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Important Oscilloscope Considerations

Important Oscilloscope Considerations

Using Single versus Run/Stop

The oscilloscopes have a Single key and a Run/Stop key. When you press Run (key is illuminated in green), the trigger processing and screen update rate are optimized over the memory depth. Single acquisitions always use the maximum memory available—at least twice as much memory as acquisitions captured in Run mode—and the scope stores at least twice as many samples. At slow sweep speeds, the oscilloscope operates at a higher sample rate when Single is used to capture an acquisition, as opposed to running, due to the increased memory available.

Using Auto trigger mode versus Normal trigger mode

Normal trigger mode requires a trigger to be detected before an acquisition can complete. In many cases, a triggered display in not needed to check signal levels or activity. For these applications, use Auto trigger mode. If you only want to acquire specific events as specified by the trigger settings, use Normal trigger mode. For more detailed discussion of Auto trigger mode and Normal trigger mode, refer to Chapter 3, “Triggering the Oscilloscope.”

Viewing signal detail with acquire mode

Remember how you had to constantly adjust the brightness on old analog scopes to see a desired level of detail in a signal, or to see the signal at all? With the Agilent 54620/40-series oscilloscopes, this is not necessary. The Intensity knob operates much like the brightness knob on your computer screen, so you should set it to a level that makes for comfortable viewing, given the room lighting, and leave it there. Then you can control the detail by selecting an Acquire mode: Normal, Peak Detect, Average, or Realtime as described in the following paragraphs.

Normal acquire mode Normal mode is the acquisition mode that you will probably use for acquiring samples most of the time. It compresses up to 2 million acquisition points per channel for the 54620-series and up to 4 million acquisition points per channel for the 54640-series into a 1,000-pixel column display record.

The 54620-series 200 MSa/s sampling speed specification means that samples are taken every 5 ns. The 54640-series 2 GSa/s sampling speed specification means that samples are taken every 500 ps. At the faster sweep speeds, the running display is built from many individual triggers. If you press the Stop key, and pan and zoom through the waveform by using the Horizontal and Vertical knobs, only the last trigger’s acquisition will be displayed.

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Agilent Technologies 41A, 54621D, 24A, 42A, 54621A, 22A Important Oscilloscope Considerations, Using Single versus Run/Stop