Abstract: Apparatus for ascertaining the mass and/or the moisture content of successive increments of a running rod containing tobacco and/or filter material for tobacco smoke has a resonator housing with a cylindrical internal chamber which is disposed between an inlet and an outlet and wherein the rod is exposed to microwaves. The housing is made of a metallic material having a low thermal expansion coefficient, and its internal surface is lined with gold or another corrosion resistant substance. A protective plastic tube establishes a path for the rod from the inlet, across the chamber and into the outlet of the resonator housing.

Abstract: Apparatus for ascertaining the mass and/or the moisture content of successive increments of a running rod containing tobacco and/or filter material for tobacco smoke has a resonator housing with a cylindrical internal chamber which is disposed between an inlet and an outlet and wherein the rod is exposed to microwaves. The housing is made of a metallic material having a low thermal expansion coefficient, and its internal surface is lined with gold or another corrosion resistant substance. A protective plastic tube establishes a path for the rod from the inlet, across the chamber and into the outlet of the resonator housing.

Abstract: Apparatus for ascertaining the mass and/or the moisture of succesive increments of a running rod containing tobacco and/or filter material for tobacco smoke having a resonator housing with a cylindrical internal chamber which is disposed between and inlet an outlet and wherein the rod is exposed to microwaves. The horsing is made of a metallic material having a low thermal expansion coefficient, and its internal surface is lined with gold or another corrosion resistant substance. A protective plastic tube establishes a path for the rod from the inlet, across the chamber and into the oulet of the resonator housing.

Abstract: At least one characteristic, such as the mass/density and/or moisture content and/or dielectric constant, of a substance (such as the rod-like tobacco filler of a continuously advancing cigarette rod or a continuously advancing rod-like filler of filter material for tobacco smoke) is ascertained by an evaluating circuit receiving high-frequency signals from a resonator arrangement which receives microwave signals at least at two different frequencies from one or more microwave generators. The substance is caused to advance through a dielectric resonator of the resonator arrangement, and the high-frequency signals are influenced by the substance. For example, the circuit can compare first and second curves of high-frequency signals which respectively are and are n ot influenced by a selected substance; the curves can have sloping flanks and each of the two frequencies can be allocated to a sloping flank of a curve.