E2015
Civil/Environmental
- Apr 20, 2015
- 22
I have some strange readings from an impact hammer and acceleromeeters. The hammer is from Piezotronics PCB Model 086D50 and the accelerometers are from Dytran model 3333A and 325M24.
On the first picture called Force you can see the plotted force magnitude in Newtons with number of samples. I have applied in total 4 impact with the hammer and the approx distance between each impact was approx 10 seconds. The force plot like this looks normal.
Figure 1 Force
However, if you zoom in the force plot close to the hammer response at rest, you can see that there are fluctuations in the data. This you can see on the second attached picture named ForceZoomedIn. Red arrows point on the events between impacts. Between each impact there is a distance of approx 10 sec and for this interval the force from the hammer should be around 0. But why do I have these jumps in the reading from x-axis when the hammer is at rest ? Can you clarify why this happens with the data reading from the hammer?
Figure 2 ForceZoomedIn
The same problem occurs with readings from the accelerometers. The attached figures are showing acceleration reading as result of 4 hammer impacts.
On the third picture called Acceleration you can see the plotted acceleration magnitude in m/s^2 with number of samples. The four acceleration peaks are result from four hammer impacts where distance between each impact is approx 10 sec. The acceleration plot like this looks normal.
Figure 3 Acceleration
Again, if you zoom in the acceleration plot close to the acceleration response at rest, you can see that there are drifts in the data over time. Red arrows point on the events between impacts. The fluctuations are present for both accelerometer models. This you can see on the fourth attached picture named AccelerometerZoomedIn.
Figure 4 AccelerometerZoomedIn
Between each event in the acceleration there is a distance of approx 10 sec and for this interval the acceleration reading should be around 0 because there is no excitation of the structure. But why do I have these jumps in the noise reading from x-axis when the vibration dissipates out?
Thank you!
Emina B.
On the first picture called Force you can see the plotted force magnitude in Newtons with number of samples. I have applied in total 4 impact with the hammer and the approx distance between each impact was approx 10 seconds. The force plot like this looks normal.
Figure 1 Force
However, if you zoom in the force plot close to the hammer response at rest, you can see that there are fluctuations in the data. This you can see on the second attached picture named ForceZoomedIn. Red arrows point on the events between impacts. Between each impact there is a distance of approx 10 sec and for this interval the force from the hammer should be around 0. But why do I have these jumps in the reading from x-axis when the hammer is at rest ? Can you clarify why this happens with the data reading from the hammer?
Figure 2 ForceZoomedIn
The same problem occurs with readings from the accelerometers. The attached figures are showing acceleration reading as result of 4 hammer impacts.
On the third picture called Acceleration you can see the plotted acceleration magnitude in m/s^2 with number of samples. The four acceleration peaks are result from four hammer impacts where distance between each impact is approx 10 sec. The acceleration plot like this looks normal.
Figure 3 Acceleration
Again, if you zoom in the acceleration plot close to the acceleration response at rest, you can see that there are drifts in the data over time. Red arrows point on the events between impacts. The fluctuations are present for both accelerometer models. This you can see on the fourth attached picture named AccelerometerZoomedIn.
Figure 4 AccelerometerZoomedIn
Between each event in the acceleration there is a distance of approx 10 sec and for this interval the acceleration reading should be around 0 because there is no excitation of the structure. But why do I have these jumps in the noise reading from x-axis when the vibration dissipates out?
Thank you!
Emina B.
