30 Chadwick-Helmuth Company, Inc.
Chapter 3 - Getting Started
The Vibrex unit uses a 400-bin FFT setup. If the frequency range selected
is 0 to 24,000 RPM, each bin consists of 60 RPM worth of vibration
energy. As the RPM range goes down, the bins hold fewer RPM, so the
RPM accuracy is generally improved for the spectrum. When the user
prints raw FFT data, both the header information containing the
annotation, channels numbers, RPM range, day/date code, and so on are
recorded with the vibration energy in each bin.
The number in each line of the FFT as printed in the Terminal or
Hyperterminal program is equal to the inches per second (IPS) divided
by 1000. For example, if the range selected was 24,000 RPM, the 9
th
bin
(9
th
numerical entry after the 0, would correspond to 540 RPM in the
spectra and the 200
th
bin (line) would correspond to 12,000 RPM.
The value in storing the vibration measurements as FFT data lies in its PC
versatility. The user can create plots and graphs of the data, using the
Chadwick-Helmuth V2K Plot Software program. For details on how to
use this program to plot FFT data, see the V2K Plot Software User Guide.
3.3.4 Using the PRINT Key
Only data that has been stored to history and the operating Status screen
may be printed. The two methods of finding desired information to be
printed are
• Global printing from the
PRINT key
• Printing with the
REVIEW and PRINT keys
This section explains these printing modes.
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