Rotation angle and Torsional vibration

Hello,

I am carrying out vibration tests on internal combustion reciprocating engine. In particular, thanks to two sensors with missing teeth (60-2) I evaluate both the angular displacement at both ends of the crankshaft and the torsion angle. However, if I do the difference between the angular displacements, I do not get the torsion angle as I would expect (see image). So I wonder what is the connection between these three channels of the TV module (Rotation angle 1, Rotation angle 2 and Torsion angle).

Dear Valerio,
thank you for contacting us. From our Rotational and Torsional Vibration Manual the Rotational angle is filtered angle value of vibration. The Torsional angle is dynamic torsional angle that is the angle difference from sensor 1 to sensor 2. The difference of the rotational angles does not equal the difference of angles from the two sensors.

Kind regards.