considerations on contactless inductive paper moisture measurement

Abstract

At the end of the paper production process, reducing its moisture content is achieved by passing the finished product in continuous flow through an electric oven. This paper assumes humidity control, which in turn determine the electrical conductivity of the paper. The operating principle of non-contact method is: a transmitting coil Tx supplied with alternating current at an audio frequency is placed on the paper comes out of the oven. A reception coil Rx is located at a short distance, s, away from the Tx coil. The magnetic field varies in time and emission Tx coil induces circular currents of very low intensity in wet paper. These currents generate a secondary magnetic field Hs , which is sensed by the receiver Rx coil together with the magnetic field Hp. The ratio of the secondary magnetic field Hs and Hp primary magnetic field (Hs \ Hp) is directly proportional to the conductivity of the paper. Thus it is possible to build a device to measure the conductivity of paper contactless electromagnetic technique.