National Instruments FD-11634, Руководство пользователя, Страница: 25 / 55

Step Response of FieldDAQ Filters
The shape of the magnitude and phase responses of a filter impacts how signals look in the
time domain. The step response of a filter is typically used to identify the behavior of a filter in
the time domain.
Three important factors of the filter step response are group delay, rise time, and overshoot/
undershoot. The three filters differ instep response across signals in the transition band:
•
Brickwall —Has the longest group delay. The output signal shows overshoot and
undershoot.
• Butterworth —Has a shorter group delay and the longest rise time. The output signal
shows overshoot.
• Comb —Has the shortest group delay and good rise time. The output signal does not
show overshoot or undershoot.
Figure 18. Comparing Typical Step Response of FieldDAQ Filters
Amplitude
Time
1
0
Butterworth
Comb
Brickwall
Rise Time
Group Delay
Undershoot
Overshoot
Refer to the FD-11634 Specifications for details on the amount of variation in the response
you can expect for different input frequency ranges.
Data Rates
You can use the 13.1072 MHz, 12.8 MHz, 12.288 MHz, and 10.24 MHz timebases to generate
data rates. The FD-11634 supports data rates (
f
s
) between 500 Samples/s and
102.4 kSamples/s. By default, NI-DAQmx automatically chooses the most suitable timebase
for a selected data rate. You can also manually select a timebase through the NI-DAQmx API.
Refer to
Timebases in this guide and the FD-11634 Specifications for information about
choosing the correct timebase for your data rate.
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