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

• Current Assignee: Malcam Ltd.
• Original Assignee: Malcam Ltd.
• Inventors: Moshe, Danny S., Greenwald, Alexander
• Primary Examiner(s): Williams, Hezron E.
• Application Number:
  US08/777,872
• Time in Patent Office: 707 Days
• Field of Search: 73/73, 73/29.01, 324/640, 324/643
• US Class Current: 73/73
• CPC Class Codes: G01N 22/04 Investigating moisture content
• CPC Class Codes: G01N 9/24 by observing the transmission of wave or particle radiation through the material

Abstract

A device for measuring the moisture content of a module of material, including: (a) a source of microwave radiation for producing a microwave radiation source beam, at least a portion of the source being located on one side of the module; (b) at least one microwave antenna located on an opposing side of the module for receiving an exit beam and for producing an antenna signal, the exit beam being the source beam after a transition from the source to the antenna; (c) an attenuation unit for receiving a first portion of the antenna signal and for measuring an attenuation of the antenna signal; (d) a phase shift determiner for receiving a portion of the source beam and a second portion of the antenna signal and for determining a phase shift of the source beam and the antenna signal, the phase shift determiner including: (i) a raw phase shift measurer for determining a raw phase shift of the source beam and the antenna signal; and (ii) a phase region determiner for determining a phase region of the raw phase shift from the attenuation and producing a corrected phase shift; and (e) a moisture determiner for determining a moisture content of the module from the corrected phase shift and the attenuation.

Claims

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.

2. The device of claim 1, wherein said attenuation unit further includes:

(a) an attenuation measurer for measuring an amplitude of said antenna signal, for comparing said attenuation to an amplitude of a reference signal of a constant amplitude, and for determining a difference between said constant amplitude of said reference signal and said amplitude of said antenna signal; and

(b) an attenuator for attenuating said antenna signal according to said difference.

3. The device of claim 1, wherein said phase region determiner further includes an empirical curve for determining said phase region from said attenuation, said phase region having a value in a range of from 2π

(n-1) to 2π

n, such that said phase region determiner is able to determine a value for n from said empirical curve and from said attenuation.

4. The device of claim 1, wherein:

(a) said microwave radiation source further includes;

(i) a first source antenna for producing and focussing said source beam such that said source beam passes through a lower portion of the module;

(ii) a second source antenna for producing and focusing said source beam such that said source beam passes through a lower portion of the module, and

(b) said at least one receiving antenna is a first receiving antenna and a second receiving antenna, and said receiving antenna includes a switch, such that said first receiving antenna produces said antenna signal when said first source antenna produces and focusses said source beam, and said second receiving antenna produces and focusses said antenna signal when said second source antenna produces and focusses said source beam.

5. The device of claim 1, wherein said microwave radiation source further includes an electric field director for manipulating a direction of an electric field of said source beam relative to the module, such that said direction of said electric field at least partially causes a magnitude of said attenuation and a magnitude of said phase shift.

6. The device of claim 1, wherein said moisture determiner further includes:

(a) a temperature sensor for determining a temperature of the module;

(b) a module type input for inputting a type of the module; and

(c) a normalizer for determining the moisture content from said temperature, said type, said corrected phase shift and said attenuation.

7. The device of claim 1, further including:

(a) a conveyor for conveying the module, such that multiple moisture measurements are made; and

(b) an averager for averaging said multiple moisture measurements.

8. The device of claim 1, wherein the material in the module has a substantially irregular structure.

9. The device of claim 1, wherein said phase shift determiner receives a plurality of portions of said source beam and a plurality of portions of said antenna signal, such that said phase region of said raw phase shift is determined by counting a number of phase shift cycles, each phase shift cycle including values of said raw phase shift in a range from 0 to 2π

.

10. The device of claim 1, wherein the module is selected from the group consisting of bale and case, and the structure of the material is substantially irregular.

11. The device of claim 1, wherein the module is selected from the group consisting of a bale and a case.

12. The device of claim 11, wherein the module is said bale and the material is selected from the group consisting of tobacco, cotton, paper, processed wood, tea and synthetic fibers.

13. The device of claim 11, wherein the module is said case and the material is selected from the group consisting of cotton, tobacco, tea and synthetic fibers.