Acoustic-Based Liquid Level Determination in Process Vessels using PVDF Sensors

The paper describes the interrogation of process vessels using acoustic signals that are generated using non-invasive mechanical impact that is generated using a solenoid driven actuator. The signals are detected using piezoelectric polyvinylidene fluoride (PVDF) sensors around the vessel. A high degree of repeatability has been demonstrated that allows observation of changes due to the contents in the vessel. Signal traces are processed to yield frequency spectra that characterise the vessel and its contents. The observed eigenfrequencies are found to be in good agreement with those that are predicted using modal analysis from finite element modelling. Initial work has concentrated on the determination of liquid level in a cylindrical steel vessel. Results are within 98 % of the actual level