one heating transistor 11 for example a type buz 80 by the siemens company the dissipation heat of which advantageously heats up the resonator housing preferably via the environmental temperature the control system itself is not shown in fig2 but is known to the person skilled in the art a thin layer of gold 12 is deposited on the surfaces forming the boundaries of inside space 7 of resonator housing 4 1 and preferably also on the line sensor 21 which is an open ring in this case this gold layer reliably prevents corrosion which reduces the measuring value constancy and simultaneously prevents a damaging side effect on the skin owing to the high electrical conductance the resonator housing 4 1 advantageously is also gold plated from the outside to prevent corrosion to prevent a soiling of the interior space 7 that would impair the measuring result a protective tube 13 that advantageously consists of a substance of the poly aryl ether ketone paek group e g poly ether aryl ketone paek is used to mechanically seal the interior space 7 against the cigarette rope 1 and any dirt particles conveyed along the protective tube 13 can be expanded in the shape of a funnel at one of its ends at which the rope 1 enters the resonator housing 4 for reasons of clarity this is not shown in fig2 outside of the interior space 7 the resonator housing 4 1 extends on both sides in the shape of a tube toward the outside 14.