NI 9225 Operating Instructions and Specifications
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© National Instruments
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15
Stopband
The filter significantly attenuates all signals above the stopband
frequency. The primary goal of the filter is to prevent aliasing.
Therefore, the stopband frequency scales precisely with the data
rate. The stopband rejection is the minimum amount of attenuation
applied by the filter to all signals with frequencies within the
stopband.
Alias-Free Bandwidth
Any signal that appears in the alias-free bandwidth of the NI 9225
is not an aliased artifact of signals at a higher frequency. The
alias-free bandwidth is defined by the ability of the filter to reject
frequencies above the stopband frequency and equals the data rate
minus the stopband frequency.
Understanding NI 9225 Data Rates
The frequency of a master timebase (
f
M
) controls the data rate (
f
s
)
of the NI 9225. The NI 9225 includes an internal master timebase
with a frequency of 12.8 MHz, but the module also can accept an
external master timebase or export its own master timebase. To
synchronize the data rate of an NI 9225 with other modules that use
master timebases to control sampling, all of the modules must
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