3 Spectrum Analyzer Mode
3.2 Swept SA Measurement
Sweep Time
Controls the time the instrument takes to sweep the current frequency span when
"Sweep Type" on page 491 is SWEpt, displays the sweep time in swept
measurements, and displays the equivalent sweep time when Sweep Type is FFT.
NOTE
In instruments without sweeping hardware, such as some modular instruments,
this control may be labelled “Acquisition Time”
When Sweep Time is Auto, the instrument computes a time that will give accurate
measurements based on other settings of the instrument, such as RBW and VBW.
You can choose a shorter sweep time to improve the measurement throughput (with
some potential unspecified accuracy reduction), but the Meas Uncal indicator will
come on if the sweep time you set is less than the calculated Auto Sweep time. You
can also select a longer sweep time, which can be useful (for example) for obtaining
accurate insertion loss measurements on very narrowband filters. The number of
measurement points can also be reduced to speed the measurement (at the
expense of frequency resolution).
You might need to specify a specific sweep speed to accommodate a specific
condition in your transmitter. For example, you may have a burst signal and need to
measure an exact portion of the burst.
When in Zero Span, there is no “Auto Sweep Time”, so the Auto/Man toggle on this
control disappears.
When Sweep Type is FFT, you cannot control the sweep time, it is simply reported
by the instrument to give you an idea of how long the measurement is taking. The
Auto/Man toggle therefore disappears when in an FFT sweep. In this case the
Sweep Time function is grayed-out.
NOTE
In VXT Models M9410A/11A/15A, Sweep Type is
always
set to FFT, as these
models do not have sweeping hardware. Therefore, in VXT Models
M9410A/11A/15A, the Sweep Time control is
always
grayed-out unless you are
in Zero Span. The value reported on the control is the approximate time that will
be taken to acquire the trace data for one measurement cycle. This is basically
the acquisition time for each frequency segment (“chunk”) multiplied by the
number of segments. The “chunk” time is determined by other parameters, such
as RBW and VBW. The value displayed represents, as close as can be
estimated, the time to “take one sweep”.
When the control is grayed-out, sending the Sweep Time SCPI command
generates an error.
480 Spectrum Analyzer Mode User's &Programmer's Reference
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