Evaluating Oscilloscopes for Best Signal Visibility
Mixed signal oscilloscopes (MSOs) have become the tool-of-choice for many of today's designers of embedded devices. MSOs add sixteen or more logic analyzer acquisition channels—along with serial bus triggering and protocol decoding—to basic scope functionality, making it possible for R&D engineers and technicians to debug their mixed-signal designs faster. Although basic acquisition performance, such as bandwidth and sample rate, may not be degraded in today's MSOs relative to their DSO counterparts, there is one very important performance characteristic that is compromised in all vendors' MSOs—except Agilent's. And that is waveform and serial bus decode update rates.
This application note includes side-by-side measurement examples that compare the probabilities of capturing an anomalous event using various vendors' MSOs. First, however, the paper reviews some of the factors that impact oscilloscope update rates, and then shows how to compute probabilities of capturing infrequent events.