Nonlinear acoustic behavior of vented vessels in reference to pneumatic volume gauging

Pneumatic volume gauging offers many advantages in comparison with traditional fill-level measurement principles (e.g. tank shape, orientation of the tank and non-uniform surface structure of the fill material do not influence the result). Unfortunately, common pneumatic volume gauging methods work well for sealed tanks, but not for vented tanks. This property is a major drawback of pneumatic methods, but can be dealt by using an electroacoustic model approach for the tank system. This approach takes lumped elements to model the acoustic behavior of the system. In traditional approaches the lumped elements are assumed to be constant. However, practical measurements show a nonlinear behavior of the system. Therefore this work investigates the cause of the nonlinear behavior in theory. Measurements depict the nonlinear behavior and confirm the theoretical considerations.