精密機械振動測試及分析
VIBRATION FOR PRECISION MACHINERY
…
Nguyen Thien Toan ( M981Y208)
葉銘傑
(M9810210)
精密機械振動測試及分析
VIBRATION FOR PRECISION MACHINERY
Objective: Practice the connection of Vibration measurement system and understand
the parameters stting of FFT analysis, CPB analysisand overall vibration
measurement.
Equipment: Low frequency accelerometer (PCB393B12202), Pre-Amplifier and
Power Unit (PCB482A16), Dynamic Frequency Analyzer (B&K3560 and Pulse),
Cables.
1. FFT spectrum analysis
1.1 Frequency
Objective：do the experiences in different frequency : 400 Lines (1k Hz) 、1600 Lines
(500 Hz)、6400 Lines (100 Hz) )，Compare the difference between them
Comparison : the higher frequency , the higher resolution, but it takes more time to
measure. The result can see in the figure below.
1.2 Overlap
Objective：do experiments with different overlap ratio.
With different overlap ratio we have different period time to measure, the shortest
time measurement was taken with max overlap ratio, the longest time was taken with
0% overlap.
Overlap max setting will overlap 95% of the last calculating stack.
The result be showed in the figure 2.
1.3 Averaging
Objective：change the averaging mode and compare the result
The results can be displayed in the figure 3. The result have just a bit difference
The Peak Averaging mode show the maximum value of the vibration measured. The
Exponential Averaging mode use to monitor the vibration in real time.
2. CPB spectrum analysis
In the CPB spectrum analysis, we will analyze the Filter Setting, Averaging and Hold
the two set of spectral analysis, respectively
2.1 Filter Setting
Objective: In the CPB spectrum analysis, we first compare Filter Setting the impact
on the results from (Figure 4) can be found in the same bandwidth out insurance in 1 /
1 Octave and 1 / 24 Octave analysis of the differences in the same bandwidth in 1 / 24
Octave the more intensive graphics shown, that the interception of data within the
same bandwidth, the more accurate, while we can find 1 / 1 Ovtaver 1 cell is equal to
1 / 3 Octave 3 lattices is equal to 1 / 24 Ovtaver 24 cells, can be seen Filter Setting
parameters for the control of numerical resolution, so when we do vibration analysis,
if we need more detailed results of the small vibration Filter Setting on the need to
adjust for the 1 / 24 Octave, the opposite of if we are to look at the average vibration
may use 1 / 1 Ovtaver or 1 / 3 Ovtaver to display.
2.2 Averaging and Hold
Objective: Understanding the Filter Setting parameter settings.
We will do Averaging and Hold Parameters for comparison, Averaging and Hold is set
to Linear (2s) 2s after the start when the results of analysis after the end of the
Averaging and Hold Set Exponential time FFT with previous spectral measurements
made by the same time, the icon will change to follow changes over time.
2.3 Full analysis of vibration
Objective：we investigate the "Exp", "Lin", "Peak" the three categories, from (Figure
5) can be found in "Exp", "Lin", "Peak" between difference, "Exp" change over time
change on, he "Lin", "Peak" more discovery, "Peak"-60dB maximum.