System for measuring amount of specific substance mixed in material under measurement and electrode rod for measurement

• US 20020060576A1
• Filed: 07/10/2001
• Published: 05/23/2002
• Est. Priority Date: 07/13/2000
• Status: Active Grant

• Current Assignee: National Research Institute For Earth Science and Disaster Prevention
• Original Assignee: National Research Institute For Earth Science and Disaster Prevention
• Inventors: Tominaga, Masaki
• Granted Patent: US 6,507,201 B2
• Time in Patent Office: Days
• US Class Current: 324/715
• CPC Class Codes: G01N 27/048 for determining moisture content of the material
• CPC Class Codes: G01N 33/246 for water content

Abstract

A measuring system has at least four electrodes and an electric current measuring resistance placed in a material under measurement in a desired manner. A power supply supplies an alternating current between two of the electrodes through the resistance. A current measuring unit measures an electric current flowing through the resistance. A voltage measuring unit measures an electric potential difference between electrodes other than the electrodes supplied with the alternating current. A computing unit obtains a conductivity on the basis of the measured electric current and electric potential difference, together with a coefficient determined by the manner in which the electrodes are placed, and performs conversion based on calibration data to obtain the amount of a specific substance mixed in the material under measurement. An electrode rod has a distal end member formed from a cylindrical member, one end of which is formed into a conical shape. The cylindrical member is integrally formed at the other end thereof with an inner cylindrical portion having an outer diameter smaller than the outer diameter of the cylindrical member by an amount corresponding to the wall thickness of the cylindrical member. The electrode rod further has a plurality of annular electrodes and a plurality of spacers, each having an inner diameter corresponding to the outer diameter of the inner cylindrical portion. A cable lead-in opening is provided in the wall surface of the inner cylindrical portion. The annular electrodes are fitted onto the outer periphery of the inner cylindrical portion one after another at spacings determined by the spacers, and cables are led to the annular electrodes through the cable lead-in opening.

Claims

1. A system for measuring an amount of a specific substance mixed in a material under measurement, said system comprising:

at least four electrodes placed in the material under measurement in a desired manner;

a resistance for measuring an electric current placed in said material under measurement together with said electrodes;

a power supply for supplying an alternating current between two of said at least four electrodes through said resistance;

current measuring means for measuring an electric current flowing through said resistance;

voltage measuring means for measuring an electric potential difference between electrodes of said at least four electrodes other than the electrodes supplied with the alternating current from said power supply; and

computing means for obtaining a conductivity on a basis of the electric current measured with said current measuring means, the electric potential difference measured with said voltage measuring means, and a coefficient determined by a manner in which said at least four electrodes are placed, and for subjecting said conductivity to conversion based on calibration data to obtain an amount of said specific substance of interest mixed in said material under measurement.

2. The system of claim 1, wherein said at least four electrodes and said resistance are supported together as one unit on a support and placed in the material under measurement in a desired manner.

3. The system of claim 2, wherein said support comprises at least one plate- or rod-shaped member.

4. An electrode rod for measuring conductivity or resistivity by supplying an alternating current into a mixed material and measuring a resulting voltage using a group of one resistance and four electrodes, said electrode rod comprising:

a distal end member formed from a cylindrical member, one end of which is formed into a conical shape, said cylindrical member being integrally formed at the other end thereof with an inner cylindrical portion having an outer diameter smaller than an outer diameter of said cylindrical member by an amount corresponding to a wall thickness of said cylindrical member;

a plurality of annular electrodes each having an inner diameter corresponding to the outer diameter of said inner cylindrical portion;

a plurality of spacers each having an inner diameter corresponding to the outer diameter of said inner cylindrical portion; and

a cable lead-in opening provided in a wall surface of said inner cylindrical portion;

wherein said plurality of annular electrodes are fitted onto an outer periphery of said inner cylindrical portion one after another at spacings determined by said spacers, and cables are led to said annular electrodes through said cable lead-in opening.

6. The electrode rod of claim 4 or 5, wherein said plurality of spacers include a spacer having a mounting portion for mounting a resistance for detecting an electric current on a wall surface thereof.

9. The electrode rod of claim 4, 5 or 7, wherein said annular electrodes each have a projection formed on an outer periphery thereof.

5. An electrode rod for measuring conductivity or resistivity by supplying an alternating current into a mixed material and measuring a resulting voltage using a group of one resistance and four electrodes, said electrode rod comprising:

a distal end member formed from a cylindrical member, one end of which is formed into a conical shape, said cylindrical member being integrally formed at the other end thereof with an inner cylindrical portion having an outer diameter smaller than an outer diameter of said cylindrical member by an amount corresponding to a wall thickness of said cylindrical member;

a plurality of annular electrodes each having an inner diameter corresponding to the outer diameter of said inner cylindrical portion;

a plurality of spacers each having an inner diameter corresponding to the outer diameter of said inner cylindrical portion;

a coupling cylindrical member having a same outer diameter as the outer diameter of said inner cylindrical portion, said coupling cylindrical member being integrally formed at one end thereof with a coupling portion having an inner diameter corresponding to said outer diameter; and

cable lead-in openings provided in respective wall surfaces of said inner cylindrical portion and coupling cylindrical member;

wherein said plurality of annular electrodes are fitted onto outer peripheries of said inner cylindrical portion and coupling cylindrical member one after another at spacings determined by said spacers, and cables are led to said annular electrodes through said cable lead-in openings, and further said inner cylindrical portion is coupled with said coupling cylindrical member to form a multi-stage structure.

7. An electrode rod for measuring conductivity or resistivity by supplying an alternating current into a mixed material and measuring a resulting voltage using a group of one resistance and four electrodes, said electrode rod comprising:

a cylindrical member with a conical distal end;

four annular electrodes fixed on an outer periphery of said cylindrical member at predetermined spacings; and

a resistance for detecting an electric current, said resistance being fixed between said annular electrodes.

8. The electrode rod of claim 7, wherein a spacing between second and third annular electrodes of said four annular electrodes is enlarged, and said resistance is fixed between said second and third annular electrodes.