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Keysight Technologies
Oscilloscope Waveform Update Rate
Determines Probability of
Capturing Elusive Events
Application Note
Introduction
How to Increase Your Odds of Finding Infrequent Glitches
Although often overlooked when evaluating performance of various oscilloscopes for purchase,
waveform update rates can be extremely important--sometimes just as important as the traditional
banner specifications including bandwidth, sample rate, and memory depth. Even though a scope's
waveform update rate may appear fast and lively when viewing repetitively captured waveforms on
your scope's display, "fast" is relative. For example, a few thousand waveforms per second will
certainly appear lively and fast, but statistically speaking this can be very slow if you are attempting to
capture a random and infrequent event that may happen just once in a million occurrences of a signal.
There are three reasons why fast update rates are important for today's oscilloscopes. First, if an
oscilloscope updates waveforms very slowly, it can make using the oscilloscope very frustrating. If you
rotate the timebase control, you expect the oscilloscope to respond immediately--not seconds later
after the scope finishes processing data. Secondly, fast waveform update rates can improve
oscilloscope display quality to show subtle waveform details such as noise and jitter with display
intensity modulation. But most importantly, fast waveform update rates improve the scope's
probability of capturing random and infrequent events that may be keeping you up late at night.
The Keysight Technologies, Inc. InfiniiVision Series oscilloscopes not only provide the fastest waveform
update rates when you use just the scope channels (up to 1,000,000 waveforms per second), but they
also are the only MSOs in the industry that can maintain these fast update rates when you are using
logic acquisition channels and/or serial bus decoding. Although other vendors may specify relatively
fast banner waveform update rate specifications for their MSOs, when you use logic channels and/or
serial bus decoding, these other scopes' update rates drop significantly.
This application note includes side-by-side measurement examples that compare the probabilities of
capturing an anomalous event using various vendors' MSOs. But let's first review some of the factors
that impact oscilloscope update rates, and then we will show you how to compute probabilities of
capturing infrequent events.
03 | Keysight | Oscilloscope Waveform Update Rate Determines Probability of Capturing Elusive Events- Application Note
Understanding Oscilloscope Dead Time
When you debug new designs, waveform and decode update particular setup condition used. The following equation
rates can be critical--especially when you are attempting to summarizes how to compute an oscilloscope's dead-time
find and debug infrequent or intermittent problems. These are percentage:
the toughest kinds of problems to solve. Faster waveform and
decode update rates improve a scope's probability of capturing % DT = Scope's dead-time percentage
elusive events. To understand why this is true, you must first = 100 x [(1/U)