The present invention relates to a device for determining the filling level of a filling material in a container, having a signal-generating unit which generates measuring signals, having an input coupling unit and having an antenna. An analog circuit is formed with the use of a thin film transistor including an oxide semiconductor which has a function as a channel formation layer, has a hydrogen concentration of 5\xd71019 atomscm3 or lower, and substantially functions as an insulator in the state where no electric field is generated. The panel is substantially planar and has a bottom side and a top side facing and spaced apart from the lower surface. One of the ingredients can be a dairy product such as milk and the other can be water.