Oscilloscope R eference Reference point
Automatic and Constant Sample Rate mode s are identical, with the exception that in Constant Sample Rate
mode the user cannot set the record length limit. In both cases, the instrument m aintains the sample rate
constant as se
t specified by the user.
NOTE. Manual mode uses the maximum record length available for the instrument you purchased.
What do you w
ant to do next?
Learn more about the Horizontal Setup controls. (see page 842)
Reference point
Use the Ref Point control to define the horizontal r eference point within the acquired waveform. The
horizontal reference point determines the location within the acquired data where the scale controls
will exp
and or contract the waveform.
When Horizontal Delay is On, the reference point is the trigger point plus the Horizontal Delay time.
When the horizontal d elay is Off, the r eference point is the trigger point.
Resolution bandwidth
The resolution bandwidth controls the bandwidth of the spectral analyzer filters. You can adjust the
resolution bandwidth in units of hertz. The resolution bandwidth is measured at the –3 dB points o n
each side of the peak spectral lobe of the filter.
Resolution bandwidth is inversely proportional to the gate duration in the time domain. Changing the
gate duration changes the resolution bandwidth. Changing the spectral analyzer window function also
ch
anges the resolution b andwidth but will not affect the gate duration.
To decrease the resolution bandwidth beyond the present limits, increase the time domain gate duration. If
th
is is insufficient, increase the record length and then increase the gate duration again. You can also try the
rectangular or Hamming window to maximize the frequency resolution (minimize resolution bandwidth).
DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series 903
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