Spectrum Analysis
Vibrex 2000 and Vibrex 2000 Plus User Guide 113
These harmonics are mathematically related in frequency to the primary
tone and give the string its tone quality. The following list provides
important facts to keep in mind while working with order analysis:
• A rotor on a helicopter, for example, has a primary frequency, the
RPM, and its harmonics are determined by the number of blades and
multiples of the number of blades. For example, a two-bladed rotor
system turning 300 RPM has a first order (fundamental) of 300 RPM,
a second order at 600 RPM, a fourth order at 1200 RPM, and so on.
• Reciprocating four-cycle engines have harmonics in one-half order
increments, beginning with the one-half order (half the engine speed)
and continuing up through approximately eight times the crank shaft
speed.
• Each engine type has a distinctive spectral signature, and each
different engine of a particular type has a unique signature of its own.
• Engine characteristics that determine spectral signature are the
evenness of combustion, intake losses, ignition timing, internal
component balance, the type of propeller installed, and the condition
of the internal dynamic counterweights (if so equipped).
To view a list of the orders in a signature while using the Vibrex unit,
press the context key next to the <RPM PEAK IPS> line on the screen
display. This action displays the Spectrum Orders screen (see below).
<ORDER @ 500 RPM>
0.5 0.00 IPS
1.0 0.86 IPS
1.5 0.01 IPS
2.0 0.00 IPS
2.5 0.01 IPS
[ANNOTATE ] LIST 1
25SEP96 09:56:46 1A
USE TO ENTER
NOTES TO
ONE’S SELF
DATE, TIME, AND
CHANNEL
NUMBER
LIST OF
VIBRATION
ORDERS
To Next Page
Loading...
Need help?
General
