Multi-frequency microwave sensor for temperature independent measurement of moisture

摘要

Microwave techniques for measuring moisture and other properties of paper and related products without requiring an independent measurement of temperature are provided. A sensor directly measures the reflection or transmission of microwaves at a number of well-chosen frequencies so as to characterize the absorption spectrum of the product. The technique of measuring the parameters of a composition includes: (a) directing incident microwave radiation over a spectrum of wavelengths from an antenna upon the composition; (b) measuring the microwave radiation over the spectrum of wavelengths that emerges from the composition; (c) determining the reflected and/or transmitted transfer function; and (d) relating the transfer function of the composition to the parameters of the composition by applying a theoretic, calibrated, or hybrid model. The product moisture and temperature are extracted from the transfer function.

主权项

1. A method of measuring two or more parameters of a composition, which includes water, that comprises the steps of:
a. directing microwave radiation over a spectrum of wavelengths from an antenna to be incident upon the composition; b. measuring the microwave radiation over the spectrum of wavelengths that emerges from the composition; c. determining a reflected and/or transmitted transfer function of the composition over the spectrum of wavelengths; d. relating the determined transfer function of the composition over the spectrum of wavelengths to two or more parameters of the composition, that include water temperature and at least one of composition percent moisture or composition basis weight, by applying a model, with the proviso that an independent temperature measurement of the composition is not required; and e. predicting the water temperature and at least one of composition percent moisture or composition basis weight.