CA2295520A1 - Device for measuring and/or representing electrical and magnetic material properties and properties directly derivable therefrom - Google Patents
Device for measuring and/or representing electrical and magnetic material properties and properties directly derivable therefrom Download PDFInfo
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- CA2295520A1 CA2295520A1 CA000000008A CA2295520A CA2295520A1 CA 2295520 A1 CA2295520 A1 CA 2295520A1 CA 000000008 A CA000000008 A CA 000000008A CA 2295520 A CA2295520 A CA 2295520A CA 2295520 A1 CA2295520 A1 CA 2295520A1
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- 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
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- 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
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/128—Microapparatus
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Abstract
The invention relates to a device for measuring and/or representing electrical and magnetic material properties or material properties directly derivable therefrom. The aim of the invention is to obtain better deep action measurement and to make it possible to adjust the surface geometry and sensitivity of the measurement to the samples to be examined. To this end, the resonators forming the applicator consist of electrically connected structures having two or more conductors which at least in the area of some of the voltage peaks or load centres of gravity which form during resonance are open towards the object to be measured. In addition, the conductor structures are arranged in such a way that a resulting superposition field of the load centres of gravity open towards the object to be measured can be approximated to a target field geometry at the interface to the object to be measured.
Description
Device for Measuring and/or Imaging of Electrical and Magnetic Material Properties as well as Deriving Properties Indirectly.
.. ,, The invention concerns a device for measuring electrical and magnetic material properties as well as deriving properties indirectly according to the overarching term of claim 1. The invention concerns a device for measuring and/or imaging of magnetic and electrical properties of materials and deriving properties indirectly according to the overarching term of claim 29.
High frequency or microwave-reflection, transmission and resonator alignments are known constructs for determining material parameters of certain samples and test objects, e.g., the dielectric constant, magnetic permeability, moisture content and density.
Transmission measurements require a relatively large investment with at least one transmitting and receiving device, are tied to specific sample geometries and measures, strongly require accessibility to the sample from two sides and consequently are only suitable for a limited set of measuring tasks. -Reflection measurements require accessibility to the sample from one side and therefore have a fundamentally larger field of application. However, there are limits specific to this method.
A known possibility of carrying out a measurement of the reflection factor and deriving the desired parameters of the material consists of inserting the sample into the end of a hollow conductor or a coaxial line. This method strongly requires that discrete samples of the material under examination are taken from time to time and are conditioned in their shape and surface constitution to match the geometric measures of the hollow conductor.
This causes the investment of time and work to determine the parameters of the material to rise enormously.
The arrangement of a pipe line partially constituted as a hollow conductor described in DE 42 11 362 A1, which analyzes the transmission and reflection signal, can be used to determine the material parameters humidity and dielectric constant of recoveratrle media, especially liquids.
Arrangements based on the resonator principle work in a similar manner. As described in PCT registration W091/12518, the sample is either entered intermittently or continuously into the resonator so that the field lines in the area of the sample boundaries run parallel and the water content is determined from their deviation, half time differential or both parameters. A disadvantage of this arrangement lies in the necessity of entering the test object directly or through a bypass into the resonator. A limit to the size and geometries of samples that can be measured results from the mandatory parallelism of the sample boundary and the field lines, whose course in turn is influenced by sample size and geometry, and from stimulation by several oscillation modes, depending on resonator size and geometry.
[Stuchly, M. A., Stuchly, S. S.: Coaxial line reflection method for measuring dielectric properties of biological substances at radiuses and microwave frequencies - a review.
IEEE Trans. Instrum. Meas. Vol. IM-29, 1980, pp. 176-183] describe how an alignment, e.g. formed by an open coaxial line placed upon the material, in which the stray field of an electromagnetic wave enters the medium from the open surface between the external and internal lines of the feeding coaxial line. Conclusions on the dielectric properties of the material can be drawn from changes in the reflection factor at the entrance of the line.
The obvious disadvantage of this arrangement lies in the small aperture of the coaxial line and, therefore. the small range of the stray field and the small interaction surface of the test object whose properties are to be determined. Due to the small interaction volume, the measurement signal depends very strongly on the surface constitution of the sample, local inhomo~~eneitv and the couple gap of the sample. Therefore. the accuraci-of measurement with such an arrangement is very limited without intensive preparation of the sample.
An elegant option for measuring the dielectric constant of sample materials _is described in EP 0657733 A2. However, the device presented in this document also has several disadvantages: The HF-resonators used are sensitive to the mechanical loads present in most applications so that a discordance may result and the measuring accuracy of the arrangement suffers. Furthermore, the stray field of solid state resonators only extends a short way into the test object of which the dielectric constant is to be determined.
Consequently, a statement on the dielectric constant can only be made for the surface of the test object but not its body. Also, this arrangement can only be set up with a relatively high mechanical investment. Further disadvantages of the procedure lie in the large measuring surface required for both resonators, sensitivity with respect to sample properties and the conditions of probe-to-specimen contact between the interaction surfaces of the two resonators.
Often non-resonating open conductor arrangements, such as microstrips, are used to determine the desired parameters of the material. These are unilaterally brought into contact with the test object and the conduction parameters damping and phase shift are used to determine material parameters. The disadvantage of this arrangement consists of the short reach of the field into the test object that is caused by the small distance between ingoing and return line. Therefore, material parameters can only be measured in the immediate vicinity of the line and a high sensitivity towards the surface constitution of the sample and the conditions of probe-to-sample contact exists, so that the range of application of this method is limited to smooth, liquid and pasty samples.
DE 19520021 Al describes another arrangement used essentially for liquids, pasty and granular substances in connection with an analytical procedure. A single line.
e.g., a parallel wire line. is directly inserted into the test object so that the object constitutes the conductor dielectric. The propa~~ation constant of the conductor or the dielectric constant are then calculated from the frequency dependency of the reflection factor or the measurable resonance minimums. The principal disadvantages of this arrangement are that the line must be introduced directly into the test object, so that no application to solid bodies without destruction is possible; the material must enclose the lines tightly without an air gap; and the resonance frequencies change so strongly depending on the material that the frequency dependency of the properties of the material must be considered.
The problem of creating a device for measuring and/or imaging of electrical, magnetic and other material properties derived indirectly, while avoiding the limitations cited above, possessing a better depth penetration and permitting within broad terms an adaptation of surface geometry and measurement accuracy to the sample under investigation, underlies the invention.
In the sense of the invention the problem is solved by a device with the characteristics of claims 1 and 32 combined with a state of the art procedure for the calculation of material parameters from the measured resonator and reflection parameters. Advantageous executions are presented in the subclaims.
The applicator used is a structure resonating in the frequency range analyzed and made of coupled single and multiple line structures of known construction, which are open at least in the range of some of the voltage peaks and charge centers in direction of the test object and are arranged so that the resulting overlay field of their charge centers approximates a given field geometry at the boundary surface of the test object as near as possible.
If such a line structure is stimulated electrically in the proximity of its resonance frequencies, then standing waves with a defined local distribution of ranges oscillating in phase and in opposition, or voltage peaks to which charge centers can be assigned, are formed on the coupled conductors. If the line is open in the area of these charge centers, another stray field portion caused by line areas oscillating in opposition to each other overlays the electromagnetic field of the of individual line sections. It is mainly concentrated in the interior space of the ingoing and return lines.
The conductor properties of the segments, such as the propagation constant and conductor impedance, due to the small expansion of the conductor-related field portion, are only affected by a very small distance between applicator and measured-sample.
However, the electrical and magnetic stray field between areas resonating in phase already results in a shift of resonator and reflection parameters, for example in displacement of the resonance frequency, the quality factor, the impedance or the reflection factor, that is capable of analysis at far greater sample distances. With a suitable applicator geometry, a weighting of both field portions can be tuned to each other in such a manner that a shift of the resonator parameters capable of analysis and dependant on the sample occurs without changing the field distribution along the conductor and therefore on the applicator surface fundamentally.
The range of stray fields emanating from opposite charge centers depends mainly on their distance and the open surfaces interacting with the sample, so that it is possible with the applicator structures claimed through a deliberate modification of this distance but with otherwise unchanged line length and sizing, e.g., by laying the line appropriately, to adjust the stray field range or measurement sensitivity and, therefore, maximum sample distance as well as the ability to penetrate into the sample material with nearly unchanged resonance parameters.
It is possible to approximate a given charge distribution near the applicator or on the surface of the test object with an appropriate laying of several lines or selection and relative positioning of the charge centers open to the test object. This approximation can be achieved all the better if finer and more numerous line segments are chosen.
In this manner a set of applicators specifically adapted to certain measurement problems or samples, with different measurement ranges, measurement sensitivities, field ranges or depths of penetration and with almost identical resonance parameters can be designed to permit the solution of complex measurement problems with the same high frequency measurement device and all derived assemblies and the same analytical algorithm.
The resonance and reflection parameters of the resonator or their alteration during the approach of the test sample up to a given distance are determined with a measuring order customary in the frequency range (reflectometer, directional coupler, phase or square detector, vector voltmeter, network calculator, swept frequency test site) using one or several frequencies. The material parameters of interest, such as the dielectric constant, magnetic permeability or moisture content, are calculated and indicated in the sample-dependant changes in resonance parameters, possibly after analog/digital transformation, with the help of a microcomputer or controller using simulation calculations, by adaptation to a suitable physical model or by interpolation from a number of reference points that are produced by comparative measurement of control samples with known properties.
Claim 2 describes a possible execution of the resonators that is characterized by the fact that the return lines of the resonating conductor or conductive surface components are arranged with the larger part of their surfaces, their edges or their envelopes on a common surface. Planar lines on the circuit board substrates, as commonly employed for reverse side metallization in high frequency technology, with or without air gap and wire or strip lines on a common conductive surface, e.g. a metal plate, metal foil or a conductively coated body, are used. The reverse side metallization or conductive surface also forms the common surface of reference. If the reverse conductor is not executed as a grid or net structure, their envelopes form the common plane of reference. The line structures can be designed in an essentially straight line or with a special curvature, preferably with a side turned towards the sample and approximately parallel to the sample surface.
To reduce coarseness-dependent surface effects on relevant samples (e.g.
ceramic assembly components, construction elements, granular substances), a sample distance as large as possible but with sufficient measurement sensitivity is desirable.
Furthermore, measurements on granular and heterogeneous substances should be carried out integrally on larger sample volumes. Only resonators with a field range as large as possible or a large distance between opposite charge centers will do justice to these requirements. A
limit is given by half the wavelength of the line segments employed that-may be maximally extended to the free space dimensions by selection of a conductor dielectric with low dielectric constant and permeability, e.g., air.
A resonator arrangement at will generally possesses a dipole component different from zero, i.e., the field components of the line segments resonating in opposition do not compensate each other completely in the far field and electromagnetic waves radiate out in particular with charge centers located far from each other. These waves are reflected from the sample boundaries and in turn interact with the applicator, so that the sample geometry of small samples in particular may cause problems with difficult to calculate effects on measurement results. While lateral sample dimensions of sufficient size usually can be selected, sample thickness is often subject to limitations (e.g. plates, walls, layering materials).
Therefore, a compensation of dipole moments is necessary with laterally extended -resonators in particular to achieve a thickness-independent measurement of material parameters. An advantageous arrangement for a compensation of the dipole moments in the sense of the invention is described in claims 3 and 4. This mainly concerns on the one hand in phase stimulated symmetrical and in opposition stimulated inverse symmetrical resonator structures whose dipole moments compensate vertically to the plane of symmetry and on the other hand radial symmetrical structures, whose dipole moments compensate each other completely for even numbers of rotational axes in their direction, and compensate increasingly better for uneven numbers of rotational axes as their number increases.
Claims ~ - 8 describe advantageous possibilities of implementation for the conductor resonators, e.g., as electrically open-circuit (2n + 1) ~./~ - or short-circuited n~./2 - lines (n, line wave length, n natural number) that are preferentially employed when charge centers with one polarity only are required. Short-circuited conductors or conductor rings are equal to a half numbered multiple of the wavelength and contain several charge centers of alternating polarity. Through line closure with defined resistences-or serial resistances the basic quality factor of resonators can be reduced according to need, so that resonance peaks broaden.
Claim 9 describes a variant in the execution using shielded lines that are weighted with electrode surfaces or bodies at the end and whose properties as lines and interaction of charge centers with the test object are completely independent of each other.
This results in a field geometry that is dependent on the electrode surface or the surface of the electrode body and is accessible using theoretical modeling and therefore allows absolute measurement without standardizations.
Claim 10 describes a possibility of tuning the input and output impedances of the resonators and the high frequency measurement devices with each other in a manner that a defined electrical adjustment or a defined coupling factors are achieved.
For this purpose adaptation networks firmly connected to the resonator and integrated into the applicator and composed of components or lines, in the simplest case parallel or serial open- or short-circuited line pieces, are employed.
Claim 11 describes resonators with only one connection point in the form of an electrical one-port network, which is relatively easy to manufacture and permits a measurement of the resonance parameters in reflection with relatively little investment.
Claim 12 describes transmission resonators with one or several resonant branches in the form of an electrical two- or multiple-port network that enable, apart from an analysis of the reflection parameters, a measurement of transmission parameters.
Claim 13 describes resonators whose external electrical field mainly runs in a plane vertically to the sample surface and therefore permits measurement of anisotropic properties through applicator rotation. _ - .:
Claim 14 describes the arrangement of at least three such anisotropic resonators in three different directions in the form of a jointly fed transmission resonator from which the anisotropic properties of the sample can be calculated from transmission parameters measured simultaneously or sequentially with a multiplexor but without applicator rotation. This is possible because the directional distribution of anisotropic sample properties within the interaction surface may be described as an ellipsis whose course through three points in different directions is described completely.
Claims 1 S and 16 describe surface shapes of the line resonators that are highly symmetrical or particularly adapted to the sample and secure a favorable field geometry for measurement depending on sample shape.
Claim 17 demonstrates a resonator-form that is particularly easy to construct and in which a continuous conductive surface, for example a metal sheet or a metallized circuit board substrate, forms the common return line of all line pieces and may also be employed at the same time in their mechanical attachment.
Claim 18 describes advantageously employable possibilities to guarantee a defined distance between the measured sample and the resonator electrodes using spacers like rings or washers or by directly setting appropriately shaped resonator areas.
Claim 19 demonstrates a possibility to elevate the coupling between sample and applicator by enlarging the coupling surfaces or reducing the distances in the charge centers. as the interaction ran~~es most important to the measurin<~ effect.
or by a combination of both options.
The applicator with a contact device described in claim 20 creates reproducible conditions for coupling to the test sample and eliminates in particular instabilities of the measurement result especially noticeable with small couple gaps or direct attachments with changing contact pressure, angling and such.
An electrical cover described in claim 21 serves to protect the applicator against mechanical damage, improves i. a. the coupling of the measurement device and prevents a penetration of liquid, pasty and granular measured substances into the line structures.
Claim 22 describes a puncture or dip applicator for measurement of solid, liquid, pasty or granular substances. Here the resonating line segments of the applicator are functionally aligned on a convex surface, e.g., on the mantle of a thin cylinder or a slender cone.
Depending on the type of line and sample, a dielectric cover that prevents the penetration of the medium into the internal line spaces, can be useful. The applicator can be fixed into holes in solid substances, depending on desired durability, by mere insertion, bracketing, gluing, plastering, bolting or hammering in, e.g., by using spreading dowels.
Claim 23 describes a special applicator form with improved coupling to rough samples or samples that are not parallel to the frontal surface of the applicator using a lightly deformed dielectric, which is applied on that side of the applicator turned towards the sample and with appropriate contact homogeneously fills in the area between the resonators) and the test object. For this liquid, plastic, meltable, thixotrophic or fine-grained materials with a dielectric constant adapted to the test object and negligible dielectric losses in a flexible covering relative to the test object may be used, e.g., in the form of a thermoplastic adhesive, a liquid-filled elastic pillow on the front side of the applicator or a spreading cover made of soft plastic to fix the applicator into the hole.
Claim ?~ describes an e:~ecution of the line pieces of the resonators. For this, depending on the desired line parameters and field distributions, nearly all known two and multiple conductor arrangements, such as planar lines on dielectric substrates with or without air gap, one and multiple-veined wire and strip lines, on ground surfaces, in slots and as slotted coaxial lines, can be considered, as will become apparent in examples of executions. Also, a combination of various of these line types as well as~
targeted continuous and phased changes of conductor dimensions and distances along the line pieces are envisioned.
Claim 25 details a special class of resonators that consist of geometrically regular and irregular edged planar line components. They may be implemented as dielectric substrates with or without air gap, as are commonly used in high frequency technology, in the form of self supporting conductive surfaces such as, for example, sheet metals, plates, nets, or dielectric bodies with conductive coating.
Claims 26 - 28 describe applicator forms suitable for measurements on non-planar samples and that consist of planar lines on a flexible dielectric substrate in combination with a planar-appearing contact device. The contact can, for example, be achieved using a spring or weighted stamp, with an elastic substrate or a hydrostatic, fluid-filled pressure distribution pad or a pressure sleeve for tube or bar-shaped samples. Other possibilities are the use of adhesive films or foils and vacuum suction by means of suction canals integrated into the applicator. With sufficient flexibility of the applicator or not too low curvature radiuses an easily reproducible sample contact is achieved.
Claims 29 - 32 describe complete measuring devices or intelligent sensor components suitable for systems, in which the measuring components according to claims 1 to 28 are combined with other assemblies required for measurement in such a manner that improvements in function or handling, simplifications in production or a reduction of the overall investment result in comparison to separate high frequency measurement devices.
According to claim 31. a hi<~h frequency measuring arrangement is combined entirely or partially with an applicator into an assembly with a whole or partial probe, while the remainder of the high frequency measurement arrangement, the microcomputer or microcontroller and the indicator device are combined into a hand-held or table-top device. In this way, extreme shortening is achieved in the particular critical direct high frequency line to the resonators and, if required, the necessary socket connection or connecting lines can be shifted to less sensitive line sections. With this the accuracy of broad-banded measurements can be increased and costly corrective calculations avoided.
The execution under claim 30, with detachable applicator, permits usage of interchangeable applicators that are tailor-made for special measurement problems on the same basic instrument. This extends its field of application significantly.
Other advantageous applications are, according to claim 31, the integration of all assemblies into a compact device or, according to claim 32, into an intelligent sensor with additional integrated interface modules for the transmission of measurement results and, if required, for the control of the measurement process through a central computer.
The invention will be explained in more detail subsequently using an example of an execution. The pertinent diagrams show:
Fig. 1 a frontal view of an applicator in the sense of the invention Fig. 2 a section through an applicator in the sense of the invention Fig. 3 a resonator in the sense of the invention Fig. 4 the schematic of a device in the sense of the invention Fig. 5 a frontal view of a compact measuring device in the sense of the invention, with the cover plate removed Fig. 6 a rear view of the compact measuring device in Fig. ~
Fig. 7 a cross-section through a puncture applicator in the sense of the invention Fig. 8 a longitudinal section through the puncture applicator in Fig. 7 Fig. l and 2 show a very simply constructed applicator 1 for measuring density in foam plates, which is set directly on the test object 2 because of the low occurring dielectric constant.
The strip line resonator 3, which forms the applicator 1 and consists of six ~,/n printed contact sheets 4 that are parallel connected in the origin and evenly spaced around the circumference, is constructed upon a conventional reverse side metallized circuit board substrate with glass fiber support.
The connection is coaxial with the internal conductor being brought in centrally with a through contact from the ground side and the external conductor firmly soldered to the ground surface. Parallel to the internal conductor is a short-circuited line to the impedance transformation, which is also soldered to the ground surface, whereby an improvement through adaptation is achieved.
While supplying the applicator in the proximity of the resonance frequency, in phase charge centers form in the central area of the circuit sheet 4, so that a sort of ring-shaped field distribution with essentially radial electrical field components is generated distributed over the entire applicator surface.
The resonator 3 is glued frontally into a metal cap that also assumes the fixation of the connection cable 6 to achieve electrical shielding and mechanical fixation.
Fig. 3 and 4 show a variant of the invention for measuring dielectric material properties of plastic materials as a complete device that is optionally hand-operated or remote-controlled with a central computer. It consists of - a strip line resonator 3 contacted with a wire and set on a dielectric substrate with reverse side metallization. It is firmly glued into a metal applicator casing together with a microwave reflectometer 7, which is firmly attached to a resonator -3 for the determination of the frequency-dependent reflection factor of the resonator 3 in the range between 2 and 3 GHz.
- a plastic plate serving as the test object 2, on which the applicator casing is directly set so that the stray field of the resonator penetrates the disc;
- a storage and display device in the form of a storage circuit 10 coupled to the microcontroller 9 and an LCD dot matrix display 11 for storage and display of calculated measurement parameters, - a foil key 12 for device control and launching the measurement as well as a serial interface 13 to connect an external control computer, which is not represented in detail.
The strip line resonator 3 is constructed as a capacitatively coupled, symmetrical double ring with a circumference of 6 cm, so that a resonance frequency near 2.5 GHz results at a dielectric constant of the strip line substrate of ca. 4. To achieve a favorable interaction distance the resonator 3 is glued into the applicator casing 5 offset by several mm.
Due to the symmetrical form the inner and outer areas of the rings are oscillating against each other and consequently, no dipole moment arises in direction of the sample, i.e., there is no radiation of microwaves.
The applicator casing 5 is connected to the remaining assemblies that are integrated into a separate hand-held instrument through a cable 14 with detachable socket connection.
Optionally local operation or control of the measurement process through a central computer is possible due to the presence of a keyboard 12 and a serial interface 13.
.. ,, The socket connection between applicator 3 and the manual device 15 permits the optional operation of different applicators 1 that are tailored for specific measurement problems, types of materials and sample geometries with the same manual device 1 S so that the range of applications is considerably extended.
Fig. 5 and 6 show a further advantageous execution variant of the invention in the form of a compact measuring device for the measurement of moisture in buildings. It consists of:
- a dual A resonator in the form of a conductor ring 17 cut from Cu sheet with Coupling slat, placed over a closed ground surface in the form of a cylindrically extended metallic applicator casing 5, - a dielectric cover plate made of glass fiber strengthened circuit board dielectric PR 4, that closes the applicator 5 casing in a moisture proof way, - a massive wall as the measured sample to which the applicator casing 5 is directly applied with 3 spacing pins 19 pressed into the casing edge, - a capacitatively coupled diode detector (not shown in detail) and a microeontroller9 with integrated analog/digital transducer that calculates a humidity index from the detector frequency as measured with a fixed frequency.
- a light emitting diode row integrated into rear casing cover as display 11 and a foil kev 12, likewise integrated into the rear side. to release the measurement.
The Cu ring structure, that was cut according to the illustration, with a circumference of the magnitude of a doubled wave length, is fixed 0.5 cm above the level milled casing bottom with two pins 21 riveted at both ends that also function simultaneously as ground contacting. This provides two symmetrical, bilaterally short-circuited full wave resonators, on which two charge centers in opposition form in the respective cross-sectionally broadened areas. The feeding of both ring halves of the resonator is likewise carried out symmetrically through Coupling slat 18, so that polarities alternating around the ring circumference arise and a complete compensation of the dipole components occur in the far field.
The operation of the resonator occurs with a fixed frequency on the flank of the resonator curve below the resonance frequency. A problem-dependent shift of the resonance parameters leads to a modification of the degree of resonator transmission to the diode detector.
The diode detector is coupled capacitatively below ring 17 near one of the charge centers with an insulated coupling pin 22 that extends through the casing bottom and can be adjusted with a screw.
The other components are placed together on the backside of the applicator casing 5 in an easy-to-hold plastic housing.
Fig. 7 and 8 show the puncture applicator with dielectric covering consisting of:
- A metallic hexagonal pipe 23 as mechanical carrier. On its six surfaces narrow strips of a conventional, conductive, bilaterally metallized circuit board substrate 24 is glued.
- The hexagonal pipe 26 is electrically connected through gluing or soldering with the external conductor of a partially inserted coaxial connection cable 2~.
The circuit board substrate 24, which forms the actual resonator, with a length of approximately 3~,/2 are short-circuited on both ends and are contacted near one-of~these short-circuits from the interior of the pipe. The electrical connection occurs with insulated wires 26 that run through the back side metallization and the hexagonal pipe 23 and connect the external metallization in a joint connection point with the internal conductor of a connection cable 25.
During feeding with the resonance frequency, charge centers with alternating polarity form on the external conductor at a distance of ~,/4 from the short-circuits and ~. /2 from each other and whose stray field comprises a rotationally nearly symmetrical interaction volume.
The entire construction is mechanically protected with a Teflon 27 cover that is slipped on. At the same time the penetration of the measured substance between the conductor strips 24 or the conductor-dependent field range is prevented, so that the distribution properties on the line are hardly changed and interaction with the sample only occurs for all practical purposes via the stray field between the charge centers and through the Teflon cover 27.
List of Reference Symbols 1. Applicator .. ,:
.. ,, The invention concerns a device for measuring electrical and magnetic material properties as well as deriving properties indirectly according to the overarching term of claim 1. The invention concerns a device for measuring and/or imaging of magnetic and electrical properties of materials and deriving properties indirectly according to the overarching term of claim 29.
High frequency or microwave-reflection, transmission and resonator alignments are known constructs for determining material parameters of certain samples and test objects, e.g., the dielectric constant, magnetic permeability, moisture content and density.
Transmission measurements require a relatively large investment with at least one transmitting and receiving device, are tied to specific sample geometries and measures, strongly require accessibility to the sample from two sides and consequently are only suitable for a limited set of measuring tasks. -Reflection measurements require accessibility to the sample from one side and therefore have a fundamentally larger field of application. However, there are limits specific to this method.
A known possibility of carrying out a measurement of the reflection factor and deriving the desired parameters of the material consists of inserting the sample into the end of a hollow conductor or a coaxial line. This method strongly requires that discrete samples of the material under examination are taken from time to time and are conditioned in their shape and surface constitution to match the geometric measures of the hollow conductor.
This causes the investment of time and work to determine the parameters of the material to rise enormously.
The arrangement of a pipe line partially constituted as a hollow conductor described in DE 42 11 362 A1, which analyzes the transmission and reflection signal, can be used to determine the material parameters humidity and dielectric constant of recoveratrle media, especially liquids.
Arrangements based on the resonator principle work in a similar manner. As described in PCT registration W091/12518, the sample is either entered intermittently or continuously into the resonator so that the field lines in the area of the sample boundaries run parallel and the water content is determined from their deviation, half time differential or both parameters. A disadvantage of this arrangement lies in the necessity of entering the test object directly or through a bypass into the resonator. A limit to the size and geometries of samples that can be measured results from the mandatory parallelism of the sample boundary and the field lines, whose course in turn is influenced by sample size and geometry, and from stimulation by several oscillation modes, depending on resonator size and geometry.
[Stuchly, M. A., Stuchly, S. S.: Coaxial line reflection method for measuring dielectric properties of biological substances at radiuses and microwave frequencies - a review.
IEEE Trans. Instrum. Meas. Vol. IM-29, 1980, pp. 176-183] describe how an alignment, e.g. formed by an open coaxial line placed upon the material, in which the stray field of an electromagnetic wave enters the medium from the open surface between the external and internal lines of the feeding coaxial line. Conclusions on the dielectric properties of the material can be drawn from changes in the reflection factor at the entrance of the line.
The obvious disadvantage of this arrangement lies in the small aperture of the coaxial line and, therefore. the small range of the stray field and the small interaction surface of the test object whose properties are to be determined. Due to the small interaction volume, the measurement signal depends very strongly on the surface constitution of the sample, local inhomo~~eneitv and the couple gap of the sample. Therefore. the accuraci-of measurement with such an arrangement is very limited without intensive preparation of the sample.
An elegant option for measuring the dielectric constant of sample materials _is described in EP 0657733 A2. However, the device presented in this document also has several disadvantages: The HF-resonators used are sensitive to the mechanical loads present in most applications so that a discordance may result and the measuring accuracy of the arrangement suffers. Furthermore, the stray field of solid state resonators only extends a short way into the test object of which the dielectric constant is to be determined.
Consequently, a statement on the dielectric constant can only be made for the surface of the test object but not its body. Also, this arrangement can only be set up with a relatively high mechanical investment. Further disadvantages of the procedure lie in the large measuring surface required for both resonators, sensitivity with respect to sample properties and the conditions of probe-to-specimen contact between the interaction surfaces of the two resonators.
Often non-resonating open conductor arrangements, such as microstrips, are used to determine the desired parameters of the material. These are unilaterally brought into contact with the test object and the conduction parameters damping and phase shift are used to determine material parameters. The disadvantage of this arrangement consists of the short reach of the field into the test object that is caused by the small distance between ingoing and return line. Therefore, material parameters can only be measured in the immediate vicinity of the line and a high sensitivity towards the surface constitution of the sample and the conditions of probe-to-sample contact exists, so that the range of application of this method is limited to smooth, liquid and pasty samples.
DE 19520021 Al describes another arrangement used essentially for liquids, pasty and granular substances in connection with an analytical procedure. A single line.
e.g., a parallel wire line. is directly inserted into the test object so that the object constitutes the conductor dielectric. The propa~~ation constant of the conductor or the dielectric constant are then calculated from the frequency dependency of the reflection factor or the measurable resonance minimums. The principal disadvantages of this arrangement are that the line must be introduced directly into the test object, so that no application to solid bodies without destruction is possible; the material must enclose the lines tightly without an air gap; and the resonance frequencies change so strongly depending on the material that the frequency dependency of the properties of the material must be considered.
The problem of creating a device for measuring and/or imaging of electrical, magnetic and other material properties derived indirectly, while avoiding the limitations cited above, possessing a better depth penetration and permitting within broad terms an adaptation of surface geometry and measurement accuracy to the sample under investigation, underlies the invention.
In the sense of the invention the problem is solved by a device with the characteristics of claims 1 and 32 combined with a state of the art procedure for the calculation of material parameters from the measured resonator and reflection parameters. Advantageous executions are presented in the subclaims.
The applicator used is a structure resonating in the frequency range analyzed and made of coupled single and multiple line structures of known construction, which are open at least in the range of some of the voltage peaks and charge centers in direction of the test object and are arranged so that the resulting overlay field of their charge centers approximates a given field geometry at the boundary surface of the test object as near as possible.
If such a line structure is stimulated electrically in the proximity of its resonance frequencies, then standing waves with a defined local distribution of ranges oscillating in phase and in opposition, or voltage peaks to which charge centers can be assigned, are formed on the coupled conductors. If the line is open in the area of these charge centers, another stray field portion caused by line areas oscillating in opposition to each other overlays the electromagnetic field of the of individual line sections. It is mainly concentrated in the interior space of the ingoing and return lines.
The conductor properties of the segments, such as the propagation constant and conductor impedance, due to the small expansion of the conductor-related field portion, are only affected by a very small distance between applicator and measured-sample.
However, the electrical and magnetic stray field between areas resonating in phase already results in a shift of resonator and reflection parameters, for example in displacement of the resonance frequency, the quality factor, the impedance or the reflection factor, that is capable of analysis at far greater sample distances. With a suitable applicator geometry, a weighting of both field portions can be tuned to each other in such a manner that a shift of the resonator parameters capable of analysis and dependant on the sample occurs without changing the field distribution along the conductor and therefore on the applicator surface fundamentally.
The range of stray fields emanating from opposite charge centers depends mainly on their distance and the open surfaces interacting with the sample, so that it is possible with the applicator structures claimed through a deliberate modification of this distance but with otherwise unchanged line length and sizing, e.g., by laying the line appropriately, to adjust the stray field range or measurement sensitivity and, therefore, maximum sample distance as well as the ability to penetrate into the sample material with nearly unchanged resonance parameters.
It is possible to approximate a given charge distribution near the applicator or on the surface of the test object with an appropriate laying of several lines or selection and relative positioning of the charge centers open to the test object. This approximation can be achieved all the better if finer and more numerous line segments are chosen.
In this manner a set of applicators specifically adapted to certain measurement problems or samples, with different measurement ranges, measurement sensitivities, field ranges or depths of penetration and with almost identical resonance parameters can be designed to permit the solution of complex measurement problems with the same high frequency measurement device and all derived assemblies and the same analytical algorithm.
The resonance and reflection parameters of the resonator or their alteration during the approach of the test sample up to a given distance are determined with a measuring order customary in the frequency range (reflectometer, directional coupler, phase or square detector, vector voltmeter, network calculator, swept frequency test site) using one or several frequencies. The material parameters of interest, such as the dielectric constant, magnetic permeability or moisture content, are calculated and indicated in the sample-dependant changes in resonance parameters, possibly after analog/digital transformation, with the help of a microcomputer or controller using simulation calculations, by adaptation to a suitable physical model or by interpolation from a number of reference points that are produced by comparative measurement of control samples with known properties.
Claim 2 describes a possible execution of the resonators that is characterized by the fact that the return lines of the resonating conductor or conductive surface components are arranged with the larger part of their surfaces, their edges or their envelopes on a common surface. Planar lines on the circuit board substrates, as commonly employed for reverse side metallization in high frequency technology, with or without air gap and wire or strip lines on a common conductive surface, e.g. a metal plate, metal foil or a conductively coated body, are used. The reverse side metallization or conductive surface also forms the common surface of reference. If the reverse conductor is not executed as a grid or net structure, their envelopes form the common plane of reference. The line structures can be designed in an essentially straight line or with a special curvature, preferably with a side turned towards the sample and approximately parallel to the sample surface.
To reduce coarseness-dependent surface effects on relevant samples (e.g.
ceramic assembly components, construction elements, granular substances), a sample distance as large as possible but with sufficient measurement sensitivity is desirable.
Furthermore, measurements on granular and heterogeneous substances should be carried out integrally on larger sample volumes. Only resonators with a field range as large as possible or a large distance between opposite charge centers will do justice to these requirements. A
limit is given by half the wavelength of the line segments employed that-may be maximally extended to the free space dimensions by selection of a conductor dielectric with low dielectric constant and permeability, e.g., air.
A resonator arrangement at will generally possesses a dipole component different from zero, i.e., the field components of the line segments resonating in opposition do not compensate each other completely in the far field and electromagnetic waves radiate out in particular with charge centers located far from each other. These waves are reflected from the sample boundaries and in turn interact with the applicator, so that the sample geometry of small samples in particular may cause problems with difficult to calculate effects on measurement results. While lateral sample dimensions of sufficient size usually can be selected, sample thickness is often subject to limitations (e.g. plates, walls, layering materials).
Therefore, a compensation of dipole moments is necessary with laterally extended -resonators in particular to achieve a thickness-independent measurement of material parameters. An advantageous arrangement for a compensation of the dipole moments in the sense of the invention is described in claims 3 and 4. This mainly concerns on the one hand in phase stimulated symmetrical and in opposition stimulated inverse symmetrical resonator structures whose dipole moments compensate vertically to the plane of symmetry and on the other hand radial symmetrical structures, whose dipole moments compensate each other completely for even numbers of rotational axes in their direction, and compensate increasingly better for uneven numbers of rotational axes as their number increases.
Claims ~ - 8 describe advantageous possibilities of implementation for the conductor resonators, e.g., as electrically open-circuit (2n + 1) ~./~ - or short-circuited n~./2 - lines (n, line wave length, n natural number) that are preferentially employed when charge centers with one polarity only are required. Short-circuited conductors or conductor rings are equal to a half numbered multiple of the wavelength and contain several charge centers of alternating polarity. Through line closure with defined resistences-or serial resistances the basic quality factor of resonators can be reduced according to need, so that resonance peaks broaden.
Claim 9 describes a variant in the execution using shielded lines that are weighted with electrode surfaces or bodies at the end and whose properties as lines and interaction of charge centers with the test object are completely independent of each other.
This results in a field geometry that is dependent on the electrode surface or the surface of the electrode body and is accessible using theoretical modeling and therefore allows absolute measurement without standardizations.
Claim 10 describes a possibility of tuning the input and output impedances of the resonators and the high frequency measurement devices with each other in a manner that a defined electrical adjustment or a defined coupling factors are achieved.
For this purpose adaptation networks firmly connected to the resonator and integrated into the applicator and composed of components or lines, in the simplest case parallel or serial open- or short-circuited line pieces, are employed.
Claim 11 describes resonators with only one connection point in the form of an electrical one-port network, which is relatively easy to manufacture and permits a measurement of the resonance parameters in reflection with relatively little investment.
Claim 12 describes transmission resonators with one or several resonant branches in the form of an electrical two- or multiple-port network that enable, apart from an analysis of the reflection parameters, a measurement of transmission parameters.
Claim 13 describes resonators whose external electrical field mainly runs in a plane vertically to the sample surface and therefore permits measurement of anisotropic properties through applicator rotation. _ - .:
Claim 14 describes the arrangement of at least three such anisotropic resonators in three different directions in the form of a jointly fed transmission resonator from which the anisotropic properties of the sample can be calculated from transmission parameters measured simultaneously or sequentially with a multiplexor but without applicator rotation. This is possible because the directional distribution of anisotropic sample properties within the interaction surface may be described as an ellipsis whose course through three points in different directions is described completely.
Claims 1 S and 16 describe surface shapes of the line resonators that are highly symmetrical or particularly adapted to the sample and secure a favorable field geometry for measurement depending on sample shape.
Claim 17 demonstrates a resonator-form that is particularly easy to construct and in which a continuous conductive surface, for example a metal sheet or a metallized circuit board substrate, forms the common return line of all line pieces and may also be employed at the same time in their mechanical attachment.
Claim 18 describes advantageously employable possibilities to guarantee a defined distance between the measured sample and the resonator electrodes using spacers like rings or washers or by directly setting appropriately shaped resonator areas.
Claim 19 demonstrates a possibility to elevate the coupling between sample and applicator by enlarging the coupling surfaces or reducing the distances in the charge centers. as the interaction ran~~es most important to the measurin<~ effect.
or by a combination of both options.
The applicator with a contact device described in claim 20 creates reproducible conditions for coupling to the test sample and eliminates in particular instabilities of the measurement result especially noticeable with small couple gaps or direct attachments with changing contact pressure, angling and such.
An electrical cover described in claim 21 serves to protect the applicator against mechanical damage, improves i. a. the coupling of the measurement device and prevents a penetration of liquid, pasty and granular measured substances into the line structures.
Claim 22 describes a puncture or dip applicator for measurement of solid, liquid, pasty or granular substances. Here the resonating line segments of the applicator are functionally aligned on a convex surface, e.g., on the mantle of a thin cylinder or a slender cone.
Depending on the type of line and sample, a dielectric cover that prevents the penetration of the medium into the internal line spaces, can be useful. The applicator can be fixed into holes in solid substances, depending on desired durability, by mere insertion, bracketing, gluing, plastering, bolting or hammering in, e.g., by using spreading dowels.
Claim 23 describes a special applicator form with improved coupling to rough samples or samples that are not parallel to the frontal surface of the applicator using a lightly deformed dielectric, which is applied on that side of the applicator turned towards the sample and with appropriate contact homogeneously fills in the area between the resonators) and the test object. For this liquid, plastic, meltable, thixotrophic or fine-grained materials with a dielectric constant adapted to the test object and negligible dielectric losses in a flexible covering relative to the test object may be used, e.g., in the form of a thermoplastic adhesive, a liquid-filled elastic pillow on the front side of the applicator or a spreading cover made of soft plastic to fix the applicator into the hole.
Claim ?~ describes an e:~ecution of the line pieces of the resonators. For this, depending on the desired line parameters and field distributions, nearly all known two and multiple conductor arrangements, such as planar lines on dielectric substrates with or without air gap, one and multiple-veined wire and strip lines, on ground surfaces, in slots and as slotted coaxial lines, can be considered, as will become apparent in examples of executions. Also, a combination of various of these line types as well as~
targeted continuous and phased changes of conductor dimensions and distances along the line pieces are envisioned.
Claim 25 details a special class of resonators that consist of geometrically regular and irregular edged planar line components. They may be implemented as dielectric substrates with or without air gap, as are commonly used in high frequency technology, in the form of self supporting conductive surfaces such as, for example, sheet metals, plates, nets, or dielectric bodies with conductive coating.
Claims 26 - 28 describe applicator forms suitable for measurements on non-planar samples and that consist of planar lines on a flexible dielectric substrate in combination with a planar-appearing contact device. The contact can, for example, be achieved using a spring or weighted stamp, with an elastic substrate or a hydrostatic, fluid-filled pressure distribution pad or a pressure sleeve for tube or bar-shaped samples. Other possibilities are the use of adhesive films or foils and vacuum suction by means of suction canals integrated into the applicator. With sufficient flexibility of the applicator or not too low curvature radiuses an easily reproducible sample contact is achieved.
Claims 29 - 32 describe complete measuring devices or intelligent sensor components suitable for systems, in which the measuring components according to claims 1 to 28 are combined with other assemblies required for measurement in such a manner that improvements in function or handling, simplifications in production or a reduction of the overall investment result in comparison to separate high frequency measurement devices.
According to claim 31. a hi<~h frequency measuring arrangement is combined entirely or partially with an applicator into an assembly with a whole or partial probe, while the remainder of the high frequency measurement arrangement, the microcomputer or microcontroller and the indicator device are combined into a hand-held or table-top device. In this way, extreme shortening is achieved in the particular critical direct high frequency line to the resonators and, if required, the necessary socket connection or connecting lines can be shifted to less sensitive line sections. With this the accuracy of broad-banded measurements can be increased and costly corrective calculations avoided.
The execution under claim 30, with detachable applicator, permits usage of interchangeable applicators that are tailor-made for special measurement problems on the same basic instrument. This extends its field of application significantly.
Other advantageous applications are, according to claim 31, the integration of all assemblies into a compact device or, according to claim 32, into an intelligent sensor with additional integrated interface modules for the transmission of measurement results and, if required, for the control of the measurement process through a central computer.
The invention will be explained in more detail subsequently using an example of an execution. The pertinent diagrams show:
Fig. 1 a frontal view of an applicator in the sense of the invention Fig. 2 a section through an applicator in the sense of the invention Fig. 3 a resonator in the sense of the invention Fig. 4 the schematic of a device in the sense of the invention Fig. 5 a frontal view of a compact measuring device in the sense of the invention, with the cover plate removed Fig. 6 a rear view of the compact measuring device in Fig. ~
Fig. 7 a cross-section through a puncture applicator in the sense of the invention Fig. 8 a longitudinal section through the puncture applicator in Fig. 7 Fig. l and 2 show a very simply constructed applicator 1 for measuring density in foam plates, which is set directly on the test object 2 because of the low occurring dielectric constant.
The strip line resonator 3, which forms the applicator 1 and consists of six ~,/n printed contact sheets 4 that are parallel connected in the origin and evenly spaced around the circumference, is constructed upon a conventional reverse side metallized circuit board substrate with glass fiber support.
The connection is coaxial with the internal conductor being brought in centrally with a through contact from the ground side and the external conductor firmly soldered to the ground surface. Parallel to the internal conductor is a short-circuited line to the impedance transformation, which is also soldered to the ground surface, whereby an improvement through adaptation is achieved.
While supplying the applicator in the proximity of the resonance frequency, in phase charge centers form in the central area of the circuit sheet 4, so that a sort of ring-shaped field distribution with essentially radial electrical field components is generated distributed over the entire applicator surface.
The resonator 3 is glued frontally into a metal cap that also assumes the fixation of the connection cable 6 to achieve electrical shielding and mechanical fixation.
Fig. 3 and 4 show a variant of the invention for measuring dielectric material properties of plastic materials as a complete device that is optionally hand-operated or remote-controlled with a central computer. It consists of - a strip line resonator 3 contacted with a wire and set on a dielectric substrate with reverse side metallization. It is firmly glued into a metal applicator casing together with a microwave reflectometer 7, which is firmly attached to a resonator -3 for the determination of the frequency-dependent reflection factor of the resonator 3 in the range between 2 and 3 GHz.
- a plastic plate serving as the test object 2, on which the applicator casing is directly set so that the stray field of the resonator penetrates the disc;
- a storage and display device in the form of a storage circuit 10 coupled to the microcontroller 9 and an LCD dot matrix display 11 for storage and display of calculated measurement parameters, - a foil key 12 for device control and launching the measurement as well as a serial interface 13 to connect an external control computer, which is not represented in detail.
The strip line resonator 3 is constructed as a capacitatively coupled, symmetrical double ring with a circumference of 6 cm, so that a resonance frequency near 2.5 GHz results at a dielectric constant of the strip line substrate of ca. 4. To achieve a favorable interaction distance the resonator 3 is glued into the applicator casing 5 offset by several mm.
Due to the symmetrical form the inner and outer areas of the rings are oscillating against each other and consequently, no dipole moment arises in direction of the sample, i.e., there is no radiation of microwaves.
The applicator casing 5 is connected to the remaining assemblies that are integrated into a separate hand-held instrument through a cable 14 with detachable socket connection.
Optionally local operation or control of the measurement process through a central computer is possible due to the presence of a keyboard 12 and a serial interface 13.
.. ,, The socket connection between applicator 3 and the manual device 15 permits the optional operation of different applicators 1 that are tailored for specific measurement problems, types of materials and sample geometries with the same manual device 1 S so that the range of applications is considerably extended.
Fig. 5 and 6 show a further advantageous execution variant of the invention in the form of a compact measuring device for the measurement of moisture in buildings. It consists of:
- a dual A resonator in the form of a conductor ring 17 cut from Cu sheet with Coupling slat, placed over a closed ground surface in the form of a cylindrically extended metallic applicator casing 5, - a dielectric cover plate made of glass fiber strengthened circuit board dielectric PR 4, that closes the applicator 5 casing in a moisture proof way, - a massive wall as the measured sample to which the applicator casing 5 is directly applied with 3 spacing pins 19 pressed into the casing edge, - a capacitatively coupled diode detector (not shown in detail) and a microeontroller9 with integrated analog/digital transducer that calculates a humidity index from the detector frequency as measured with a fixed frequency.
- a light emitting diode row integrated into rear casing cover as display 11 and a foil kev 12, likewise integrated into the rear side. to release the measurement.
The Cu ring structure, that was cut according to the illustration, with a circumference of the magnitude of a doubled wave length, is fixed 0.5 cm above the level milled casing bottom with two pins 21 riveted at both ends that also function simultaneously as ground contacting. This provides two symmetrical, bilaterally short-circuited full wave resonators, on which two charge centers in opposition form in the respective cross-sectionally broadened areas. The feeding of both ring halves of the resonator is likewise carried out symmetrically through Coupling slat 18, so that polarities alternating around the ring circumference arise and a complete compensation of the dipole components occur in the far field.
The operation of the resonator occurs with a fixed frequency on the flank of the resonator curve below the resonance frequency. A problem-dependent shift of the resonance parameters leads to a modification of the degree of resonator transmission to the diode detector.
The diode detector is coupled capacitatively below ring 17 near one of the charge centers with an insulated coupling pin 22 that extends through the casing bottom and can be adjusted with a screw.
The other components are placed together on the backside of the applicator casing 5 in an easy-to-hold plastic housing.
Fig. 7 and 8 show the puncture applicator with dielectric covering consisting of:
- A metallic hexagonal pipe 23 as mechanical carrier. On its six surfaces narrow strips of a conventional, conductive, bilaterally metallized circuit board substrate 24 is glued.
- The hexagonal pipe 26 is electrically connected through gluing or soldering with the external conductor of a partially inserted coaxial connection cable 2~.
The circuit board substrate 24, which forms the actual resonator, with a length of approximately 3~,/2 are short-circuited on both ends and are contacted near one-of~these short-circuits from the interior of the pipe. The electrical connection occurs with insulated wires 26 that run through the back side metallization and the hexagonal pipe 23 and connect the external metallization in a joint connection point with the internal conductor of a connection cable 25.
During feeding with the resonance frequency, charge centers with alternating polarity form on the external conductor at a distance of ~,/4 from the short-circuits and ~. /2 from each other and whose stray field comprises a rotationally nearly symmetrical interaction volume.
The entire construction is mechanically protected with a Teflon 27 cover that is slipped on. At the same time the penetration of the measured substance between the conductor strips 24 or the conductor-dependent field range is prevented, so that the distribution properties on the line are hardly changed and interaction with the sample only occurs for all practical purposes via the stray field between the charge centers and through the Teflon cover 27.
List of Reference Symbols 1. Applicator .. ,:
2. Test object 3. Resonator 4. Conductor path sheet 5. Metal cap, applicator casing 6. Connection cable 7. Reflectometer 9. Microcontroller 10. Storage circuit 11. Display 12. Foil keyboard 13. Serial interface 14. Cable 15. Handheld device 17. Conductor ring 18. Coupling slat 19. Spacer pin 20. Ground plate 21. Riveted pin 22. Coupling pin 23. Hexagonal pipe 24. Metallized circuit board substrate 25. Connection cable 26. Vvire 27. Teflon cover
Claims (32)
1. Device for measuring electrical, magnetic and derived material properties by means of high frequency electromagnetic oscillations, consisting of one or several line or planar structures resonating electrically in the utilized frequency range -called resonators subsequently - and into whose outer electromagnetic field a measurement object can be introduced, that form together with a mechanical holding device or casing an assembly unit - called an applicator subsequently - and that are connected individually or collectively with one or several electrical connection points, characterized by:
- the resonators (3) that constitute the applicator (1) consist of electrically coupled two or multiple conductor structures, which are open towards the test object (2) in the range of several of the voltage peaks that are formed by the resonance and are associated with charge centers;
- a stray field emanating from the voltage peaks or charge centers that lies at least in part within the test object (2); and - the line structures are aligned so that a resulting overlay field of the voltage peaks or charge centers open to the test object (2) can approximate a desirable field geometry at the boundary surface to the test object (2).
- the resonators (3) that constitute the applicator (1) consist of electrically coupled two or multiple conductor structures, which are open towards the test object (2) in the range of several of the voltage peaks that are formed by the resonance and are associated with charge centers;
- a stray field emanating from the voltage peaks or charge centers that lies at least in part within the test object (2); and - the line structures are aligned so that a resulting overlay field of the voltage peaks or charge centers open to the test object (2) can approximate a desirable field geometry at the boundary surface to the test object (2).
2. Device according to claim 1, characterized by return lines of the line or planar components belonging to the resonators (3) are arranged with most of their surface components, their margins and their covers on a common surface.
3. Device according to claim 1 or 2, characterized by the line and planar components that belong to a resonator (3) and are open to the test object (2), with the exception of the electrical connection points, are arranged symmetrically to a symmetrical plane and fed electrically in phase, or are inverse symmetrical to a plane of symmetry and fed electrically in opposition.
4. Device according to claims 1 or 2, characterized by the line and planar components that belong to a resonator (3) and are open to the test object (2), with the exception of the electrical connection points, are arranged in radial symmetry, with reference to rotational axis numbering n and the natural number n = 2, ...., 120, oriented towards the test object (2) and connected electrically parallel.
5. Device according to one of the previous claims, characterized by two or multiple line structures, which constitute the resonator (3), are electrically open-circuited at the line ends.
6. Device according to one of the previous claims, characterized by two or multiple line structures, which constitute the resonator (3), are electrically short-circuited at the line ends.
7. Device according to one of the previous claims, characterized by two or multiple line, which constitute the resonator (3), are electrically closed with defined resistances at their ends.
8. Device according to one of the previous claims, characterized by two or multiple line structures, which constitute the resonator (3), are connected to their supply points through serial serial resistances of defined size.
9. Device according to one of the previous claims, characterized by two or multiple line structures, which constitute the resonator (3), are electro-magnetically shielded and only connected to an electrode body open to the test object (2) or a conductive electrode surface at their line ends.
10. Device according to one of the previous claims, characterized by one or several impedance transformation connections that are located between the resonators (3) and the electrical connection points leading to the outside and that these impedance transformation connections are firmly connected to the resonators (3) and integrated constructionally into the applicator (1).
11. Device according to one of the previous claims, characterized by the resonators (3) having only one connection point of the electrical one-portal connection type.
12. Device according to one of the previous claims, characterized by the resonators (3) having only two or more connection points of the electrical two or multiple portal connection type.
13. Device according to one of the previous claims, characterized by charge centers of a resonator (3) that lie in a plane vertical to the sample surface.
14. Device according to claim 13, characterized by at least three transmission resonators (3) that are executed according to the characterizing part of claim 3 and lie in different directions have a common connection point and that their respective second connection point are separate or lead outside via a multiplexor that can be switched from the outside.
15. Device according to one of the previous claims, characterized by the line and conductive surface components, which belong to a resonator (3), being arranged with most of their surface or their edges on a ball, cone, cylinder, ellipsoidal, prism, pyramidal or plane surface.
16. Device according to one of the previous claims, characterized by the line and conductive surface components, which belong to a resonator (3), being arranged with most of their surface or their edges on a surface parallel to the surface of the test object.
17. Device according to one of the previous claims, characterized by a common conductive surface that forms the return line of all line and conductive surface components that belong to one resonator (3).
18. Device according to one of the previous claims, characterized by the applicator (1) bearing on the side turned towards the test object (2) object-specific contact points, surfaces or other spacing bodies (19), that guarantee a defined distance between the resonator(s) and the test object, or that part of the resonator surface itself serves as the contact surface.
19. Device according to one of the previous claims, characterized by the line surfaces of the resonators (3) turned towards the test object (2) being enlarged in the charge centers compared to other line cross-sections and/or placed particularly close to the test object (2).
20. Device according to one of the previous claims, characterized by the resonators (3) placed against a point or area of the test object (2) by means of a contact device of generally familiar construction.
21. Device according to one of the previous claims, characterized by the applicator (1) being covered entirely or partially by a dielectric coating, covering or cover on the side that is turned towards the test object (2).
22. Device according to one of the previous claims, characterized by the applicator (1) being dipped, embedded, glued, screwed, tapped or bracketed directly or in its cover into test objects (2) of solid, liquid, pasty and granular consistency.
23. Device according to one of the previous claims, characterized by a deformable dielectric being applied to the side of the applicator (1), which is turned towards the sample, and fills the space between the resonator(s) and the test object homogeneously in the measuring area.
24. Device according to one of the previous claims, characterized by the line and conductive surface elements of the resonator(s) being constituted as microstrip-, suspended substrate, slotted line, co-planar line technology, as symmetrical or asymmetrical wire or strip lines over the planar extended reverse side electrode or as slotted coaxial conductors.
25. Device according to one of the previous claims, characterized by the line-and conductive surface elements of the resonator(s) being executed as geometrically regular or irregular edged surface components in microstrip, suspended substrate technology or with air as the dielectric.
26. Device according to one of the previous claims, characterized by the resonator(s) (3) being formed as planar lines and pressed with a suitable contact device of generally known construction flat against the test object.
27. Device according to one of the previous claims, characterized by the resonator(s) (3) being formed as planar lines on a flexible substrate and having an adhesive film or a sticky foil on the side turned towards the sample for direct adhesion to the test object.
28. Device according to one of the previous claims, characterized by the resonator(s) (3) being formed as planar lines on a flexible substrate and being provided on their back side with suction channels that end in a connecting piece for vacuum fixation on the test object.
29. Device for measuring electrical, magnetic derived material properties, according to the overarching term of claim 1, in which the test object can be entered into the area of the electromagnetic external field of the applicator; also consisting of a high frequency measurement device linked to the externally accessible electrical connection points for determining electrical resonance parameters of individual resonators and/or the transmission route between each of two resonators at one or several frequencies between 10MHz and 1 THz; a microcomputer or microcontroller that calculates the pertinent material parameters from the resonance parameters according to familiar mathematical algorithms; if necessary a grid device to realize a lateral relational movement between the applicator and the test object and a storage and display device for storing and displaying the calculated material parameters, if required in relationship to lateral measuring position in the form of a figure, a curve or a planar representation and an operating device to control the instruments and initiate the measurement, characterized by the high frequency measurement device being entirely or partially combined with the applicator (1) into a compact assembly in the form of a probe, while the remaining components of the high frequency measuring alignment, the microcomputer or controller (9), the storage (10), display (11) and operating device (12) are combined in a casing as a hand-held (15) or table-top device.
30. Device according to claim 29, characterized by the applicator (1), together with part of the high frequency measurement device being executed in a separate assembly in the form of a probe or a probe part and possessing detachable mechanical and electrical connections to the other components of the device.
31. Device according to claim 29, characterized by the applicator (1) and all other device components being mechanically integrated into the casing as a compact instrument.
32. Device according to claim 29, characterized by the applicator (1), the high frequency measuring device, the microcomputer or controller (9) and, if required, the additional interface assembly being integrated mechanically into the casing as an intelligent sensor, while the storage (10), display (11), and operating device (12) are entirely or partially set apart in a control computer, which is coupled to the intelligent sensor with a cable, infrared, wireless, telephone, light, sound or another connection.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19729730.7 | 1997-07-11 | ||
| DE19729730A DE19729730C1 (en) | 1997-07-11 | 1997-07-11 | Device for measuring and / or imaging electrical, magnetic and material properties derived indirectly therefrom |
| PCT/DE1998/001930 WO1999002979A2 (en) | 1997-07-11 | 1998-07-10 | Device for measuring and/or representing electrical and magnetic material properties and properties directly derivable therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2295520A1 true CA2295520A1 (en) | 1999-01-21 |
Family
ID=7835387
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000000008A Abandoned CA2295520A1 (en) | 1997-07-11 | 1998-07-10 | Device for measuring and/or representing electrical and magnetic material properties and properties directly derivable therefrom |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0995109A2 (en) |
| JP (1) | JP2001509599A (en) |
| AU (1) | AU9336898A (en) |
| CA (1) | CA2295520A1 (en) |
| DE (1) | DE19729730C1 (en) |
| WO (1) | WO1999002979A2 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19925468A1 (en) | 1999-06-03 | 2000-12-07 | Hauni Maschinenbau Ag | Stray field probe |
| EP1437588B1 (en) * | 2003-01-10 | 2005-08-31 | AMS- Advanced Microwave Systems GmbH | Microwave stray field sensor |
| US7151380B2 (en) * | 2004-08-06 | 2006-12-19 | Voith Paper Patent Gmbh | Microwave water weight sensor and process |
| DE102004055797B4 (en) * | 2004-11-18 | 2011-12-29 | Arndt Göller | Method and device for detecting the internal structure of non-metallic objects |
| DE102005039851B4 (en) * | 2005-08-23 | 2020-01-16 | Continental Automotive Gmbh | humidity sensor |
| DE102006036188B4 (en) * | 2006-08-01 | 2011-06-16 | Franz Ludwig Gesellschaft für Mess- und Regeltechnik mbH | Resonant microwave sensor |
| PL211294B1 (en) * | 2008-06-16 | 2012-05-31 | Lubelska Polt | Probe for measuring moisture, preferably in elements with curved surfaces |
| DE102011084954A1 (en) * | 2011-10-21 | 2013-04-25 | BSH Bosch und Siemens Hausgeräte GmbH | Dishwasher for domestic use, has program control device to control drying passage so that door is opened at end or during drying passage while opening parameter is defined as function of user preference/environmental condition |
| FR3026186B1 (en) * | 2014-09-19 | 2016-12-09 | Saint-Gobain Centre De Rech Et D'Etudes Europeen | NON-DESTRUCTIVE CONTROL METHOD |
| DE102017006187A1 (en) | 2017-06-30 | 2019-01-03 | Ralf Moos | Method for detecting a gas concentration |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4004119A1 (en) * | 1990-02-10 | 1991-08-14 | Tews Elektronik Dipl Ing Manfr | METHOD FOR MEASURING THE HUMIDITY OF A MEASUREMENT WITH THE AID OF MICROWAVES AND DEVICE FOR IMPLEMENTING THE METHOD |
| DE4211362C2 (en) * | 1992-04-04 | 1995-04-20 | Berthold Lab Prof Dr | Device for determining material parameters by microwave measurements |
| DE4342505C1 (en) * | 1993-12-08 | 1995-04-27 | Stange Gerd | Method and device for measuring the dielectric constant of sample materials |
| DE19520021A1 (en) * | 1995-05-31 | 1996-12-05 | Umwelt Geraete Technik Gmbh | Determining dielectric constants in mixture e.g. in arable soil or in liquid |
-
1997
- 1997-07-11 DE DE19729730A patent/DE19729730C1/en not_active Expired - Lifetime
-
1998
- 1998-07-10 AU AU93368/98A patent/AU9336898A/en not_active Abandoned
- 1998-07-10 CA CA000000008A patent/CA2295520A1/en not_active Abandoned
- 1998-07-10 WO PCT/DE1998/001930 patent/WO1999002979A2/en not_active Application Discontinuation
- 1998-07-10 EP EP98946230A patent/EP0995109A2/en not_active Ceased
- 1998-07-10 JP JP2000502410A patent/JP2001509599A/en not_active Withdrawn
Also Published As
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|---|---|
| EP0995109A2 (en) | 2000-04-26 |
| JP2001509599A (en) | 2001-07-24 |
| AU9336898A (en) | 1999-02-08 |
| WO1999002979A3 (en) | 1999-09-10 |
| DE19729730C1 (en) | 1999-04-22 |
| WO1999002979A2 (en) | 1999-01-21 |
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