Oscilloscope Reference Independent versus shared window
The relationship between thes e horizontal elements is as follows:
Time Duration (seconds) = 10 divs (window size) × Horizontal Scale (sec/div)
Time Duration (seconds) = Sample Interval (seconds/sample) × Record Length (samples), where Time
Duration is the horizontal acquisition window time duration, and Sample Interval (sec/sample) =
Resolution (sec/sample) = 1/Sample Rate (samples/sec)
Note that it is the Sample Interval that changes to accommodate the window Time Duration (and its scale
setting) and the Record Length setting.
Theelementsbehaveasfollows:
If the Record Length or Time Duration change, the Sample Interval will vary to accommodate the
change. The Sample Interval can vary up to the highe st Sample Rate, (this corresponds to the lowest
Sample Interval, and the highest Resolution).
If the Sample Interval reaches its lower limit, the Record Length must decrease if the Time Duration
decreases (you set faster scale settings), or Time Duration must increase (forcing slower scale settings)
if Record Length increases (you set longer record lengths. The equation becomes: Maximum Record
Length
= Time Duration ÷ Min Sample Interval.
NOTE. Resolution and the equivalent elements, Sample Interval and Sample Rate, are derived and cannot
be set directly. You can, however, check the Resolution at anytime in the resolution readout. Also note that
the front-panel Resolution knob actually adjusts the Record Length to increase sample density.
This discussion assumes that Horizontal Scale is held constant. You can hold the Sample Rate constant
instead by clicking Hold Sample Rate constant on the Record Length tab of the User Preferences control
window.
What do you want to do next?
Overview Learn about horizontal scale. (see page 833)
Learn about record length. (see page 900)
L
earn about horizontal resolution.
(see page 193)
Independent versus shared window
The instrument applies the same horizontal acquisition window to all channels from which it acquires
data. Unlike the vertical acquisition window that you size and offset independently for each channel, the
same time/div, resolution (record length), and horizontal position (from the same trigger point) apply to
all channels simultaneously.
One trigger, from a single trigger source, will locate a common horizontal acquisition window for all active
channels, which you can shift in parallel by setting the horizontal position control.
DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series 685
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