parse all brightness information) requires more than 3 million points (33 ms divided by 10 ns). To capture bus traffic for a few seconds on 1mb/scan bus and diagnose problems in electromechanical system, 10million points may be required to fully analyze. These and various other applications have driven, and will continue to drive, the demand for longer and more detailed data capture Windows

analyze all data

as mentioned earlier, the recording length of the world's first digital oscilloscope is very short. Therefore, it is very easy to view all the items captured by the oscilloscope, because all the contents are displayed on the screen at one time. As records get longer, you need to use horizontal scrolling to view all data. This is not a big problem when moving from one screen information to two screen information, then to four screen information, then to eight screen information, and then to 12 screen information. However, as the recording in each generation of oscilloscope becomes longer and longer, the time required to view all the data captured in one acquisition becomes longer and longer. Now we have to deal with the record length of millions of points, which represents the signal activity of thousands of screens. As an analogy, imagine looking for a needle in a haystack without the help of your favorite search engine, web browser or favorites. Until now, this has been the problem faced by oscilloscope users in long record length oscilloscopes. Obviously, the old solution can no longer work

Figure 1 DPO4000 series wave inspector provides a dedicated front panel control function for effective waveform analysis

Wave inspector

through the DPO4000 series wave inspector control function, processing long records and extracting the required information from waveforms become a simple and efficient process


most digital oscilloscopes on the current market provide some form of zoom function. However, the control functions related to zooming views (zoom factor and position) are often embedded in multiple menus, or coincide with other front panel control functions. For example, the horizontal position of zoom is generally controlled by the horizontal position knob on the front panel. Once the event of interest has been magnified, for example, if you want to move the zoom window to another position in the acquisition, you generally need to rotate the horizontal position knob countless times to slowly move the window to a new position, or zoom in, adjust the window position, and then zoom out. Both methods are inefficient and not intuitive. When you have to browse the menu in order to access these basic zoom control functions, the efficiency will become even worse. Wave inspector provides a dedicated two-layer front panel zoom/pan control function, which can effectively browse waveforms. The internal knob controls the zoom factor. The more clockwise rotating the knob, the larger the magnification. Rotate the knob counterclockwise to zoom out and finally turn off zoom

in Figure 1a, we are detecting an I2C bus. The upper window shows the whole acquisition, and the larger window below is the zoomed part. In this case, we have zoomed in to see the decoded address and data value of two specific packets. The outer ring is a forced/rate sensitive translation control function. Clockwise rotation can translate the amplification window to the right on the waveform, and counterclockwise rotation can translate to the left. The more you rotate, the faster the zoom window moves in the waveform. In Figure 2, by simply rotating the translation control function in the desired direction, we can quickly browse from one group to the next. Even in the acquisition of 10million points, you can quickly move the zoom window from one end of the record to the other end in a few seconds without changing the zoom coefficient

figure 1a The wave inspector provides dedicated front panel zoom and pan control functions

Figure 2 Browse the long acquisition data of I2C bus


when debugging problems, you often don't know what caused the problem, so you're not sure what to look for in the collected waveform. However, you know that you have captured the

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