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Acquiring Waveforms
3-46
CSA7000 Series, TDS7000 Series, & TDS6000 Series Instruments User Manual
Sin(x)/x interpolation. Sin(x)/x interpolation computes record points using a curve
fit between the actual values acquired. It assumes all the interpolated points fall
along that curve. Sin(x)/x is particularly useful when acquiring more rounded
waveforms such as sine waves. Actually, it is appropriate for general use,
although it may introduce some overshoot or undershoot in signals with fast rise
times, especially if you use zoom and the waveform edges are undersampled.
NOTE. When using either type of interpolation, you may want to set the display
style so that the real samples are displayed intensified and interpolated samples
are dimmed. The instructions under Select the Display Style on page 3--142
explain how to turn on intensified samples.
The instrument can interleave its channels to attain higher digitizing rates
without equivalent time sampling. The instrument applies the digitizing
resources of unused channels (that is, channels that are turned off) to sample
those that are in use (turned on). Table 3--3 lists how interleaving more than one
digitizer to sample a channel extends the maximum digitizing rate.
Once you set horizontal scale to exceed the maximum digitizing rate for the
number of channels in use (see Table 3--3), the instrument will not be able to get
enough samples to create a waveform record. At that point, the instrument will
switch from real to equivalent time sampling to obtain additional samples. (See
Equivalent-Time Sampling on page 3--43.)
T able 3- 3: How i nterleaving affects sample rate
Number of
c
h
a
n
n
e
l
s
i
n
Maximum digitizing rate when real-time sampling
c
h
anne
l
s
i
n
use
CSA7404
CSA7154 TDS7404 TDS7254 TDS7154 TDS7104 TDS7054 TDS6604 TDS6404
One 20 GS/sec 20 GS/sec 20 GS/sec 20 GS/sec 20 GS/sec 10 GS/sec 5 GS/sec 20 GS/sec 20 GS/sec
Two 10 GS/sec 10 GS/sec 10 GS/sec 10 GS/sec 10 GS/sec 5 GS/sec 5 GS/sec 20 GS/sec 20 GS/sec
Three or
Four
5 GS/sec 5 GS/sec 5 GS/sec 5 GS/sec 5 GS/sec 2.5 GS/sec 2.5 GS/sec 10 GS/sec 10 GS/sec
Interleaving