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114 Chapter 4
Making Measurements
Making the Waveform (Time Domain) Measurement
In addition, the following parameters can be modified:
•
Sweep Time - Allows you to specify the measurement acquisition time
which is used as the length of the time capture record. The range is
1.0
µs and 100.0 s, depending upon the resolution bandwidth setting
and the available internal memory size for acquisition points.
•
Res BW - Allows you to set the measurement bandwidth. The range is
10 Hz to 7.5 MHz. A larger bandwidth results in a larger number of
acquisition points and reduces the maximum value allowed for the
sweep time.
•
Advanced - Allows you to access the menu to change the following
parameters. Changes from the default values may result in invalid
data.
—
Pre-ADC BPF - Allows you to toggle the pre-ADC bandpass filter
function between
On or Off. The default setting is Off. The
pre-ADC bandpass filter is useful for rejecting nearby signals, so
that sensitivity within the span range can be improved by
increasing the ADC range gain.
—
RBW Filter - Allows you toggle the resolution bandwidth filter
selection between
Flat and Gaussian. If set to Gaussian, the filter
provides more even time-domain response, particularly for
“bursts”. If set to
Flat, the filter provides a flatter bandwidth but is
less accurate for “pulse responses”. A flat top filter also requires
less memory and allows longer data acquisition times. For most
waveform applications, the Gaussian filter is recommended.
—
ADC Range - Allows you to access the menu to select one of the
ADC ranging functions:
❏
Auto - Select this to cause the instrument to automatically
adjust the signal range for optimal measurement results.
❏
AutoPeak - Select this to cause the instrument to continuously
seek the highest peak signal.
❏
AutoPeakLock - Select this to cause the instrument to adjust the
range for the highest peak signal it identifies, and retains the
range settings determined by that peak signal, even when the
peak signal is no longer present.
❏
Manual - Allows you to access the selection menu: −6 dB, 0 dB, +6
dB
, +12 dB, +18 dB, +24 dB, to set the ADC range level. Also note
that manual ranging is best for CW signals.
— Data Packing - Allows you to select Auto (the default) or the Short (16
bit)
, Medium (24 bit) and Long (32 bit) methods of data packing. The
short, medium, and long methods are not compatible with all
settings and should not be used unless you are familiar with data
packing methods.
Auto is the preferred choice.