Non contact sensors comparison for dynamic testing of lightweight structures

With dynamic testing, engineers describe different activities focused on the identification of some proper- ties of vibrating structures. The acquisition of the necessary data, requires for the measurements on the component of inputs (excitation) and outputs (responses), commonly applying the necessary sensors directly on the test article. The used load cells and accelerometers, modify the mass and stiffness distributions and subsequently the eigen-properties of the structure. These errors become more evident when testing light weight structures. This paper shows the results of tests performed on a small car turbine with the purpose of identifying the blade mode shapes. The acquisitions were performed using standard accelerometer and two different contact-less systems. One being a particle velocity sensors, the other being a optical displacement transducer. The paper shows how both the contact-less approaches can provide very good results even if the size of the turbine is very small and the blades are extremely light.