Device for detecting profile in refiner and method therefore

A fiber concentration measuring device, comprising:

• a first conductor body configured to detect the degree of fiber concentration of a fiber pad being pulped, during use of the device, in a grinding gap between refiner discs of a refiner, wherein the first conductor body comprises a first electric contact surface, wherein a refiner disc grinding surface of one of the refiner discs positioned opposite the first conductor body acts as a second electric contact surface, wherein the first electric contact surface is configured to provide an electrical contact with the second electric contact surface such that an electric current is transferred via the fiber pad material;
• a control unit configured to detect alteration of electrical resistivity or conductivity of the fiber pad material by measuring the electric current;
• and
• a second conductor body, wherein the first conductor body is connected in series with a first series resonance circuit and the second conductor body is connected in series with a second series resonance circuit, wherein the first series resonance circuit and second series resonance circuit are each configured to allow passage of the electric current to a desired frequency.