Table 8. Comparing FieldDAQ Filters
Attribute
Brickwall (Default)
Butterworth
Comb
Passband
Tracks sample rate
Configurable independent
of sample rate
Tracks sample rate
Alias Protection
Best—Full
protection
Better—Configurable
protection level
Good—Partial
protection
Latency
High
Medium to high
(configuration-dependent)
Low
Input Delay
Variation versus
Frequency
Constant input delay Variable input delay
Constant input delay
Flatness
Best
Best
Good
Step Response
(Time Domain)
Most delay, ringing
(overshoot/
undershoot)
Mid-level delay,
overshoot
Short delay, no
overshoot/undershoot
Typical
Applications
Analyzing dynamic
properties of signals
Analyzing spectrum
of signals
Filtering out specific noise
sources
Analyzing signals in the
time domain
Reducing measurement
noise
Filtering out specific
noise sources
Analyzing signals in
the time domain
Control applications
Refer to the
FD-11634 Specifications
for details on the amount of variation in the response
you can expect for different input frequency ranges.
Frequency Response of FieldDAQ Filters
The FieldDAQ device uses a combination of analog and digital filtering to provide an accurate
representation of in-band signals and reject out-of-band signals. The filters discriminate
between signals based on the frequency range, or bandwidth, of the signal. How the filter
discriminates signals based on their frequency is known as frequency response. In general, the
frequency response of a filter is described by a signal attenuation (magnitude response) and an
input delay (phase response) for every input frequency.
•
Magnitude Response
—The three important frequency ranges, or bandwidths, to
consider for magnitude response are passband, transition band, and stopband:
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FD-11634 User Guide