ACES SYSTEMS Cobra II, Руководство пользователя

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Gen II
User Manual
14-5 – Vibration Spectrum Survey Chapter 14 Revision 4.10, Apr 2020
14.1.1.1.5. Use the [

] key to move to the “ Res. Lines: ” field. Resolution is the number of lines of
resolution for the spectra display. Press the [

] key to increase the number of lines up to
3200. Normally 400 to 800 lines are sufficient for spectra. Higher resolutions may be
used when separation of two frequencies of very close proximity is required.
14.1.1.1.6. The “ RPM/Line (Hz/Line) ” field is an informational entry. The frequency unit displayed
is determined by the entry in paragraph 14.1.1.1.2. It will tell you the approximate
interval between one line of resolution and the next. This is based on the minimum and
maximum frequencies selected in paragraphs 14.1.1.1.3 through 14.1.1.1.4 and the Res.
Lines entry selected in paragraph 14.1.1.1.5. This can be helpful if you are trying to
separate one single peak into two very close peaks. The value displayed will be the
frequency interval between each pair of lines on the final spectral display.
14.1.1.1.7. Use the [

] key to move to the “ Average Type ” field. Select the “Average Type” by
scrolling between the available choices using the [

] key. The three available options
are “Normal”, “Expon.” (exponential) and “Peak Hold”. “Normal” averaging displays a
running average of the last specified number of blocks of data. All blocks are weighed
equally in normal averaging. “Peak Hold” averaging plots the highest or worst-case
amplitude for all frequencies and holds that value on the display until a higher value is
acquired. The displayed amplitude will not decrease thus the term “peak hold.” A peak
hold survey will continue to collect data until you stop acquisition by pressing the [OK]
key. “Expon” will show the changes in amplitude as they occur allowing you to view the
data in real time. The analyzer collects data until you stop the data collection by pressing
the [OK] key. Consult your aircraft’s equipment maintenance manual for specific
requirements of a vibration survey or for analysis guidelines.
14.1.1.1.8. Use the [

] key to move to the “ Blocks ” field. Using the keypad, enter the number of
data blocks you wish to be used in the calculations. The default value is 4. The valid
range is 0 to 999. Remember that a higher number of blocks, while providing more
reliable data, also require more time to acquire and memory to store. The default value of
4 is sufficient for most applications. This means that four blocks of data will be acquired
before the averaging process is executed. The analyzer then acquires four more blocks
and the process repeats until data acquisition is terminated.
NOTE
Sensor Channels C & D are only available on the Viper II
14.1.1.1.9. Use the [

] key to move to the “ Units ” column of the “Channel A:” row. Select an
engineering unit from the available list by using [

] key. A selection of “None” in the
field indicates there will be no input to the Channel adjacent to the field where the word
“None” appears. Your selection determines the engineering units in which the vibration
spectra will be displayed. Each channel is independent of the others so that the type of
unit can vary between channels. For example, you may select “IPS” in channel A for
velocity and “g’s” in channel B for acceleration. Any selection, other than “None” will