BISOPE series
14- Frequency analysis- Why do frequency analysis?
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A chemical reaction with a certain smell or similar
reflex reaction, an object moving, an object making a sound, and a reaction
with a different color have in common that the human senses can distinguish to
some extent. The reason humans can distinguish causes by these reactions is
that they can be distinguished through certain kinds of sensors (eyes, ears,
mouth, touch, smell). First, the reason for the principle is that there is a
certain pattern. Through this repeating pattern, we can understand and find
some regularity of occurrence in time and space.
Frequency
analysis-finding the rules of repetition.
Frequency refers to the number of repetitions (hertz, Hz)
that occur per second. For reference, RPM is the number of repetitions per
minute, and the time for one repetition is called a period, so the frequency
is also the reciprocal of 'period'.
In the field of vibration and noise, one vibration value
or noise value measured over a wide frequency band is presented as
a representative value, which is called 'Overall' or 'Allpass'.
However, in order to know each frequency component constituting this wideband
signal, frequency analysis is performed. It is because the root
cause can be known only when the member causes are identified.
Frequency analysis uses a ‘filter’,
which is divided into a constant bandwidth or a percentage bandwidth.
The constant ratio bandwidth mainly refers to 'Octave'
whose width increases at the ratio of 2 to the nth power, and is
widely used in noise analysis because humans perceive the senses at a certain
ratio.
On the other hand, a certain
constant bandwidth is used a lot for machine vibration analysis and equipment
diagnosis that require reading a value to find the exact cause, so
the smaller the bandwidth, the more precise. For example, if the measured
values repeated per second are passed through a 1Hz filter, they are
simultaneously displayed as 100 repetitions per second, 3 repetitions, 235
repetitions, etc. can be known at the same time. Again, if the bandwidth is 1
Hz, it means that a frequency filter with an interval of 1 Hz is used.
Therefore, 1Hz, 3Hz, and 235Hz can be distinguished at the same interval and
the amplitudes of their respective frequencies can be compared with each other
under the same conditions. (Of course, 0.1Hz, 0.01Hz, and 10Hz can also be used
as a constant bandwidth filter. )
In summary, frequency analysis,
whether maintenance ratio or constant bandwidth, reads
patterns over time, and since the amplitude of the frequency can be checked, it
is deciphered to find the cause of vibration or noise accurately and
is used as a fundamental data for establishing appropriate countermeasures. It
is used and there is a reason for its use.
All copyright korea CBM written by
BISOPE , vs72@naver.com, 070-4388-0415, www.kCBM.kr
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