A new slot sensor for moisture content measurement of sheetlike materials

In this paper a two-port slot sensor for measuring the moisture content of sheetlike materials is proposed and analysed. The sensor is of the resonant type and it mainly consists on a section of a slot-line interacting with the material under test (MUT) by means of radiative near fields. The most important design aspects of the sensor are discussed in relation to the dispersive behaviour of the slot line and its radiative interaction with the MUT. The article deals with the full-wave numerical modelling of the interaction between the sensor and a moist felt, chosen as reference MUT. The parametric sensitivity to the distance between the slot radiating aperture and the MUT surface is also analysed, since in the industrial environment the monitoring of the moisture content is usually performed by linearly scanning the sensor over the material surface. Finally, a calibration and measuring procedure based on the use of a neural artificial network is suggested and its accuracy is numerically evaluated.