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Device and method for determining the moisture content of material

  • US 5,845,529 A
  • Filed: 12/31/1996
  • Issued: 12/08/1998
  • Est. Priority Date: 07/18/1995
  • Status: Expired due to Term
First Claim
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1. A device for measuring the moisture content of a module of material, the module featuring a structure, the device comprising:

  • (a) a source of microwave radiation for producing a microwave radiation source beam, at least a portion of said source being located on one side of the module, such that at least a portion of said source beam is able to pass substantially completely through a portion of the module to form a passed source beam;

    (b) at least one microwave antenna located on an opposing side of the module, said antenna being spatially separated from said source such that said source beam must travel on a path selected from the group consisting of through the module and across the module, said antenna receiving an exit beam and said antenna producing an antenna signal, said exit beam being said source beam after a transition from said source to said antenna, such that at least a portion of said exit beam is said passed source beam;

    (c) a conveyor for conveying the module between said source and said antenna, such that a plurality of antenna signals, a plurality of source beams and a plurality of exit beams are produced;

    (d) an attenuation unit for receiving a first portion of each of said plurality of antenna signals and for measuring an attenuation of each of said plurality of antenna signals;

    (e) a phase shift determiner for receiving a portion of each of said plurality of said source beams and a second portion of each of said plurality of antenna signals and for determining a phase shift between each of said plurality of said source beams and each of said plurality of antenna signals, said phase shift determiner including;

    (i) a raw phase shift measurer for determining a raw phase shift of each of said plurality of said source beams and each of said plurality of antenna signals; and

    (ii) a phase region determiner for determining a phase region of said raw phase shift from said attenuation of each of said plurality of said antenna signals and from an empirical curve determined for the structure of the module and the type of material, said empirical curve showing a relationship between said attenuation and said phase region, said phase region having a value in a range of from 2π

    (n-1) to 2π

    n, n being determined by counting a number of cycles of said raw phase shift as the module is conveyed between said source antenna and said receiving antenna, such that said phase region determiner is able to produce a corrected phase shift according to said value of n; and

    (e) a moisture determiner for determining a moisture content of the module from said corrected phase shift and said attenuation.

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