![background image](http://html1.mh-extra.com/html/national-instruments/fd-11601/fd-11601_user-manual_3373502023.webp)
Figure 18. Comparing Typical Magnitude Response of FieldDAQ Filters
Magnitude (dB)
Frequency (Hz/Fs)
0.1
–160
–140
–120
–100
–80
–60
–40
–20
0
20
1
4
Butterworth
Comb
Brickwall
The FieldDAQ filters vary between input delay across signals in the passband:
•
Brickwall
—All input frequencies have the same amount of delay when going through the
filter. Choose this filter for applications where linear phase is required or applications
where data correlation between different devices and configurations is required.
•
Butterworth
—Delays signals by a variable amount depending on their frequency.
•
Comb
—All input frequencies have the same amount of delay when going through the
filter. The comb filter has a shorter delay than the brickwall filter. Choose this filter for
applications where linear phase, short delay, or data correlation of different devices and
configurations is required.
Figure 19. Comparing Typical Input Delay for FieldDAQ Filters
Constant Delay
DC Delay
Maximum AC Delay
Input Dela
y (s)
Frequency (Hz)
0
0
Constant Delay
Butterworth
Comb
Brickwall
Refer to the
FD-11601 Specifications
for details on the amount of variation in the passband
gain and signal delay you can expect for different input frequency ranges.
FD-11601 User Guide
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© National Instruments
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23