Vibration measurements of tools inside fluids by laser Doppler techniques: uncertainty analysis

In this work a technique based on a laser vibrometer is examined for the vibration measurement of bodies with fluids between the measurement point and vibrometer head. Some mathematical models have been considered and the causes of uncertainty have been correlated with the optical characteristics of the various fluids employed and with their thickness. Optical test benches have been set up and comparative measurements with accelerometers have been carried out in order to verify the mathematical models and estimate other uncertainty sources. Results of the analysis have been used to perform forced vibration measurements on a machine shaft with special care in order to minimize the effect of the noise sources analysed.