Allen-Bradley 1444-TSCX02-02RB User Manual page 146

Chapter 4 Measurement Definition
Table 30 - FFT (continued)
Parameter Values
FFT Window Type Select from:
• Rectangular
• Flat top
• Hanning
• Hamming
Signal Source Select from:
• Mid-Filter
• Post-Filter
• Alternate Path
Sample Rate
Maximum
Frequency (Fmax)
146
Comment
Select the window function to apply in the FFT signal processing. This table lists the available FFT window types.
Window type Description
Rectangular • No window is applied.
• Also called Normal, Uniform.
• Gives poor peak amplitude accuracy, best peak frequency accuracy.
• When amplitude accuracy and repeatability are important, use Rectangular for transient
signals, or for exactly periodic signals within the time sample (such as integer order
frequencies in synchronously sampled data).
Flat Top • Also called Sinusoidal.
• Gives good peak amplitude accuracy, poor peak frequency accuracy for data with discrete
frequency components.
• Use Flat Top when amplitude accuracy is more important than frequency resolution. In
data with closely spaced peaks, a Flat Top window can smear the peaks together into one
wide peak.
Hanning • A general-purpose window that is similar to a Hamming window.
• Gives fair peak amplitude accuracy, fair peak frequency accuracy.
• Use Hanning on random type data when frequency resolution is more important than
amplitude accuracy. Most often used in predictive maintenance.
Hamming • A general-purpose window that is similar to a Hanning window.
• Gives fair peak amplitude accuracy, fair peak frequency accuracy. It provides better
frequency resolution but decreased amplitude accuracy when compared to the Hanning
window.
• Use Hamming to separate closely spaced frequency components when compared to
Hanning, while providing better peak amplitude accuracy than a Rectangular window
Select the signal source for TWF and the FFT. See the
of signal processing where you can get the processed data.
Signal Source selections for FFTs (FFT Page) and Demand data (Demand Page), for the same channel, cannot be
set to different primary path sources:
• Both can be set to the same source, or...
• One must be set to Alternate Path
Displays the Sample Rate from the Filters properties page for the selected data source.
Displays the maximum Frequency from the Filters properties page for the selected data source.
Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Filters page properties for a description of the various stages