Chapter 2 71
Instrument Functions: A - L
BW/Avg
Instrument Functions: A - L
2.3.2 Video BW
Enables you to change the analyzer post-detection filter from 1 Hz to 8 MHz in
approximately 10% steps. In addition, a wide-open video filter bandwidth (VBW) may be
chosen by selecting 50 MHz.
Video BW (Auto) selects automatic coupling of the Video BW
filter to the resolution bandwidth filter using the VBW/RBW ratio set by the
VBW/RBW key.
NOTE Sweep Time is coupled to Video Bandwidth (VBW). As the VBW is changed,
the sweep time (when set to
Auto) is changed to maintain amplitude
calibration. This occurs because of common hardware between the two
circuits, even though the Video BW filter is not actually “in-circuit” when the
detector is set to Average. Because the purpose of the average detector and
the VBW filter are the same, either can be used to reduce the variance of the
result.
Although the VBW filter is not “in-circuit” when using the average detector,
the Video BW key can have an effect on (
Auto) sweep time, and is not
disabled. In this case, reducing the VBW setting increases the sweep time,
which increases the averaging time, producing a lower-variance trace.
However, when the EMI Average detector is selected, the Video BW is
restricted to 1 Hz while the sweep time is set to
Auto.
When using the average detector with either
Sweep Time set to Man, or in zero
span, the VBW setting has no effect and is disabled (grayed out).
A “#” mark appears next to VBW on the bottom of the analyzer display when it is not
coupled. To couple the video bandwidth, press
Video BW (Auto) (or press Auto All).
Key Path:
BW/Avg
Saved State: Saved in Instrument State
Factory Preset: Auto (3 MHz)
Range: 1 Hz to 50 MHz
Remote Command:
[:SENSe]:BANDwidth|BWIDth:VIDeo <freq>
[:SENSe]:BANDwidth|BWIDth:VIDeo?
[:SENSe]:BANDwidth|BWIDth:VIDeo:AUTO OFF|ON|0|1
[:SENSe]:BANDwidth|BWIDth:VIDeo:AUTO?
Example: BAND:VID 1 kHz
BAND:VID?
BWID:VID:AUTO ON
BWID:VID:AUTO?
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