It is now well known that acoustic plate wave devices are very promising as gravimetric sensors in liquid phase as well as liquid properties sensors. Here, a model based on the effective permittivity function is developed to take into account the multi-layered configuration of these devices operating in liquid phase. Indeed, for gravimetric applications, a three-layered configuration is implemented: the piezoelectric plate, the elastic solid film and the semi-infinite liquid medium. The predictions of the model for an increasing solid film thickness are compared with experimental measurements obtained by electrodeposition. For the determination of liquid properties, a two-layered configuration is appropriate: the piezoelectric plate loaded by the liquid medium. Here, particular attention is paid to the effect of the density and the viscosity of the liquid medium on the device response. The theoretical results are compared with measurements performed with aqueous glycerol solutions, whose density and viscosity increase with concentration of glycerol. For high concentrations, the Maxwellian behavior of the aqueous glycerol solutions allows to determine the shear rigidity modulus of glycerol.