US3720890A - Waveguide for moisture measurement - Google Patents

Waveguide for moisture measurement Download PDF

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Publication number
US3720890A
US3720890A US00160928A US3720890DA US3720890A US 3720890 A US3720890 A US 3720890A US 00160928 A US00160928 A US 00160928A US 3720890D A US3720890D A US 3720890DA US 3720890 A US3720890 A US 3720890A
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United States
Prior art keywords
waveguide
slots
channel
propagation channel
grooves
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00160928A
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English (en)
Inventor
J Anderson
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Rank Cintel Ltd
NDC Technologies Ltd
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Rank Organization Ltd
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Assigned to INFRARED ENGINEERING LIMITED reassignment INFRARED ENGINEERING LIMITED ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: RANK ORGANISATION PUBLIC LIMITED COMPANY, THE
Assigned to RANK CINTEL LIMITED, 6 CONNAUGHT PLACE, LONDON, W2 2EX, ENGLAND reassignment RANK CINTEL LIMITED, 6 CONNAUGHT PLACE, LONDON, W2 2EX, ENGLAND ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: RANK ORGANISATION PLC, THE
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/30—Auxiliary devices for compensation of, or protection against, temperature or moisture effects ; for improving power handling capability
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G01N22/04—Investigating moisture content

Definitions

  • ABSTRACT Waveguide for use in moisture measurement comprises two plates with the propagation channel partly formed in each'.
  • both plates Preferably both plates have a series of spaced grooves or slots at preferably both sides of the channel and transverse thereto to reduce longitudinal excitation of electromagnetic waves outside the channel.
  • any moisture in a sheet material lying between the halves of a split waveguide will alternativeuate the micro waves propagated along the waveguide propagation channel.
  • the energies of the micro waves before and after contact with the sheet material give the attenuation and hence an indication of the moisture content in the sheet material.
  • the sheet material may be stationary or moving, the guide being appropriately designed in the latter case.
  • a disadvantage of such a waveguide is that unless the sheet material fills the gap between the guide plates exactly, then there is always the possibility that electromagnetic energy will radiate from the propagation channel allowing the electric field to excite longitudinally in the gap between the plates and outside the propagation channel, thus causing electromagnetic energy to propagate in the area surrounding the propagation channel. Such propagation energy may be lost by radiation or may couple into another part of the waveguide causing errors in moisture determination.
  • a waveguide comprising two plates arranged in face to face relationship with the propagation channel partly formed in each of the opposed faces of the plates and wherein at least one of said opposed faces has slots or grooves which are spaced in the direction of the length of the propagation channel, which are located at at least one side of the propagation channel, and each of which extends in a direction transverse to the direction of the length of the propagation channel but does not penetrate such channel so that said slots can act to reduce or eliminate longitudinal excitation of electromagnetic waves outside the propagation channel.
  • each of said slots or grooves has a curved base which leads to the surface of the waveguide plate, one end of such base terminating close to the propagation channel.
  • each waveguide plate has such slots or grooves.
  • dielectric material holding channel extending transversely of, and passing through, the grooves or slots.
  • each dielectric holding channel there is a lossy dielectric material in the or each dielectric holding channel, the transverse slots or grooves passing through such material.
  • FIG. 1 is a sectional elevation taken through one plate ofa split waveguide
  • FIG. 2 is a diagrammatic sectional elevation taken through the ,part of waveguide when the plates are operatively positioned in relation to the sheet material to be tested;
  • FIG. 3 is a perspective view of part of one of the waveguide plates, and shows the plate face in which the propagation channel is partly formed.
  • waveguide plate shown therein is represented by the reference numeral 10 and a part of the propagation channel formed in such plate 10 by the reference numeral 12, such channel 12 extending in a direction normal to the plane containing FIG. 1.
  • the three channel sections 12 are joined end to end to form a continuous propagation channel.
  • dielectric material holding channels 14 each containing the rectangular section rod of dielectric material 4.
  • the channels 14 are formed on the same side of the plate 10 as the channel sections 12.
  • choke channels .3 Interspaced between the channel sections 12 and channels 14 are choke channels .3 which are parallel both to the channel sections 12 and the channels 14 and are also formed in the same face of the plate as sections 12 and channels 14.
  • each channel section 12 Extending transversely from each side of each channel section 12 is a series of spaced slots 5 which extend through the dielectric material 4 as shown in FIG. 3 and each of which is defined by grill walls and has a curved base of the form shown in the drawings so that the depth of the slot decreases to zero at'each end and the along the edges of the channel sections 12 are external to the electromagnetic path of the waveguide and interupt the longitudinal conducting, surface immediately external to the aforesaid channel.
  • the other plate 16 of the waveguide has been shown as not having any choke channels 3 but it is to be appreciated that this omission is optional and if desired the plate: 16 may be provided with such channels 3 and therefore, be identical to plate 10. It is also to be noted that in FIG. 3 only two choke channels 3 have been shown. This is simply in the interest of clarity of the drawing. p
  • a waveguide comprising two plates arranged in face to face relationship with the propagation channel partly formed in each of the opposed faces of the plates and wherein at least one of said opposed faces has slots or grooves which are spaced in the direction of the length of the propagation channel, which are located at at least one side of the propagation channel, and each of which extends in a direction transverse to the direction of the length of the propagation channel but does not penetrate such channel so that said slots act to reduce or eliminate longitudinal excitation of electromagnetic waves outside the propagation channel.
  • a waveguide according to claim 1 wherein there is a series of such slots or grooves at each side of the propagation channel.
  • each of said slots or grooves is defined by side walls and a curved base and diminishes to zero depth at each end,
  • each waveguide plate has such slots or grooves.
  • a waveguide according to claim 4 wherein there is at least one choke channel in at least one of the waveguide plates extending transversely of and through the transverse grooves or slots.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US00160928A 1970-07-08 1971-07-08 Waveguide for moisture measurement Expired - Lifetime US3720890A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3311570 1970-07-08

Publications (1)

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US3720890A true US3720890A (en) 1973-03-13

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US (1) US3720890A (de)
DE (1) DE2134147C3 (de)
GB (1) GB1318049A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3988702A (en) * 1974-06-01 1976-10-26 Licentia Patent-Verwaltungs-G.M.B.H. Waveguide section for connecting rectangular waveguide with elliptical waveguide
US4507632A (en) * 1981-08-21 1985-03-26 Thomson-Csf Electromagnetic wave switch
US4646000A (en) * 1984-11-08 1987-02-24 The Yellow Springs Instrument Company Method and apparatus for measuring soil salinity
US4862186A (en) * 1986-11-12 1989-08-29 Hughes Aircraft Company Microwave antenna array waveguide assembly
WO1990004167A1 (en) * 1988-10-05 1990-04-19 Sri International Composition monitor and monitoring process using impedance measurements
US6499346B1 (en) * 1998-03-28 2002-12-31 Endress + Hauser Gmbh + Co. Filling level measuring device operating with microwaves
WO2009078814A1 (en) * 2007-12-18 2009-06-25 Soon Yim Tan A spaced plate waveguide probe and method for dielectric measurements

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4739249A (en) * 1987-04-23 1988-04-19 Imatran Voima Oy Method and apparatus for the measurement of the properties of sheet- or foil-like materials of low electrical conductivity

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB844856A (en) * 1956-09-04 1960-08-17 Ici Ltd Wave-guide choke couplings
US3586971A (en) * 1969-02-10 1971-06-22 Canadian Patents Dev Microwave apparatus for ascertaining changes in dielectric properties utilizing a slow wave structure

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB844856A (en) * 1956-09-04 1960-08-17 Ici Ltd Wave-guide choke couplings
US3586971A (en) * 1969-02-10 1971-06-22 Canadian Patents Dev Microwave apparatus for ascertaining changes in dielectric properties utilizing a slow wave structure

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Summerhill, S.; Microwaves In The Measurement of Moisture Instrument Review; Oct. 1967; pp 419 422 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3988702A (en) * 1974-06-01 1976-10-26 Licentia Patent-Verwaltungs-G.M.B.H. Waveguide section for connecting rectangular waveguide with elliptical waveguide
US4507632A (en) * 1981-08-21 1985-03-26 Thomson-Csf Electromagnetic wave switch
US4646000A (en) * 1984-11-08 1987-02-24 The Yellow Springs Instrument Company Method and apparatus for measuring soil salinity
US4862186A (en) * 1986-11-12 1989-08-29 Hughes Aircraft Company Microwave antenna array waveguide assembly
WO1990004167A1 (en) * 1988-10-05 1990-04-19 Sri International Composition monitor and monitoring process using impedance measurements
US5103181A (en) * 1988-10-05 1992-04-07 Den Norske Oljeselskap A. S. Composition monitor and monitoring process using impedance measurements
AU638217B2 (en) * 1988-10-05 1993-06-24 Den Norske Stats Oljeselskap A.S. Composition monitor and monitoring process using impedance measurements
US6499346B1 (en) * 1998-03-28 2002-12-31 Endress + Hauser Gmbh + Co. Filling level measuring device operating with microwaves
WO2009078814A1 (en) * 2007-12-18 2009-06-25 Soon Yim Tan A spaced plate waveguide probe and method for dielectric measurements

Also Published As

Publication number Publication date
GB1318049A (en) 1973-05-23
DE2134147A1 (de) 1972-01-13
DE2134147C3 (de) 1980-07-10
DE2134147B2 (de) 1979-10-18

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Legal Events

Date Code Title Description
AS Assignment

Owner name: INFRARED ENGINEERING LIMITED, BLUE MILL, WOODHAM W

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:RANK ORGANISATION PUBLIC LIMITED COMPANY, THE;REEL/FRAME:004508/0415

Effective date: 19850215

AS Assignment

Owner name: RANK CINTEL LIMITED, 6 CONNAUGHT PLACE, LONDON, W2

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:RANK ORGANISATION PLC, THE;REEL/FRAME:004810/0335

Effective date: 19871028