Tips and Tricks for Torsional Orders

Siemens Experimenter Siemens Experimenter
Siemens Experimenter

Taking torsional data with Simcenter Testlab (formerly called LMS Test.Lab)? Here are three tips that will save you time!


TIP 1: Acquisition: Change the channel group from Tacho to Vibration


  1. In Channel Setup, turn on a tachometer channel.
  2. Change the ChannelGroupId from Tacho to Vibration (Figure 1).

With this trick, there is no need to split the tacho channel and route it into both a dynamic channel and a tacho channel. Both a tachometer and vibration channel are calculated.


1.pngFigure 1: Change the ChannelGroupId from Tacho to Vibration in the drop-down menu.

When the tacho channel is set to vibration, it is possible to create order cuts and FFTs from the throughput data.

2.pngFigure 2: Change the ChannelGroupId to vibration and it will be possible to make colormaps and order cuts of the torsional vibration.

TIP 2: Display vibration in angle, RMS, peak, or peak-to-peak


An example of a torsional order is below. The x-axis represents the overall RPM level and the y-axis represents the fluctuation in RPM (torsional vibration).


3.pngFigure 3: 2nd Torsional order from an engine run-up.


To view the torsional vibration in rotational displacement rather than rotational speed:

  1. Right click on the y-axis
  2. Click “Processing”
  3. Click “Integrate (Single)”


4.pngFigure 4: The above menus will open when following the steps to convert the Y-axis to angle.

The graph will then appear as below in Figure 5.


5.pngFigure 5: The Y-axis is now represented in terms of angle.

Want to display the maximum angular displacement?

To change whether the axis is represented in Peak, RMS, or Peak-to-Peak values:

  1. Right click on the y-axis
  2. Click “Processing”
  3. Select “RMS”, “Peak”, or “Peak-to-Peak” from the “Section Scaling” menu

6.pngFigure 6: The above menus will open when following the steps to change the axis scaling.

The graph will then appear as shown below in Figure 7.


7.pngFigure 7: The y-axis is now represented in peak-to-peak format.

TIP 3: Torsional Vibration Animation

Create an operational deflection shape of your torsional vibration:

  1. Create / Import a geometry into Simcenter Testlab using the Geometry worksheet.
  2. Go to the “Torsional node” sub-worksheet of the Geometry worksheet (Figure 8).


8.pngFigure 8: In the Geometry worksheet, open the Torsional node sub-worksheet (red circle near the top).


   3. Click on “Add Disc…”. The “Add disc” window will appear (Figure 9).

      4. Type in the node name, the radius of the rotating component, and the orientation in                      which you want to create the disc.

      5. Click apply and then click close.



9.pngFigure 9: The “Add disc” window allows the user to enter the node name, shaft size, and orientation of the node.

The torsional node will appear in the Geometry Display as shown below (Figure 10).


10.pngFigure 10: The torsional node.

Once all the desired nodes and torsional nodes are created, it is possible to animate the nodes with spectrums, orders, and time histories of the nodes (Figure 11), just as you would animate any geometry.  


(view in My Videos)

Figure 11: An animation of the torsional nodes shows the fluctuation in the shaft as it rotates.


Both translational and rotational vibration can be displayed simultaneously.


Enjoy these tips when working with torsional vibration.


Questions? Email or download the Torsional Vibration White Paper


Rotating machinery dynamics:

Simcenter Testlab Tips: 



I'm trying to animate a torsional acquisition, but I'm not able to do it.


I've acquired two signals from two thooted wheels using a VRS sensor.

Using the Tacho pulse to rpm function I rebuilt the RPM signal of the two wheels, so in the throughput I've the first signal called nPuleggia:1 and the second one called nDamper:1.

Then from the geometry worksheet I created two points with the same name of the RPM signals and then form the torsional node worksheet I created the two discs using the same name of the points previously created.

After this, I put the geometry in a graph and enable the torsional views.

When I drag the signals from the throughput to the discs, they don't animate the geometry.


Can anyone help me?


Thank you

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Matteo,


You can only animate a torsional mode on the Navigator worksheet if an ODS shape has been saved in the past using the Operating Deflection Shape and Time Animation worksheets.  For more information, see


If you bring your throughput data into the Time Animation worksheet, you can animate there and save an ODS shape at any point in time.  That can be viewed in the Navigator.  Or you could process order sections or frequency sections versus time or speed and animate those on Animation and/or Time animation.