Tektronix CSA8000B - Manual (Page 93)

Acquiring Waveforms
CSA8000B & TDS8000B User Manual 3- 19
Horizontal Scale vs. Record Length vs. Sample Interval vs. Resolution. These
parameters all relate to each other and specify the horizontal acquisition window.
Because the horizontal acquisition window must fit in the 10 horizontal division
display, for most cases, you just set the duration of the horizontal acquisition
window (10 divs x the scale setting) as described in (1) below. By also setting a
record length in samples, you indirectly set the resolution/sample interval/sample
rate for the horizontal acquisition window (waveform record). The relationships
between these horizontal elements follow:
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
3. Sample Interval (sec/sample) = Resolution (sec/sample) = 1/Sample Rate
(samples/sec)
In (2) above, note that it is Sample Interval that varies indirectly to accommodate
the window time duration (and its scale setting) and the Record Length setting as
these later two elements can be set by you. These elements behave as follows:
H If Record Length or Time Duration vary, Sample Interval varies to accom-
modate, up to highest sample rate/lowest sample interval/highest resolution.
H If you set faster Horizontal Scale settings, decreasing Time Duration, and the
Sample Interval reaches its lower limit, the horizontal scale becomes limited
to a setting compatible with the record length and the lower limit of the
sample interval.
H If you attempt to set longer Record Lengths and the Sample Interval reaches
it lower limit, Time Duration remains constant and the record length
becomes limited. The equation becomes:
Maximum Record Length = Time Duration
÷ Min Sample Interval
For example, at 1 ps/div and 10 divisions, the record length must be no more
than 1000 points:
Max Rec Length 1000 samples = (10 divs x 1ps/div)
÷ 0.01 ps/sample
Max Rec Length = 1000 samples