WO2012105897A1

WO2012105897A1 - Electromagnetic monitoring unit for a liquid substance

Info

Publication number: WO2012105897A1
Application number: PCT/SE2012/050094
Authority: WO
Inventors: David Livshits
Original assignee: DeLaval Holding AB
Current assignee: DeLaval Holding AB
Priority date: 2011-02-02
Filing date: 2012-01-31
Publication date: 2012-08-09
Anticipated expiration: 2013-08-02

Abstract

A monitoring unit (100) determines an attribute (P) of a liquid substance (L) flowing (F) through a non-magnetic conduit (110). To this aim, a helical coil (125) encircles the non-magnetic conduit (110). The helical coil (125) imposes an electromagnetic field (B) on the liquid substance (L) and registers fluctuations in the electromagnetic field (B) caused by the liquid substance (L). Said fluctuations are indicative of at least one electromagnetic property (z) of the liquid substance (L), and based on the at least one electromagnetic property (z), in turn, a processor (170) derives the attribute (P). For enhanced efficiency and reduced interference, a magnetic shield (150) is arranged around the helical coil (120), which magnetic shield (150) concentrates the electromagnetic field (B) towards the non-magnetic conduit (110) inside the helical coil (125).

Description

ELECTROMAGNETIC MONITORING UNIT FOR A LIQUID SUBSTANCE

THE BACKGROUN D OF THE I NVENTION AND PRIOR ART

The present invention relates generally to automatic determination of at least one attribute of a liqu id substance. More particu- larly, the invention relates to a mon itoring unit according to the preamble of claim 1 .

In many areas, an efficient and reliable handling of liquid substances is highly important. This is especially true when producing and processing foodstuffs. Milk extraction and milk pro- cessing are here important examples. Generally, the automatic milking solutions are becoming increasingly efficient and sophisticated . Today, there is also a strong demand for flexible and animal-friendly milk production . For example, so-called milking robots have been introduced , which enable animals to autono- mously decide when they are to be milked . Milking robots are advantageous because they reduce the amount of manual labor involved in milking . Milking robots are also desirable from an animal health point-of-view, since thereby it is uncomplicated to extract milk more frequently than by applying the existing alter- native solutions, and in general , high-frequency milking vouches for a good udder health . However, milking robots may be somewhat problematic because these machines are often operated without any human operator being present. Th is, in turn , renders a safe and reliable operation high ly important. One aspect of such an operation is that problems related to unsatisfying milk quality must be resolved automatically. For example it is necessary to automatically detect unacceptably high concentrations certain constituents in the milk, such that adequate counter measures can be taken promptly. US 4,678 ,995 describes an apparatus and method for determining the presence of specific substances in a sample, e.g . of tis- sue, by nuclear magnetic resonance (NMR) and then obtaining a high-resolution N MR image of these substances.

US 7, 141 ,978 discloses a solution for analyzing fluid samples by means of an NM R probe comprising multiple NMR detection si- tes.

WO 00/39578 reveals a method and apparatus for estimation of a cell count in a body flu id . Here, a mid-I R spectrum is recorded and the spectral information therein serves as a basis for deriving a number of cells in the body fluid . This document also briefly mentions the possibility to employ NMR spectroscopy.

US 2009/0278685 describes methods and systems for calibration of radio-frequency identification (RFI D) sensors involving impedance measuring by determining a complex impedance spectrum, a phase ang le and/or a magnitude of the impedance. Inter alia, the document mentions that the RFI D sensors may be adapted to measure physical, chemical and biological parameters; each sensor can have a digital I D and be calibrated to accurately react to a parameter of interest through changes in measurements of the sensor's complex impedance. US 7,219,024 discloses a system, method and program product for determining in-place engineering properties, such as density and moisture content of certain engineering materials. A database, material model and sensor model are also shown . The document generally relates to material analysis, and to the field of impedance spectroscopy, and the determination of engineering properties of a material from the response to electromagnetic probing in a defined frequency spectrum.

US 6,51 1 ,851 reveals a method for identifying a change in the composition of a liquid . Here, a time varying electrical or elect- romagnetical input signal is applied to the liquid in a range of frequencies encompassing a resonant frequency of an electrical circuit comprising the liquid . An impedance quantity is measured of said electrical circuit by means of the output signal as a function of the frequency of the time varying input signal in said range of frequencies. A resonant frequency of said electrical circuit is determined . After a change in the composition of the liqu id , variation in the impedance quantity is measured at or near the previously determined resonant frequency of said electrical circuit. The variation in the impedance quantity is then related to the change in the composition .

WO 2008/076453 describes a flex fuel sensor, wh ich is deployed in conjunction with a fuel transfer line, or at the bottom/side of a fuel tank. A radio-frequency signal at a constant frequency may be generated across a resonant circu it, which comprises an inductor and a printed circuit board trace capacitor, capacitor plates, semi cylindrical capacitor plates, or the like. Electromagnetic radiation is propagated into the passing fuel in the transfer pipe. The conductivity and dielectric properties of the fuel change the capacitance of the trace capacitor plates. These changes are proportional to the ethanol/alcohol content of the fuel , and are preferably detected by a microcontroller, or the like, and then transmitted to a flex fuel vehicle engine management sys- tern.

PROBLEMS ASSOCIATED WITH THE PRIOR ART

Hence, diverse solutions are known for determining various properties of different kinds of entities (e.g . represented by tissue pieces, flu id samples or RFI D sensors) based on electromagne- tic analyses. However, there is yet no straightforward solution for unobtrusive online monitoring of the characteristics of liquids. Especially, the prior art lacks examples of efficient and sensitive online analysis means suitable to study flowing liquids.

SUMMARY OF THE I NVENTION

The object of the present invention is to alleviate the above problem, and thus offer an efficient solution for determining a measure representing an attribute of a flowing liquid substance, for instance in the form of a liquid food product.

According to the invention , the object is achieved by the initially described mon itoring unit, wherein the measurement means includes a non-magnetic condu it, a helical coil and a magnetic shield . The non-magnetic conduit is configured to transport a flow of the liqu id su bstance through the mon itoring unit. The helical coil encircles the non-magnetic conduit, and is configured to impose the electromagnetic field on the liquid substance and register fluctuations in the electromagnetic field caused by the liqu id substance flowing through the non-magnetic condu it. Here, it is assumed that the fluctuations in the electromagnetic field are indicative of the at least one electromagnetic property. The magnetic shield is arranged around the helical coil and is configured to concentrate the electromagnetic field towards the non-magnetic conduit inside the helical coil .

This monitoring unit is advantageous because it makes very good use of the applied electromagnetic field . In other words, a large proportion of the electromagnetic field is present inside the non-magnetic conduit. As a result, also small amounts of various constituents in the liquid substance can be registered , and small variations in the concentrations thereof can be detected . Moreover, since the electromagnetic leakage is small , the unit is also relatively insensitive to interference (i.e. undesired influence from the exterior). According to one preferred embodiment of the invention , a nonmagnetic spacer, preferably containing a fiberglass laminate, is arranged between the helical coil and the magnetic shield . Thereby, the mon itoring unit can be assembled in a straightforward manner and the completed unit becomes robust. At the sa- me time, the monitoring unit attains essentially the same properties as if a gas spacer, e.g . in the form of air, had been used .

According to another preferred embodiment of the invention , the magnetic shield includes a first screen ing structure having a general cylindrical shape and being arranged coaxially relative to the non-magnetic conduit and the helical coil. Preferably, the first screen ing structure contains nickel plated copper elements. Namely, such structures have been found to have exceptionally favorable screen ing characteristics with respect to electromagnetic energy. Consequently, the cylindrical magnetic shield creates a toroidal-shaped electromagnetic filed covering the nonmagnetic conduit and the liquid substance therein .

According to yet another preferred embodiment of the invention , the magnetic shield includes a second screening structure having a general cylindrical shape and being arranged between the helical coil and the first screen ing structure. The second structure has a labyrinth-shaped contour extending in at least one dimension in space relative to the non-magnetic condu it. I .e. the second screening structure may have a contour being labyrinth- shaped along an axis being parallel to a symmetry axis of the non-magnetic condu it, a contour being labyrinth-shaped along a circumference of the magnetic shield , or both . Naturally, the first screening structure may also be configured to have labyrinth properties analogous to those of the second screening structure described above. Namely, the labyrinth shape has been found to be especially efficient in order to trap electromagnetic energy, and thus prevent this type of energy from reaching outside of a screened volume. According to still a preferred embodiment of the invention , the helical coil includes a number of coaxially arranged cut-open ring-shaped members that are galvanically interconnected with one another via a plurality of connection pins. Specifically, a primary pin of said plurality of connection pins is arranged on a first side of a cut in a given ring-shaped member and connects the given ring-shaped member to a preced ing ring-shaped member. Corresponding ly, a secondary pin of said plurality of connection pins is arranged on a second side of the cut in the g iven ring-shaped member and connects the given ring-shaped member to a succeeding ring-shaped member, and so on . Thus, the cut-open ring-shaped members and the connection pins create a helical structure, which is suitable for implementation in a multi-layered printed circuit board with one ring-shaped member per layer. According to a further preferred embodiment of the invention , the first and second screen ing structures are likewise formed by interconnected layers of a multi-layered printed circuit board . Thereby, the entire mon itoring un it may be conven iently implemented in a multi-layered printed-circu it-board design . According to another preferred embodiment of the invention , the helical coil includes at least one copper-containing conductor. Copper is a cost-effective electric conductor. Thus, when arranged as a helical coil and run through by an alternating current, a copper conductor may produce electromagnetic fields in a highly efficient manner.

According to yet another preferred embodiment of the invention , for the similar reasons, the nickel plated conductor members of the magnetic shield contain a copper base.

According to still another preferred embod iment of the invention , the non-magnetic conduit has an inside surface layer configured to contact liquid substance, which inside surface layer contains synthetic diamonds, and for example being 15 - 25 microns thick. Namely, such a coating has been found to be entirely neutral , both with respect to chemical interaction with the exami- ned liquid substances and with respect to electromagnetic energy losses.

Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims. BRI EF DESCRI PTI ON OF TH E DRAWI NGS

The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

Figure 1 shows a schematic cross-section side view of a monitoring unit according to one embodiment of the invention;

Figure 2 shows a more detailed cross-section side view of one embodiment of the proposed helical coil and magnetic shield ;

Figure 3 illustrates how the helical coil may be formed according to one embodiment of the invention ; and

Figure 4 illustrates, schematically, how the helical coil and the magnetic shield may be arranged relative to one another according to one embodiment of the invention. DESCRI PTION OF PREFERRED EMBODI MENTS OF THE I NVENTION

Initially, we refer to Figure 1 , which shows a schematic cross- section side view of a monitoring unit 100 according to one embodiment of the invention . The monitoring unit 100 includes measurement means and a processor 1 70. The measurement means are configured to su bject a liquid substance L passing through the monitoring unit 100 to an electromagnetic field B, and under influence thereof measure at least one electromagnetic property of the liquid substance L. The measurement means, in turn , includes a nonmagnetic conduit 1 10, a helical coil 125 and a magnetic shield 150.

The non-magnetic conduit 1 10 is configured to transport a flow F of the liqu id substance L through the monitoring unit 100. Thus, the mon itoring unit 100 may be arranged on a liquid conduit, e.g . a milk line, for online study of the liquids transported there through .

The helical coil 125 encircles the non-magnetic conduit 1 10 and is configured to impose the electromagnetic field B on the liquid substance L. A signal generator 160 producing alternating current is connected to the helical coil 125, and thus causes the helical coil 125 to generate the electromagnetic field B . The helical coil 125 is also configured to register any fluctuations in the electromagnetic field B caused by the liqu id substance L flowing through the non-magnetic condu it 1 10. Here, it is assumed that the fluctuations in the electromagnetic field B are ind icative of at least one electromagnetic property z which , in turn , reflects an attribute P of the liquid substance L.

The electromagnetic field B influences the liquid substance L depending on the electromagnetic properties of the liquid substance L. This influence may be explained by linear and vortical currents of conductivity, linear and vortical currents of d isplacement (caused by d ielectric polarization) as well as linear and vortical ion ic currents occurring in the liquid substance L in response to the electromagnetic field B . According to a principle called super attitude of fields, the above-mentioned electric phenomena, in turn, bring about distortions in the electromagnetic field B. Consequently, the helical coil 125 may detect these d istortions as indications of the at least one electromagnetic pro- perty z of the liquid substance L. In practice, a resonant circuit (here symbolized by a general resistive element r and a general capacitive element c) is preferably used to determine the at least one electromagnetic property z, for instance based on a so-called resonant contour. Namely, any change in the elec- tromagnetic properties of the liquid substance L leads to changes in the resonant contour, i.e. the resonant frequencies and amplitudes of the resonant circuit in which the helical coil 1 25 is included . By comparing these changes with a statistical model, variations of the at least one electromagnetic property, such as an impedance z, may be determined . Preferably, the processor 1 70 is configured to determine the at least one electromagnetic property z (although theoretically th is deduction may be performed elsewhere, e.g . in other circu itry connected to the helical coil 1 25). I n any case, based on further statistic models, the processor 1 70 is configured to derive at least one attribute P of the liquid substance L based on the at least one electromagnetic property z. The attribute P may represent various characteristics and/or constituents of the liquid substance L, such as water content, a concentration of sodium , the total concentration of solids, pH level and electrical conductivity. Provided that the liquid substance L is milk, the attribute P may further reflect a concentration of lactose, a concentration of fat, a concentration of protein , a concentration of urea and/or a concentration of somatic cells The magnetic shield 150 is arranged around the helical coil 125. Specifically, the magnetic shield 150 is configured to concentrate the electromagnetic field B towards the non-magnetic condu it 1 10 inside the helical coil 125, so that a relatively large proportion of the electromagnetic field B is present inside the non- magnetic conduit 1 10.

According to the invention , this concentration of energy is the resu lt of the geometrical interrelations between the non-magnetic condu it 1 10, the helical coil 125 and the magnetic sh ield 150. First, all these elements 1 10, 125 and 150 have a general cy- lindrical outline. Second , the elements 1 10, 125 and 150 are arranged coaxially relative to one another in the following order inside and out: the non-magnetic condu it 1 10, the helical coil 125 and the magnetic shield 150. Namely, this configuration concentrates the intensity of the electromagnetic field B into the center of the coaxial system, wh ich also increases the energy of any reflected resonant signal and causes a high contrast between useful and parasitic signals.

Preferably, the magnetic shield 150 has an axial extension exceed ing that of the helical coil 1 25, and the magnetic sh ield 150 is positioned such that it extends outside of both ends of the helical coil 125 because this further reduces the leakage of electromagnetic energy outside of the magnetic sh ield 1 50, and thus strengthens the intensity of the electromagnetic field B inside the non-magnetic conduit 1 10. Consequently, the characteristics of the liquid substance L may be determined with high accuracy and sensitivity.

In Figure 1 , the electromagnetic field B is symbolized by field lines with a toroidal-shape around the helical coil 125, which field B is concentrated towards the non-magnetic condu it 1 1 0 inside the helical coil 125 (i.e. field B is relatively weak outside the magnetic shield 150). This is to reflect the effect of the proposed magnetic shield 150 resulting in that the electromagnetic energy B from the helical coil 125 is predominantly present in- side the magnetic sh ield 1 50.

Figure 2 shows essentially the same view of the proposed nonmagnetic condu it 1 10, the helical coil 125 and the magnetic shield 1 50 as in Figure 1 . However, Figure 2 also reveals further details according to embodiments of the invention. According to one embodiment of the invention , a non-magnetic spacer 21 0 is arranged between the helical coil 125 and the magnetic shield 1 50. Basically, the purpose of the non-magnetic spacer 210 is to ensure a desired position ing of the non-magnetic conduit 1 10, the helical coil 125 and the magnetic shield 150 relative to one another. Given that this positioning can be attained by other means, for example by adequate fitting elements in the distal ends of the helical coil 125 and the magnetic shield 150 respectively, there is no need for a rig id spacer 210. Thus, air, or any other non-magnetic gas is a conceivable alternative. Preferably, however, the non-magnetic spacer 210 contains a fiberglass laminate.

As mentioned above, it is desirable that the magnetic shield 150 has a general cylindrical shape and is arranged coaxially relati- ve to the non-magnetic conduit 1 1 0 and the helical coil 1 25. According to one preferred embodiment of the invention , the magnetic shield 150 also contains a first screening structure 151 .

Furthermore, according to another preferred embodiment of the invention, the magnetic shield 150 includes a second screening structure 152 located inside of first screening structure 151 , however outside the helical coil 125 (i.e. the second screening structure 152 is arranged between the helical coil 125 and the first screening structure 151 ). The second screening structure 152 likewise has a general cylindrical shape, and preferably, the second screening structure 152 has a labyrinth-shaped contour extending in at least one d imension in space relative to the nonmagnetic conduit 1 10.

In Figure 2 , the labyrinth-shaped contour is implemented by means of a set of conductor members 52c, 53a and 53c interconnected with one another. One or more radial conductor members 53a may also be included in the labyrinth structure, which radial conductor members 53a connect the second screening structure 152 with the first screening structure 1 51 . Preferably, the conductor members 51 c, 52c, 53a and 53c are nickel plated because nickel has especially high screening capacity with respect to magnetic energy. However, it is sufficient that the surface contains nickel. Thus, the base material of the conductor members 51 c, 52c, 53a and 53c may for example be made of copper. Further aspects of the labyrinth-shaped contour will be explained below with reference to Figure 4.

According to one embod iment of the invention , the non-magnetic conduit 1 1 0 has an inside surface layer 1 10D configured to contact the liquid substance L during passage thereof through the monitoring unit 100, which inside surface layer 1 10D contains synthetic diamonds. Preferably, the surface layer 1 10D is at least 15 microns thick. However, it is not required that the layer thickness exceeds 25 microns. Namely, such a coating has been found to be entirely neutral . This means that the coating neither interacts chemically with the examined liquid substances L nor causes any losses with respect to the electromagnetic field B.

Figure 3 illustrates how the helical coil 125 may be formed ac- cording to one embodiment of the invention . Figure 3 shows a coil with four loops. However, according to the invention, any higher or lower number of loops is equally well conceivable. The specific design of the helical coil 125 is determined by the desired properties of the electromagnetic field B. As can be seen , the proposed helical coil 125 does not have a conventional helix shape. I nstead , the coil 125 contains a number of coaxial cut-open ring-shaped members 125a, 125b and 125c that are galvanically interconnected with one another via a plurality of connection pins a and b respectively. I n Figure 3, a connection pin c represents a first connection to external circuitry (such as the signal generator 160 and the resonant circuit r and c in Figure 1 ). A connection pin d represents a second such connection in the opposite end of the helical coil 125.

Now, let us study a given ring-shaped member 125b. This mem- ber 1 25b is connected to a preced ing ring-shaped member 125a in the helical coil 125 via a primary pin a, which is arranged on a first side of a cut CT in the member 125b. A secondary pin b arranged on a second (i .e. the opposite) side of the cut CT connects the member 125b to a succeed ing ring-shaped member 125c. Each ring-shaped member (except for an initial member connected to the connection pin d and a final member 125c) is thus connected with two other ring-shaped members of the coil 125. This is an advantageous design , since it is straightforward to implement in a multi-layered printed circuit board (PCB). Na- mely, in such a design , each ring-shaped members 125a, 125b and 125c is embodied in a separate layer of the multi-layered PCB (cf. layers Ba, Bb and Be in Figure 2).

Analogously, the first and second screening structures 151 and 152 of the magnetic shield may likewise be formed by interconnecting the layers Ba, Bb and Be of the multi-layered PCB, for instance via conductor the members 51 c, 52c, 53a and 53c passing through the layers. In any case, from an electrical conductivity point-of-view it is desirable that the helical coil members 125a, 125b and 125c as well as the connection pins a, b, c and d contain a comparatively large percentage of copper.

Figure 4 illustrates how the helical coil 125 and the magnetic shield 150 may be arranged relative to one another according to one embodiment of the invention . Please note that, for illustrating purposes, neither the non-magnetic spacer 210 nor the connection pins a, b, c and d are shown in Figure 4. As is apparent from Figure 4, the magnetic shield 150 has structures 151 and 152 with labyrinth-shaped contours extending orthogonally to the labyrinth-shaped contour shown in Figure 2. I .e. in Figure 4, the labyrinth-shaped contour instead extends along the circumference of the magnetic shield 150. Naturally, accord ing to the invention , for enhanced magnetic screen ing , the labyrinth sha- pes may be combined so that these contours extend in both directions.

The term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components. However, the term does not preclude the presence or addition of one or more add itional features, integers, steps or components or groups thereof.

The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.

Claims

1 . A monitoring unit (100) for determining an attribute (P) of a liquid substance (L), the monitoring unit comprising :

measurement means (1 10, 125, 150, 160) configured to subject the liquid substance (L) to an electromagnetic field (B), and under influence thereof measure at least one electromagnetic property of the liquid substance (L), and

a processor (1 70) configured to derive said attribute (P) based on the at least one electromagnetic property (z),

characterized in that the measurement means comprises:

a non-magnetic conduit (1 1 0) configured to transport a flow (F) of the liquid substance (L) through the mon itoring un it (100),

a helical coil (125) encircling the non-magnetic conduit (1 10), the helical coil (1 25) being configured to impose the electromagnetic field (B) on the liquid substance (L) and register fluctuations in the electromagnetic field (B) caused by the liquid substance (L) flowing through the non-magnetic conduit (1 10) , the fluctuations being indicative of the at least one electromag- netic property (z), and

a magnetic shield (150) arranged around the helical coil (1 20) , the magnetic shield (150) being configured to concentrate the electromagnetic field (B) towards the non-magnetic conduit (1 10) inside the helical coil ( 125).

2. The mon itoring unit accord ing to claim 1 , comprising a non-magnetic spacer (210) arranged between the helical coil (125) and the magnetic shield (150).

3. The mon itoring unit according to claim 2, wherein the nonmagnetic spacer (210) comprises a fiberglass laminate.

4. The monitoring un it according to any one of the preced ing claims, wherein the magnetic shield (150) comprises a first screening structure (151 ) having a general cylindrical shape and being arranged coaxially relative to non-magnetic conduit (1 10) and the helical coil ( 125).

5. The monitoring unit according to claim 4, wherein the magnetic shield (150) comprises a second screening structure (152) having a general cylindrical shape and being arranged between the helical coil (125) and the first screen ing structure (151 ), the second screening structure (152) having a labyrinth-shaped contour extending in at least one dimension in space relative to the non-magnetic conduit (1 1 0).

6. The monitoring un it according to any one of the preced ing claims, wherein the helical coil (1 25) comprises a number of coaxial cut-open ring-shaped members (125a, 125b, 125c) being galvanically interconnected with one another via a plurality of connection pins (a, b, c) , a primary pin (a) of said plurality of connection pins (a, b, c) being arranged on a first side of a cut (CT) in a given ring-shaped member (125b) and connecting the given ring-shaped member (125b) to a preceding ring-shaped member ( 125a), and a secondary pin (b) of said plurality of connection pins being arranged on a second side of the cut (CT) in the given ring-shaped member (125b) and connecting the given ring-shaped member (125b) to a succeed ing ring-shaped member (125c).

7. The monitoring unit according to claim 6, wherein each of said ring-shaped members (125a, 125b, 125c) is embod ied in a separate layer (Ba, Bb, Be) of a printed circuit board .

8. The mon itoring unit according to any one of claims 5 to 7, wherein the first and second screening structures ( 151 , 1 52) are formed by interconnected layers of a multi-layered (Ba, Bb, Be) printed circuit board .

9. The monitoring un it according to any one of the preced ing claims, wherein the helical coil (125) comprises at least one copper-containing conductor (1 25a, 125b, 125c, a, b, c).

10. The monitoring unit according to any one of the preceding claims, wherein the magnetic shield (150) comprises a set of nickel plated conductor members (51c, 52c, 53a, 53c) being interconnected with one another.

11. The monitoring unit according to claim 10, wherein the nickel plated conductor members (51c, 52c, 53a, 53c) contain a copper base.

12. The monitoring unit according to any one of the preceding claims, wherein the non-magnetic conduit (110) has an inside surface layer (110D) configured to contact liquid substance (L), which inside surface layer (110D) contains synthetic diamonds.