US3339137A - Moisture determining apparatus having adjacent electrode pairs driven outof-phase - Google Patents

Moisture determining apparatus having adjacent electrode pairs driven outof-phase Download PDF

Info

Publication number
US3339137A
US3339137A US380189A US38018964A US3339137A US 3339137 A US3339137 A US 3339137A US 380189 A US380189 A US 380189A US 38018964 A US38018964 A US 38018964A US 3339137 A US3339137 A US 3339137A
Authority
US
United States
Prior art keywords
electrodes
moisture
pair
wood
lumber
Prior art date
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
Application number
US380189A
Other languages
English (en)
Inventor
William D Perry
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Weyerhaeuser Co
Original Assignee
Weyerhaeuser Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Weyerhaeuser Co filed Critical Weyerhaeuser Co
Priority to US380189A priority Critical patent/US3339137A/en
Priority to DE19651673293 priority patent/DE1673293A1/de
Priority to FR11724A priority patent/FR1429739A/fr
Priority to NL6505335A priority patent/NL6505335A/xx
Priority to CH610365A priority patent/CH440767A/de
Priority to JP40028012A priority patent/JPS4833197B1/ja
Priority to SE06497/65A priority patent/SE331597B/xx
Priority to GB28131/65A priority patent/GB1117683A/en
Application granted granted Critical
Publication of US3339137A publication Critical patent/US3339137A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity

Definitions

  • Such meters are not fully satisfactory in performance since they are dependent upon wood density and thickness and are consequently quite sensitive to the distance between the wood surface and the electrodes. Thus these meters may not detect wet pockets in the middle of a two-inch thick sample of wood, and the accuracy is of a lower order whenever the electrode to wood distance varies as is the case with rough sawn lumber.
  • the capacitance type moisture meters described in my copending applications referred to above are used to measure the moisture in lumber traveling longitudinally through the meters or in only one portion of the lumber traveling laterally through the meter.
  • the present invention provides an improvement by expanding the meter to two or more pairs of shielded electrodes mounted a fixed distance apart with the Wood passing between each pair.
  • the use of two or more electrode pairs allows moisture to be detected in two or more portions of the lumber passing laterally through them.
  • the adjacent pairs of electrodes must be driven electrically out of phase to guarantee the presence of an electrical ground plane in the wood between electrode pairs.
  • the object of this invention to provide an apparatus for measuring the moisture content of materials which permits the materials to pass in a direction normal to the alignment of the electrode pairs to one another.
  • the moisture metering apparatus consists of two or more sensing heads which are mounted in a line normal to the direction of lumber is being conveyed past them.
  • Each sensing head consists of a pair of shielded electrodes mounted a fixed distance apart such that the wood sample to be metered passes between them without touching them. These electrodes are connected to any electrical circuit which allows the internal resistance which indicates the presence of water in the wood to be indicated as an output voltage.
  • the two shielded electrodes making up each sensing head are connected together electrically so that the volume between them is essentially a field-free region.
  • Each of the sensing heads is connected to the same power supply which drives adjacent heads 180 out of phase. This outof-phase drive forces the wood to a ground potential midway between the heads.
  • the output signals from each head can be combined to indicate either the average or maximum moisture content in the portions of the wood adjacent to each head.
  • FIGURE 1 is a perspective view showing a typical installation of this invention.
  • FIGURE 2 is a side elevation view of adjacent meter heads constructed in accordance with this invention.
  • FIGURE 3 is a schematic electrical diagram of the ele ments shown in FIGURE 2.
  • FIGURE 4 is an end elevation view of one moisture metering head made in accordance with this invention.
  • FIGURE is a schematic diagram of a conventional electrical circuit which can be used in the operation of a moisture meter made in accordance with this invention.
  • FIGURE 6 is a schematic diagram of a modified electrical circuit which may be used in controlling the moisture meter installation as taught by this invention.
  • FIGURE 1 shows a typical multiple head moisture meter installation 1 used for metering lumber as it is conveyed from one station to another in a lumber mill.
  • a suitable conveying means 3 causes the lumber 5 to be transported across the lower frame 6.
  • An upper frame 8 is supported above the path of the lumber 5 and aligned perpendicular to the direction that the lumber is conveyed. Aligned with the upper frames 8 are a number of moisture sensing head units 10, 20 and 30.
  • the first moisture sensing unit 10 comprises an upper electrode shield 11 and a lower electrode shield 12 with the upper electrode shield 11 being suspended from the upper frame 8 by means of support rods 13.
  • the lower electrode shield 12 is supported by the lower frame 6.
  • the first moisture sensing head unit 10 is electrically connected to the control unit 50 by means of upper electrode lead 14 and lower electrode lead 15, shown in dotted lines since it is below the lower frame 6.
  • a spray unit 45 which is supplied by a marking fluid container 46 through hose 47.
  • the spray unit 45 can be mounted on an extension of either of the upper electrode shields 11 or 21 or the second moisture sensing head unit and the container 46 may be supported by the upper frame 8.
  • the second moisture sensing head unit 20 has similar structural elements to those in the first moisture sensing unit 10.
  • the upper electrode shield 21 is suspended by means of support rods 23, which are, in turn, connected to the upper frame 8.
  • the lower electrode shield 22 is supported by the lower frame 6.
  • the upper electrode 27 is separated from the upper electrode shield 21 by means of insulation spacers 26, and is electrically connected to the control unit 50 by means of the upper electrode lead 24.
  • lower electrode 28 is separated by means of spacers 26 from the lower electrode shield 22 and electrically connected to a control unit 50 by means of lower electrode lead 25.
  • the lumber 5 is conveyed by means of conveying means 3 through the air gap between the first moisture sensing units upper and lower electrodes 17 and 18 and the second moisture sensing units upper and lower electrodes 27 and 28. It should be noted that there is no actual connection between the electrodes and the lumber.
  • the upper electrode shields 11 and 21 are grounded as are the lower electrode shields 12 and 22. It is also seen that in the first moisture sensing unit head 10, the upper and lower electrodes 17 and 18 are commonly connected to an electrical power source and thus the air gap between the electrodes 17 and 18 becomes a field-free region. In a similar manner, the pair of electrodes 27 and 28 in the second moisture sensing head unit 20 are electrically connected and a field-free region exists in the air gap between these electrodes. It should also be noted that the AC. power supply 51 through the transformer 52 provides a phase relationship between the adjacent moisture sensing units 10 and 20 such that the paired electrodes 17 and 18 are 180 out of phase with the paired electrodes 27 and 28.
  • C-10 represents the capacitance between the electrodes 17, 18 and the wood 5.
  • R-10 represents the internal resistance of the volume of wood between the field of electrodes 17, 18 and the ground g.
  • resistance R-20 and a capacitance C-20 As the wood 5 containing water is moved into the air volume between paired electrodes 17 and 18 and 27 and 28, an electrical charge is induced into wood 5. The amount of the charge induced depends on the conductivity, and hence the moisture content of the wood.
  • the moisture content of the lumber 5 can be measured regardless of whetherthe lumber 5 is rough or surfaced lumber. Since the electrodes 17 and 18 have the same electrical potential, the moisture sensing unit is relatively insensitive to the woods position in the space between these electrodes. This installation is especially sensitive to nonuniform moisture distributions resulting in water concentrations inside of a piece of lumber, and allows rapid measurement without physical contact with the lumbers surface.
  • the use of two or more electrode pairs, such as in units 10 and 20, allows the moisture to be detected in two or more portions of the lumber passing through them.
  • the adjacent pairs of electrodes 17 and 18 and 27 and 28 being driven out of phase guarantees the presence of an electrical ground plane in the wood between the electrode pairs and erroneous signals due to local interference are eliminated by this positive ground.
  • FIGURE 4 shows an end elevation view of the third moisture sensing unit head 30.
  • the upper electrode shield 31 is suspended by means of support rods 33 and physically separated and insulated from the upper electrode 37 by means of spacers 36.
  • the upper electrode 37 is connected to the control unit 50 by means of the upper electrode lead 34.
  • the lower electrode shield 32 is supported by the lower frame 6 and is electrically insulated from the lower electrode 38, which is electrically connected to the control unit 50 by means of lower electrode lead 35.
  • the upper support rods can be attached to the upper frame by means of hinges 39.
  • a cushion 40 may be interposed between the upper frame 8 and the support rods 33 .to absorb the shock when the support rods 33 return to the normal position after being deflected.
  • FIGURE 5 there is shown an electrical diagram of some of the control components which may be used to control the moisture sensing installation 1.
  • the AC power source 51 through the transformer 52 drives each of the adjacent control bridges which corresponds to the adjacent moisture sensing unit heads 10, 20 and 30, out of phase.
  • a typical bridge is composed of a series connection between a ground g and a point 10b, having within it a variable capacitor VC-10. From point 10b to the high potential is a standard capacitor Cs. Continuing around the bridge from the high potential is an identical standard capacitor Cs which connects the high potential to another pick-off point 10a.
  • Ct-10 is a metering capacitor connected in parallel through the air gap with the portion of the lumber 5 electrically shown as the capacitor C-10 and resistor R-10 in series.
  • the sensitivity of the control is dependent upon the settings in the amplifier such that the output signals can be used to energize the spray unit 45, if any one signal goes over a maximum amount allowed or if all three signals combined go over a maximum amount allowed or any combination of such signals. These signals could be used to ring a bell, open a conveyor pocket, or any other desired way to indicate the presence of a wet board.
  • FIGURE 6 there is shown an equivalent control circuit to that shown in FIGURE 5, with similar units being designated by .the same identifying symbols.
  • the novel feature of this particular circuit lies in the fact that it is a straight line bridge running from the high potential through the first standard capacitor Cs, through the point a, through the meter capacitance Ct-lt) to the ground g and continuing through a variable capacitor VC-10 to point 101), through the standard capacitor Cs to the low potential.
  • the difference between the potential 10a and 10b is transmitted through the nominal resistances Rn to a preamplifier giving the signal difference 10b-10a.
  • the bridge output side may be modified as shown in the bridge circuit for the third moisture sensing unit head 30.
  • Addition of a potentiometer 53 can provide a resistance balance between the points 3011 and 30b on the output side of the circuit ,to the preamplifier 30b30a.
  • the novel feature or advantage of the equivalent circuit shown in FIGURE 6 is that standard electronic components, rather than higher cost specialty items, can be used throughout this circuit.
  • the amplifiers used in the circuit shown in FIGURE 6 may be simple AC amplifiers, whereas the amplifiers required in the circuit shown in FIGURE 5 must be differential amplifiers.
  • This installation is sensitive to nonuniform moisture distribution within a portion of the ltunber, is rugged in design, reliable, accurate, and flexible in use. It can be used to measure the average moisture content within one portion of lumber or the maximum moisture content in all of the portions, or any one portion of the lumber metered.
  • the electrical control is likewise flexible and easily maintained.
  • a moisture meter apparatus comprising in combination:
  • first and second pair of electrodes adjacent to said first electrodes electrical power source means having first and second leads, said first lead connected to said first pair of electrodes, said second lead connected to said second pair of electrodes,
  • conveyor means for conveying material to and from said first and second pair of electrodes
  • said first and second pair of electrodes having opposite electrodes of each pair being displaced one from another a distance to establish a field-free region between each other through which the material being metered passes,
  • each of said pairs of electrodes being electrically driven, by said power source out of phase from the adjacent pair of electrodes,
  • control means electrically connected to each of said pairs of electrodes and responsive to electrical currents from said electrodes to indicate the moisture content of said material passing between said adjacent electrode pairs.
  • said adjacent pair of electrodes is aligned on an axis normal to the direction in which said material being metered passes said electrodes.
  • the moisture meter of claim 1 including:
  • said power means includes an alternating current source providing, through said first and second leads, for a high potential, a low potential connection, and, through a ground lead, a ground connection,
  • said pairs of electrodes are included in a capacitor voltage divider means, said capacitor voltage divider means includes at least two capacitor voltage dividers,
  • one of said dividers includes in series from said high potential lead a standard capacitor and a first capacitor and in series from said groundlead a variable capacitor and another standard capacitor to said low potential lead, said first capacitor having one plate formed by one of said pairs of electrodes and another plate formed by a first grounded shield means for said one of said electrode pairs,
  • a second divider adjacent said one divider includes in series from said high potential lead a standard capacitor and a variable capacitor to said ground lead and in series from said ground lead a second capacitor and another standard capacitor to said low potential lead, said second capacitor having one plate formed by said adjacent pair of electrodes and another plate formed by a second grounded shield means for said adjacent pair of electrodes,
  • control means includes an output means having at least one amplifier which is electrically connected through nominal resistances to one of said dividers at one point between said electrode capacitor and one of said standard capacitors and at a second point between said variable capacitor and another of said standard capacitors.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth 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)
US380189A 1964-07-03 1964-07-03 Moisture determining apparatus having adjacent electrode pairs driven outof-phase Expired - Lifetime US3339137A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US380189A US3339137A (en) 1964-07-03 1964-07-03 Moisture determining apparatus having adjacent electrode pairs driven outof-phase
DE19651673293 DE1673293A1 (de) 1964-07-03 1965-03-29 Feuchtigkeitsmessgeraet
FR11724A FR1429739A (fr) 1964-07-03 1965-04-02 Appareil hygrométrique
NL6505335A NL6505335A (enrdf_load_stackoverflow) 1964-07-03 1965-04-27
CH610365A CH440767A (de) 1964-07-03 1965-05-03 Feuchtigkeitsmessgerät für ein Materialstück
JP40028012A JPS4833197B1 (enrdf_load_stackoverflow) 1964-07-03 1965-05-14
SE06497/65A SE331597B (enrdf_load_stackoverflow) 1964-07-03 1965-05-18
GB28131/65A GB1117683A (en) 1964-07-03 1965-07-02 Improvements in or relating to apparatus for measuring the moisture content of materials

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US380189A US3339137A (en) 1964-07-03 1964-07-03 Moisture determining apparatus having adjacent electrode pairs driven outof-phase

Publications (1)

Publication Number Publication Date
US3339137A true US3339137A (en) 1967-08-29

Family

ID=23500249

Family Applications (1)

Application Number Title Priority Date Filing Date
US380189A Expired - Lifetime US3339137A (en) 1964-07-03 1964-07-03 Moisture determining apparatus having adjacent electrode pairs driven outof-phase

Country Status (7)

Country Link
US (1) US3339137A (enrdf_load_stackoverflow)
JP (1) JPS4833197B1 (enrdf_load_stackoverflow)
CH (1) CH440767A (enrdf_load_stackoverflow)
DE (1) DE1673293A1 (enrdf_load_stackoverflow)
GB (1) GB1117683A (enrdf_load_stackoverflow)
NL (1) NL6505335A (enrdf_load_stackoverflow)
SE (1) SE331597B (enrdf_load_stackoverflow)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3444463A (en) * 1965-11-26 1969-05-13 Coulter Electronics Particle analyzing apparatus and method utilizing multiple apertures
US3448381A (en) * 1966-07-05 1969-06-03 William D Perry Portable non-contact moisture meter including electrodes driven 180 out of phase
US3523243A (en) * 1967-10-31 1970-08-04 Delmer W Wagner Moisture measurement device insensitive to thickness of material under test
US3523246A (en) * 1965-04-27 1970-08-04 Brian Reginald Hall Method of and apparatus for testing a laminar material for irregularities of thickness
US3593128A (en) * 1969-05-21 1971-07-13 Weyerhaeuser Co Moisture-content-measuring system employing a separate bridge circuit for each sensing electrode thereof
US4377783A (en) * 1979-10-15 1983-03-22 Wagner Delmer W Moisture detector
WO1984001220A1 (en) * 1982-09-22 1984-03-29 Weyerhaeuser Co Method of measuring moisture content of dielectric materials
US4713603A (en) * 1983-11-02 1987-12-15 Den Norske Stats Oljeselskap A.S. Apparatus for the measurement of the fraction of gas in a two-component fluid flow comprising a liquid and a gas in mixture
US4733166A (en) * 1986-03-17 1988-03-22 Wagner Delmer W Apparatus for measuring the moisture content of moving materials
US4782282A (en) * 1986-07-09 1988-11-01 Dickey-John Corporation Capacitive-type seed sensor for a planter monitor
NL1005956C2 (nl) * 1997-05-02 1998-11-03 Arnold Brookhuis Textieltechni Inrichting voor het meten van de vochtigheid van een materiaal, bijvoorbeeld hout.
WO2005103661A1 (en) * 2004-04-22 2005-11-03 Damsten Leif Daniel Method and apparatus for measuring the moisture content of a block of timber
US20100231231A1 (en) * 2009-03-10 2010-09-16 Microtec S.R.L. Method for calibrating apparatuses for determining the moisture content of products based on capacitive measurements, and device for simulating the dielectric properties of products, such as wood, for use in this method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996032634A1 (fr) * 1995-04-13 1996-10-17 Sumitomo Forestry Co., Ltd. Capteur d'humidite pour produits en bois et dispositif automatique de mesure de la teneur en humidite
JP6457427B2 (ja) 2016-04-15 2019-01-23 ファナック株式会社 ワイヤ放電加工装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1924087A (en) * 1931-09-29 1933-08-29 Atlantic Prec Instr Company Method and means for measuring and indicating properties of conductors
US2428700A (en) * 1943-09-17 1947-10-07 Wolgen Company Capacitative feed-back device for electrical testing
US3020476A (en) * 1958-05-26 1962-02-06 Honeywell Regulator Co Measuring apparatus
US3039051A (en) * 1959-08-12 1962-06-12 Zellweger Uster Ag Apparatus for gaging textile materials
CA673684A (en) * 1963-11-05 A. Sherman Charles Moisture detector

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA673684A (en) * 1963-11-05 A. Sherman Charles Moisture detector
US1924087A (en) * 1931-09-29 1933-08-29 Atlantic Prec Instr Company Method and means for measuring and indicating properties of conductors
US2428700A (en) * 1943-09-17 1947-10-07 Wolgen Company Capacitative feed-back device for electrical testing
US3020476A (en) * 1958-05-26 1962-02-06 Honeywell Regulator Co Measuring apparatus
US3039051A (en) * 1959-08-12 1962-06-12 Zellweger Uster Ag Apparatus for gaging textile materials

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3523246A (en) * 1965-04-27 1970-08-04 Brian Reginald Hall Method of and apparatus for testing a laminar material for irregularities of thickness
US3444463A (en) * 1965-11-26 1969-05-13 Coulter Electronics Particle analyzing apparatus and method utilizing multiple apertures
US3448381A (en) * 1966-07-05 1969-06-03 William D Perry Portable non-contact moisture meter including electrodes driven 180 out of phase
US3523243A (en) * 1967-10-31 1970-08-04 Delmer W Wagner Moisture measurement device insensitive to thickness of material under test
US3593128A (en) * 1969-05-21 1971-07-13 Weyerhaeuser Co Moisture-content-measuring system employing a separate bridge circuit for each sensing electrode thereof
US4377783A (en) * 1979-10-15 1983-03-22 Wagner Delmer W Moisture detector
WO1984001220A1 (en) * 1982-09-22 1984-03-29 Weyerhaeuser Co Method of measuring moisture content of dielectric materials
US4580233A (en) * 1982-09-22 1986-04-01 Weyerhaeuser Company Method of measuring moisture content of dielectric materials
US4713603A (en) * 1983-11-02 1987-12-15 Den Norske Stats Oljeselskap A.S. Apparatus for the measurement of the fraction of gas in a two-component fluid flow comprising a liquid and a gas in mixture
US4733166A (en) * 1986-03-17 1988-03-22 Wagner Delmer W Apparatus for measuring the moisture content of moving materials
US4782282A (en) * 1986-07-09 1988-11-01 Dickey-John Corporation Capacitive-type seed sensor for a planter monitor
NL1005956C2 (nl) * 1997-05-02 1998-11-03 Arnold Brookhuis Textieltechni Inrichting voor het meten van de vochtigheid van een materiaal, bijvoorbeeld hout.
WO1998050785A1 (en) * 1997-05-02 1998-11-12 Arnold Brookhuis Textieltechniek B.V. Device for measuring the humidity of a material, e.g. wood
WO2005103661A1 (en) * 2004-04-22 2005-11-03 Damsten Leif Daniel Method and apparatus for measuring the moisture content of a block of timber
US20100231231A1 (en) * 2009-03-10 2010-09-16 Microtec S.R.L. Method for calibrating apparatuses for determining the moisture content of products based on capacitive measurements, and device for simulating the dielectric properties of products, such as wood, for use in this method
US8410796B2 (en) * 2009-03-10 2013-04-02 Microtec S.R.L. Method for calibrating apparatuses for determining the moisture content of products based on capacitive measurements, and device for stimulating the dielectric properties of products, such as wood, for use in this method

Also Published As

Publication number Publication date
JPS4833197B1 (enrdf_load_stackoverflow) 1973-10-12
SE331597B (enrdf_load_stackoverflow) 1971-01-04
DE1673293A1 (de) 1970-03-26
GB1117683A (en) 1968-06-19
NL6505335A (enrdf_load_stackoverflow) 1966-01-04
CH440767A (de) 1967-07-31

Similar Documents

Publication Publication Date Title
US3339137A (en) Moisture determining apparatus having adjacent electrode pairs driven outof-phase
US3774238A (en) Three-terminal capacitive apparatus for remotely responding to a condition or dielectric properties of a material
US2718620A (en) Means for measurement by electrical condenser of characteristics and conditions of material
US3515987A (en) Coplanar dielectric probe having means for minimizing capacitance from stray sources
US2428700A (en) Capacitative feed-back device for electrical testing
US3012193A (en) Apparatus and method for measuring capacitivity of a material
US3636763A (en) Measurement of the flow of particulate material
US3535631A (en) Apparatus for determining thickness variations across electrically conductive material
US3807055A (en) Method and apparatus for measuring the moisture content of wood
US3482162A (en) Method and apparatus for detecting the dry weight per unit-length increment of a moving stream of tobacco by determining the ratio of total moisture to moisture per unit volume
US4377783A (en) Moisture detector
US3523243A (en) Moisture measurement device insensitive to thickness of material under test
US3155901A (en) System for quantitatively measuring one property of dielectric material by applying input signals at two different frequencies to a capacitance probe and varying one input signal to maintain a constant ratio of output signals for the two frequencies
US3348313A (en) Device for detecting surface elevations in sheet material
SE460504B (sv) Foerfarande och anordning foer iakttagande av kvistar eller motsvarande i saagat virke
US3448381A (en) Portable non-contact moisture meter including electrodes driven 180 out of phase
US3785447A (en) Weighing device for movable conveyors
US2337352A (en) Metal detector
GB1295460A (enrdf_load_stackoverflow)
US3659194A (en) Magnetic sensor having a heat treated housing for collimating the sensor{40 s flux
GB1067459A (en) Improvements in dielectric gauges
GB625024A (en) Improvements in or relating to instruments for measuring moisture content in wool and other substances
US3491292A (en) Standard sample and method for simulating the effect of moist paper and the like on a capacitive gauge for dielectric materials
US4733166A (en) Apparatus for measuring the moisture content of moving materials
US3004216A (en) Null-indicating impedance bridge