Tektronix TDS5054, User Manual

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Acquiring Waveforms
TDS5000 Series User Manual
3- 19
Horizontal Scale vs. Record Length vs. Sample Interval vs. Resolution.
These
related parameters specify the horizontal acquisition window. Because the
horizontal acquisition window must fit in the 10 horizontal division display, for
most cases, you can set the Time Duration of the horizontal acquisition window
(10 divs x the scale setting) as described below. By also setting a Record Length
in samples, you indirectly set the Resolution, Sample Interval, and Sample Rate
for the horizontal acquisition window (waveform record). The relationship
between these horizontal elements is:
1.
Time Duration (seconds) = 10 divs (window size) x Horizontal Scale
(sec/div)
2.
Time Duration (seconds) = Sample Interval (seconds/sample) x 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. These
elements behave as follows:
H
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 highest
Sample Rate, the lowest Sample Interval, and the highest Resolution.
H
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
For example, at 200 ps/div and 10 divisions, the record length must be
500 points:
Max Rec Length 500 samples = (10 divs x 200 ps/div)
÷
4 ps/sample
Max Rec Length = 500 samples