OSCILLOSCOPE SELECTION GUIDE
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OSCILLOSCOPES
Tektronix offers oscilloscopes for many different applications and uses. To help you choose the
right scope for your needs, the most common criteria for selecting a scope are listed below,
along with helpful tips for determining your requirements.
FIG 01 /
Typical frequency response curve for a general-purpose oscilloscope
1
Bandwidth
All oscilloscopes have a low-pass frequency response that
rolls off at higher frequencies. Oscilloscope bandwidth is
specied as being the frequency at which a sinusoidal input
signal is attenuated to 70.7% of the signal’s true amplitude
– the -3 dB point. Your oscilloscope must have sufcient
bandwidth to capture all relevant frequency components of
your signal. If you regularly work with digital signals, it may
be easier to consider bandwidth by comparing signal and
oscilloscope rise time specications. Use an oscilloscope
with a rise time specication ve times faster than your
signal rise time to keep error below 2%.
Rule: Bandwidth > 5 x Highest Signal Frequency
3
Sample Rate
The faster an oscilloscope samples, the greater the resolution
and detail of the displayed waveform, and the less likely that
critical information or events will be lost. Tektronix
recommends at least 5X oversampling to ensure signal
details are captured and to avoid aliasing.
Rule: Sample Rate > 5 x (Highest Frequency Component)
4
Record Length
Record length is the number of samples the oscilloscope
can digitize and store in a single acquisition. Since an
oscilloscope can store only a limited number of samples,
the waveform duration – or length of “time” captured – will
be inversely proportional to the oscilloscope’s sample rate.
A longer record length enables a longer time window to be
captured with high resolution.
Rule: Captured Time = (Record Length) / (Sample Rate)
5
Vertical Resolution
The resolution of an oscilloscope's analog-to-digital
converters determines its ability to capture and measure
signal detail. 12-bit converters measures 4096 levels while
8-bit converters measure 256 levels.
6
Features and Analysis Capability
Tektronix oscilloscopes offer a range of features and analysis
capabilities. When choosing your scope, you should review
available triggers, waveform search tools, automated
measurements, and analysis packages such as serial bus
analysis, jitter and power analysis to ensure they meet
your needs.
2
Input Channels
Having more input channels lets you see more of what’s
going on in your design. Today’s oscilloscopes offer more
than just 2 or 4 analog input channels.
• Newer scopes are available with up to 6 or 8 input
channels
• Mixed signal oscilloscopes offer digital channels to
expand visibility beyond the analog channels available on
the instrument
• If you are working with RF signals, the Tektronix MDO
Series of mixed domain oscilloscopes offers a built-in
spectrum analyzer.
100
85
70.7
0.1 0.5
FREQUENCY (GHZ)
AMPLITUDE (%)
1.0
For more information about
oscilloscope specications, download
the XYZs of Oscilloscopes Primer.
Choosing Your Oscilloscope