Navigation:  Tutorials > Measurement tutorials > Vibration > DEWESoft 7.0  data acquisition, processing, analyzing and storage software Channel setup

Let's do some vibration measurements in DEWESoft. Since vibration is rather difficult to visualize and, since there were lots of questions about the difference between acceleration, vibration velocity and displacement, it is helpful to actually show the vibration.

This example has a shaker with an attached light plastic structure that has a low natural frequency. At the same time, a video of the movement of this beam was taken with a high speed camera. This helps to really see the vibrations, as they were measured with the accelerometer.

 

It is always advisable to use a card with anti aliasing, such an Orion 1624 for the measurement. Otherwise, we can never be sure that the measuring is correct. Quite often acceleration in  high frequency range (around 20 kHz) is very high. If a card without anti aliasing filters is used, and samples with lower sampler rates are taken, those high frequencies will be mirrored in the lower range. Especially for the measurements like modal analysis this is the most important criteria.

Below is the analog channel setup. There are two DAQP-ACC-A modules for the measurement of vibrations. Let's look how to scale the measurements.

 

 

Sensor setup

There are three ways to perform the setup of the sensor - first, the user can to enter it from the calibration sheet, second, the user can calibrate it with the calibrator, and third the user can use TEDS technology to read out calibration values.

 

First, as usual, we should enter the Units of measurement. In this case we use m/s2 . Then it is the best to go to the Scaling by function section. We check the Sensitivity box and then enter 9.863 mV / m/s2 in the sensitivity field.

Then we need to change the amplifier Range to best fit the current acceleration values and the filter to fit the sampling rate. If the Orion 1624 is used, the filter can be set to the highest values (because the card itself provides sharp anti aliasing filters) unless we intentionally want to have a lower frequency range .

 

 

 

Then we enter in Scaling by two points the acceleration level of 7,07 m/s2 and click calibrate "from RMS" . The current measured voltage level in mV is written to the second point scaling.

 

Then, we can already see if the calibration was successful or not. In the data preview we can see that the peak level is approximately 10 m/s2 and the RMS is around 7,07 . It is advisable to change the CALC TIME option to one second in the data preview to have more stable data. We can also select the Scaling by function and compare measured sensitivity to the calibration data sheet.

 

With a TEDS sensor, it is quite easy to select settings. Plug in the sensors, run DEWESoft and the sensors should be recognized immediately. For MDAQ-ACC, the TEDS, the interface works only if the amplifier is in IEPE mode (it doesn't work in the voltage mode). If this is set up later (after the first scan) or if we plug in the sensor when DEWESoft is already running in the setup screen, the TEDS sensors need to be rescaned. This can be done by clicking on the AMPLIFIER column caption on the basic setup screen and selecting the Rescan modules option.

When a sensor is correctly recognized, scaling factors, sensor serial number and Recalibration date will be read from the sensor. In the setup screen, the user doesn’t we have to enter the sensitivity, since it is already filled in from the sensor. This principle is easy and straightforward, and it prevents user errors.