Microwave Non-contact Sensor for On-Line Moisture Measurement of Laminate Paper

A microwave sensor, intended for on-line measurements of paper moisture, is presented in this paper. The sensor main body is a resonant structure, with a paper sheet passing through it. From the measurement of the resonant frequency and/or the quality factor of the resonator, the value of the humidity content of the paper can be obtained, with great accuracy. Very promising measurements have been carried out, leading to the use of the sensor at industrial level.