Rockwell Automation 1441-PEN25-Z Enpac 2500 Data Collector - Manual (Page 293)

Rockwell Automation Publication GMSI10-UM002D-EN-E - August 2012 293
FRF Frequency Response Function Extension Module Chapter 11
Num of Lines Sets the number of lines of resolution for the FFT. The Acquisition
time information box changes accordingly.
When set to Automatic, the FRF module automatically chooses the
number of lines after three trial hits. This uses a Uniform window if
possible and automatically increases the lines of resolution to
accommodate the decay time.
If this cannot be achieved, then Force/Exponential is automatically
selected. This function is optimized to work for frequency ranges
between 200 Hz and 4 kHz.
If you select Automatic at a frequency range outside this band, the
algorithm attempts to auto select, but may not achieve good
results. 400 (default)
Windowing Sets the FFT window type to Uniform or Force/Exponential. Force-Exp (default)
Uniform
Num of Averages Sets the number of FFT averages. 5 (default)
Accept/Reject When performing a hammer test, the setting Accept/Reject to
Manual displays a dual time trace and presents the choice to accept
or reject control. Setting it to Automatic, automatically rejects
overloaded data and double impacts. Manual (default)
Automatic
Invert Phase Applies a 180 ° phase offset to the measured data. It is used when
the accelerometer or hammer needs to be inverted at a
measurement position.
Off (default)
On
Save To You can save to the Internal memory or to the storage card. Internal (default)
Card
Good Coherence Enter the threshold at which the FRF plot changes from red (bad
coherence) to green (good coherence). 80% (default)
Table 54 - FRF Analysis Set-up Parameters
Parameter Description Value/Comments