Transmission Line Probes

Abstract

The invention relates to a transmission line probe. The invention relates to a transmission line probe (18) for use in a radar level gauge system (10) configured to determine the filling level (L) and density of a product (14) contained in a container (12), wherein the transmission line probe comprises: at least one probe wire (24a, 24b) adapted to direct an electromagnetic emission signal (S) towards the product T ) and guide the electromagnetic emission signal (S T ) at least partially through the product, and directing the electromagnetic return signal (S R ) returned from a surface (22) or interface of the product; and a plurality of insulating dielectric beads (26, 26') arranged along at least one probe line and configured to reduce electromagnetic signal attenuation caused by the product. The invention also relates to a radar level gauge system comprising such a transmission line probe and to a corresponding method.

Description

Technical Field

[0001] The present invention relates to a transmission line probe for a radar level gauge (RLG) system. The invention also relates to a radar level gauge system comprising such a transmission line probe and to a corresponding method. Background Art

[0002] It is known to use guided wave radar (GWR) in solids level applications. For example, a Rosemount 5303 transmitter with a flexible single-lead probe can be used, and measurements are taken where the probe contacts the material. This material could be, for example, plastic, fly ash, cement, sand, (cement) grain, etc.

[0003] Many types of cereal grain, such as rice, corn, and wheat, are widely stored and transported. However, in order to measure the total amount with sufficient accuracy, both the volume (e.g., in a large silo, as exemplified by level measurement in the previous paragraph) and the moisture content must be known. Each different type of grain has a so-called standard bushel weight at a specific moisture content, so the mass of the grain contained in the silo can be determined based on the volume and moisture content. Summary of the Invention

[0004] The object of the present invention is to provide an improved radar level gauge system and transmission line probe which can be used in particular for accurate measurement of (cereal) grain contained in a silo.

[0005] According to a first aspect of the present invention, this object and other objects are achieved by a transmission line probe for use in a radar level gauge system, which is configured to determine the filling level and density of a product contained in a container, wherein the transmission line probe comprises: at least one probe wire, which is suitable for guiding an electromagnetic transmission signal toward the product and guiding the electromagnetic transmission signal at least partially through the product, and guiding the electromagnetic return signal back from the surface of the product or an interface below the surface; and a plurality of insulating dielectric beads, which are arranged along the at least one probe wire and are configured to reduce the attenuation of the electromagnetic signal caused by the product.

[0006] "Density" is to be understood here as volumetric mass density (mass per unit volume). The product may be (cereal) grains. The container may be, for example, a silo. The at least one probe wire may be at least one wire. "Insulation" may be interpreted as meaning that the bead is configured to protect the electromagnetic signal along the at least one probe wire from attenuation caused by the product.

[0007] The present invention is based, at least in part, on the understanding that a plurality of insulating dielectric beads enables measurements to be made within the product—possibly all the way to the lower end of the transmission line probe—without the (cereal) grains attenuating the electromagnetic emission signal (excessively), which would otherwise be the case without the insulating dielectric beads. In this way, as will be further explained below, it is possible to determine not only the fill level of the product in the container but also the density of the product in the container. For a bare probe wire (without the insulating dielectric beads), the attenuation caused by the grains might be 30 dB to 40 dB per meter, making measurements through the product virtually impossible. It will be noted that dielectric structures that substantially surround the probe wire are previously known, the surrounding structures being arranged to reduce the attenuation effects of microwave energy caused by the contents to be measured, e.g., see, for example, US2007090992 (Edvardsson), where the exemplified content is oil. The contents of US2007090992 are incorporated herein by reference. However, the inventors have realized that for solids such as (cereal) grains, the insulating dielectric means does not have to seal at least one probe wire. On the contrary, some gap can be allowed at least temporarily as long as the gap is smaller than the grain. The inventors have also realized that for grains, the insulating dielectric means may have to be relatively thick, which will make a conventional transmission line probe with a dielectric surround structure stiff. To this end, the inventors have designed insulating dielectric beads arranged along at least one probe wire. The insulating dielectric beads can, for example, be threaded on at least one probe wire so that the transmission line probe is flexible (a bit like a beaded necklace), which facilitates transportation and installation. The transmission line probe may be >30m in length and can, for example, be rolled up during transportation.

[0008] To quantify the degree of insulation required, the transmission velocity can be used (which is necessary to know when measuring distance). The present transmission line probe can have a velocity reduction factor of 0.9 or greater. A transmission line probe designed with such a velocity reduction factor can sufficiently reduce the attenuation of the electromagnetic signal while giving a useful surface echo. In comparison, for a bare probe wire, the velocity reduction factor is 1 / square root (DC) (1 / sqrt(DC)), which is about 0.5 for grain and about 0.65 to 0.7 for oil. The velocity reduction factor indicates how much slower the electromagnetic signal propagates along or in the transmission line probe when the transmission line probe is in the product compared to when the transmission line probe is in the atmosphere (air). In other words, the velocity reduction factor compares the propagation velocity of the insulated transmission line probe when it is in air to the same transmission line probe when it is immersed in the product to be tested (grain, etc.). The velocity reduction factor can also be a measure of the "insulation" provided by the multiple insulating dielectric beads. Unless otherwise expressed, the present transmission line probe can be configured so that the reduction in velocity (of the electromagnetic signal) is less than four times the reduction that would occur if the uninsulated probe wire were immersed in the product, less than the reduction that would occur if the uninsulated probe wire were immersed in the product, but always greater than 2% to 3%. The propagation velocity is the square root (1 / LC tot )(sqrt(1 / LC tot )), where L is the inductor, and C tot Capacitance per meter, including losses in surrounding material (both insulating dielectric beads and product), see further below.

[0009] In addition, in the case where at least one probe line is a dual probe line, see Figure 8 , a transmission line probe can be described by three capacitors C0, C1, C2, where C1 and C2 are connected in series, and where C0 is connected in parallel with C1 and C2. C2 (in use) is filled with the product in the container, and C0 and C1 have a plurality of insulating dielectric beads of plastic or ceramic material as dielectric fillers. Figure 8 In the example, capacitance C1 is divided into two times 2C1 to emphasize that the product is not normally in contact with any probe wire. Preferably, the transmission line probe is configured so that the total capacitance C is 2C1 when the transmission line probe is immersed in oil compared to when the transmission line probe is surrounded by air. tot (actual line capacitance per meter) does not increase by more than 10%, more preferably not more than 5%. Figure 8It is understood that the increase in capacitance when a transmission line probe is immersed (compared to air) depends somewhat on the surrounding product (a certain type of grain in the case of the transmission line probe), and with proper insulation, the increase in capacitance will be 5% to 10%. A characteristic of this type of insulated transmission line probe is that the increase in capacitance (compared to being immersed through air) is much smaller than that of a bare probe wire, and this is especially true for losses associated with the imaginary part of the complex dielectric constant. Figure 8 As can be seen in Figure 3, even very high or very high loss dielectric constants outside the transmission line probe have limited effect on the propagation of the transmission line probe.

[0010] In addition, the plurality of insulating dielectric beads can be configured so that when the transmission line probe is surrounded by grain, the maximum bidirectional electromagnetic signal attenuation caused by the product is ≤ 0.3 dB per meter, or no more than 20 dB for the entire transmission line probe. For most types, the grain has a dielectric constant of 4 and a loss tangent close to 0.1. This allows measurements to be made all the way to the lower end of the transmission line probe (i.e., typically to the bottom of the container) even for long transmission line probes. Typically for GWR systems, a dielectric constant of 4 and a loss tangent close to 0.1 gives an attenuation of about 40 dB / m at 1 GHz for a bare probe wire.

[0011] The transmission line probe may further include reflectors arranged at fixed, predetermined positions along at least one probe line, wherein each of the reflectors is configured to reflect a portion of the electromagnetic transmission signal. With the aid of the reflectors, the density of the contents at different levels along the transmission line probe can be determined. Here, "predetermined position" should be understood to mean that the distance to the reflector is known. It should be noted that the use of reflectors along the probe line to determine density is previously known from NO 331 262 (KONGSBERG MARITIME AS), but for liquids with very low radar loss, rather than for lossy materials such as grain. Alternatively, or in addition to the reflectors, the average density can be determined based on reflections from the lower end of the transmission line probe, which can be achieved using insulating dielectric beads. However, with the aid of the aforementioned reflectors, regardless of the insulating dielectric beads, one or more density determinations can also be obtained at higher locations, even if the electromagnetic transmission signal does not reach the lower end of the transmission line probe.

[0012] The reflectors may be included in some of the plurality of insulating dielectric beads. In other words, some of the plurality of insulating dielectric beads may each include at least one of the reflectors. In this way, the portion of at least one probe wire provided with the reflector may also be insulated to reduce electromagnetic signal attenuation. The reflector may, for example, be a metal insert in the plastic or ceramic material of the insulating dielectric beads. The metal insert may, for example, be a ring or a cylindrical tube embedded in the plastic or ceramic material of the insulating dielectric beads. Alternatively, the metal insert may be, for example, a U-shaped member clamped onto the probe wire, wherein the plastic or ceramic material of the insulating dielectric beads is arranged around the U-shaped member.

[0013] One or more of the plurality of insulating dielectric beads may be fixedly attached to at least one probe wire (while other insulating dielectric beads may be more loosely attached to at least one probe wire). This means that the fixedly attached insulating dielectric bead only has to bear the load caused by friction between the product up to the next fixedly attached insulating dielectric bead and the insulating dielectric bead, thereby distributing the load along the transmission line probe.

[0014] Preferably, the insulating dielectric bead comprising the reflector is fixedly attached to the at least one probe wire.Thus, the fixedly attached insulating dielectric bead may advantageously have two purposes: the aforementioned load distribution and ensuring that the reflector is disposed at a fixed predetermined position along the at least one probe wire.

[0015] The plurality of insulating dielectric beads may surround at least a substantial portion of the at least one probe line. In this manner, suitable attenuation may be achieved. For a 30 m transmission line probe, any unenclosed portion of the at least one probe line is preferably no larger than 1 dm or 2 dm overall.

[0016] Furthermore, the plurality of insulating dielectric beads are preferably solid (not hollow) or substantially solid. This can help achieve a substantial reduction in electromagnetic signal attenuation caused by the product. The plurality of (substantially) solid insulating dielectric beads can, for example, have a distance of at least 3 mm from the solid material of the outer surface of the insulating dielectric beads so that the at least one probe wire is away from the outer surface of the insulating dielectric beads.

[0017] The insulating dielectric beads of the plurality of insulating dielectric beads may each have a height in the range of 50 mm to 250 mm, preferably in the range of 100 mm to 200 mm. This may enable the transmission line probe to be rolled up (e.g., for transport) without excessive inter-bead joints where moisture may accumulate.

[0018] The plurality of insulating dielectric beads may be arranged such that the maximum distance (gap) between subsequent insulating dielectric beads in the plurality of insulating dielectric beads is less than 2 mm or less than 1 mm. This can prevent grain from entering between subsequent insulating dielectric beads (which would otherwise increase attenuation) while providing gaps between subsequent insulating dielectric beads that are large enough to avoid possible accumulation of condensed water.

[0019] Each of the plurality of insulating dielectric beads may have opposing surfaces adapted to face another insulating dielectric bead, the opposing surfaces comprising a convex first surface and a concave second surface. This can facilitate rolling up the transmission line probe. The first convex surface can be rounded outwardly, like the exterior of a sphere. The second concave surface can be rounded inwardly, for example, like the interior of a bowl. In use, the first convex surface is preferably the top surface, while the second concave surface is the bottom surface. This can improve moisture drainage. Furthermore, the first and second surfaces are preferably complementary. This can prevent, or at least reduce, the risk of product entering between two adjacent insulating dielectric beads. In another embodiment, the first and second surfaces can be flat.

[0020] The at least one aforementioned probe line can be a dual (=two) probe line. To this end, each of the plurality of insulating dielectric beads can have two holes, one for each transmission line. The dual probe lines (and the holes for the two probe lines) are typically parallel. Alternatively, the at least one aforementioned probe line can be a single probe line.

[0021] At least some of the plurality of insulating dielectric beads may each have at least one hole configured to reduce the local dielectric constant. This can be used to adjust the coupling between the two probe lines mentioned above. The at least one hole may be parallel to the probe lines, i.e., generally vertical during operation. The at least one hole may, for example, be a recess located between the two probe lines.

[0022] According to a second aspect of the present invention, a radar level gauge system is provided, which is configured to determine the filling level and density of a product contained in a container, wherein the radar level gauge system includes: a transceiver circuit configured to generate and transmit an electromagnetic transmit signal and receive an electromagnetic return signal; a transmission line probe according to the first aspect; and a processing circuit configured to determine the filling level of the product contained in the container based on the relationship between the electromagnetic transmit signal and the electromagnetic return signal, and to determine the density of the product contained in the container based on one or more electromagnetic reflection signals generated by the transmission line probe. The one or more electromagnetic reflection signals can be generated, for example, by the aforementioned reflector and / or the (lower) end of the transmission line probe. This aspect can exhibit the same or similar features and technical effects as the first aspect, and conversely, the first aspect can also exhibit the same or similar features and technical effects as this aspect.

[0023] According to a third aspect of the present invention, a method for determining a fill level and density of a product contained in a container is provided, wherein the method comprises: generating and emitting an electromagnetic emission signal; directing the electromagnetic emission signal toward the product and at least partially through the product using at least one probe line of a transmission line probe, wherein the transmission line probe further comprises a plurality of insulating dielectric beads arranged along the at least one probe line and configured to reduce attenuation of the electromagnetic signal caused by the product; directing an electromagnetic return signal back from a surface or interface of the product using the at least one probe line, and directing one or more electromagnetic reflector signals generated by the transmission line probe; determining a fill level of the product contained in the container based on a relationship between the electromagnetic emission signal and the electromagnetic return signal; and determining a density of the product contained in the container based on the one or more electromagnetic reflector signals. Determining the fill level and density may be performed by the aforementioned processing circuit. This aspect may exhibit the same or similar features and technical effects as the first and / or second aspects, and conversely, the first and / or second aspects may also exhibit the same or similar features and technical effects as this aspect.

[0024] The product may be cereal grains. Alternatively, the product may be some other granular material such as plastic pellets. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be described in more detail with reference to the accompanying drawings, which show currently preferred embodiments of the invention.

[0026] Figure 1 is a schematic side view of a radar level gauge system according to an embodiment of the present invention.

[0027] Figure 2 is a cross-sectional partial side view of a transmission line probe according to an embodiment of the present invention.

[0028] Figure 3a to Figure 3b yes Figure 2 Cross-sectional view of a transmission line probe.

[0029] Figure 4 Schematically shows the rolled Figure 2 transmission line probe.

[0030] Figures 5a to 5c Insulating dielectric beads according to other embodiments of the present invention are shown.

[0031] Figure 6 is Figure 1 The tank signal is generated by the radar level gauge system.

[0032] Figure 7 is a flow chart of a method according to an embodiment of the present invention.

[0033] Figure 8 An equivalent of an embodiment of the present transmission line probe is shown. DETAILED DESCRIPTION

[0034] Figure 1 A radar level gauge system 10 according to an embodiment of the present invention is shown. The radar level gauge system 10 can be a time domain reflectometry (TDR) radar level gauge system. The radar level gauge system 10 is mounted to a container 12. Here, the container 12 is a silo. The container 12 can be, for example, 20 to 30 meters high. The radar level gauge system 10 is configured to determine a filling level L and at least one density ρ of a product 14 contained in the container 12. The product 14 can be cereal grains, such as rice, corn, wheat, etc. The cereal grains can have a grain size of, for example, up to 20 mm.

[0035] The radar level gauge system 10 comprises a transceiver circuit 16, a transmission line probe 18 and a processing circuit 20. The transceiver circuit 16 is (electrically) connected to the transmission line probe 18 and the processing circuit 20.

[0036] The transceiver circuit 16 is configured to generate and transmit an electromagnetic transmit signal S T , and receiving an electromagnetic return signal S reflected by the surface 22 of the product 14 R The transceiver circuit 16 may be one unit capable of both transmitting and receiving, or may include separate transmitter and receiver units.

[0037] The transmission line probe 18 may be arranged vertically in the vessel 12 and may extend from the top of the vessel 12 to the entire depth or nearly the entire depth of the vessel 12. The transmission line probe 18 may, for example, have a length in the range of 15 m to 50 m. The transmission line probe 18 has a (lower) end 19.

[0038] Further references Figure 2 and Figure 3a to Figure 3b , the transmission line probe 18 includes at least one probe wire, here two probe wires 24a to 24b (= double probe wire). The two probe wires 24a to 24b can be parallel. The probe wires 24a to 24b can be wires. The probe wires 24a to 24b can be flexible. The probe wires 24a to 24b can be made of (stainless) steel, for example. The probe wires 24a to 24b can also be called leads or conductors. The probe wires 24a to 24b can each have a diameter in the range of 6 mm to 8 mm, for example. The probe wires 24a to 24b are suitable for transmitting the electromagnetic transmission signal S from the transceiver circuit 16 to the transceiver circuit 16. T Directs and guides the electromagnetic emission signal S downward T through the product 14 in the container 12 and directing the electromagnetic return signal S R Returning from the surface 22 makes the electromagnetic return signal S R can be received by the transceiver circuit 16 .

[0039] The transmission line probe 18 also includes a plurality of insulating dielectric beads 26. The insulating dielectric beads 26 are configured to reduce electromagnetic signal attenuation caused by the product 14 by limiting the electric field outside the insulating dielectric beads 26. That is, as discussed in the Summary of the Invention, the insulating dielectric beads 26 can be configured to reduce electromagnetic signal attenuation caused by the product 14 by providing insulation with a velocity reduction factor of 0.9 or greater. The insulating dielectric beads 26 can be arranged behind and adjacent to each other along substantially the entire length of the two probe wires 24a-24b. In this manner, the insulating dielectric beads 26 can surround at least a majority of the probe wires 24a-24b. The insulating dielectric beads 26 can be threaded onto the two probe wires 24a-24b. To this end, each insulating dielectric bead 26 can have two through-holes 28a and 28b, one for each probe wire 24a-24b. The through holes 28a-28b may be (slightly) wider than the probe wires 24a-24b to simplify installation of the insulating dielectric beads 26 and / or facilitate winding of the transmission line probe 18. For a probe wire 24a-24b having a diameter of 6 mm, the diameter of the through holes 28a-28b may be, for example, 7.5 mm. In addition, the through holes 28a-28b may be tapered (wider) at the ends to facilitate winding of the transmission line probe 18. Figure 4 The transmission line probe 18 is schematically shown rolled up.

[0040] Each insulating dielectric bead 26 can be (substantially) solid. In other words, each insulating dielectric bead 26 can be non-hollow. The insulating dielectric bead 26 can be made of, or include, a plastic or ceramic material 30, such as PTFE (polytetrafluoroethylene), PEEK (polyetheretherketone), or PE (polyethylene), or porcelain or ceramic particles in a plastic. Furthermore, the insulating dielectric bead 26 can generally be shaped like a rectangular parallelepiped or a solid elliptical cylinder. The outer side of the insulating dielectric bead 26 facing the product 14 is preferably smooth to reduce friction with the product 14. The insulating dielectric bead 26 can, for example, have a base of 12 mm to 30 mm by 18 mm to 52 mm (thickness x width), and a height H in the range of 50 mm to 250 mm, preferably in the range of 100 mm to 200 mm. The distance D separating the probe wires 24 a and 24 b from the outer surface of the insulating dielectric bead 26 can be at least 3 mm. For an insulating dielectric bead 26 having a base of 20 mm x 45 mm, the CC (center-to-center) distance between the two probe wires 24 a and 24 b (corresponding to the CC distance between the through holes 28 a and 28 b) may be, for example, in the range of 11 mm to 13 mm. A wider CC distance may result in excessive attenuation, and a narrower CC distance may excessively reduce the electromagnetic return signal S R In general, the CC distance is preferably about 0.75 times (or 75%) the thickness d of the insulating dielectric bead 26 .

[0041] The opposite surfaces 32a to 32b are adapted to face the other insulating dielectric bead 26, i.e. Figure 2 The top and bottom surfaces shown may be (slightly) convex and concave, respectively. The surfaces 32a-32b may be complementary. That is, the top surface 32a of one insulating dielectric bead 26 may mate with the bottom surface 32b of the other insulating dielectric bead 26 immediately above. Two through-holes 28a-28b extend between the surfaces 32a-32b. At least some of the insulating dielectric beads 26 may also have at least one vertical hole configured to reduce the local dielectric constant. Figure 2 In FIG. 3 , at least one vertical hole is a recess 34 located between two probe lines 24 a - 24 b and extending from the top surface 32 a .

[0042] Here, some of the insulating dielectric beads, indicated at 26', include reflectors 36. The reflectors 36 are generally configured to reflect the aforementioned electromagnetic emission signal S T A (small) part of the electromagnetic reflector signal S X . Electromagnetic reflector signal S XThe light can be guided (returned) from the reflector 36 via the probe wires 24a to 24b and received by the transceiver circuit 16. The distance between the insulating dielectric beads 26' can be several meters. For example, every 10th to 20th insulating dielectric bead can be an insulating dielectric bead 26' including the reflector 36.

[0043] The reflector 36 may be, for example, at least one metal insert in the plastic or ceramic material 30 of the insulating dielectric bead 26'. The reflector 36 / metal insert may be made of, for example, stainless steel. Figure 2 In the embodiment of FIG. 1 , each reflector 36 comprises two rings or cylindrical tubes 38 a - 38 b embedded in the plastic or ceramic material 30 at each through hole 28 a - 28 b of the bead 26 ′ such that the probe wires 24 a - 24 b pass through the rings / cylindrical tubes 38 a - 38 b.

[0044] The reflector 36 should be arranged at a fixed predetermined position along the probe wire 24a to 24b. "Predetermined" means that the distance from a reference position, usually at the top of the container 12, to the reflector 36 is known. To this end, the insulating dielectric bead 26' including the reflector 36 is fixedly attached to the probe wire 24a to 24b, for example, by means of a screw 40 that passes through the plastic or ceramic material 30 and the metal insert 38a to 38b and into the probe wire 24a to 24b.

[0045] Other insulating dielectric beads 36 may be more loosely attached to the probe wires 24a to 24b, thereby allowing some movement of the insulating dielectric beads 26 along the probe wires 24a to 24b. The plurality of insulating dielectric beads 26, 26' may be arranged so that the maximum distance (gap) 42 between subsequent insulating dielectric beads 26, 26' is less than 2 mm. Depending on the circumstances, the surface 32a of one insulating dielectric bead 26, 26' may abut the surface 32b of another adjacent insulating dielectric bead 26, 26'.

[0046] Figures 5a to 5c An alternative design of insulating dielectric beads 26 , 26 ′ is shown.

[0047] exist Figure 5aIn the embodiment shown in FIG. 1 , the insulating dielectric bead 26 has outer cutouts or slots 41 a - 41 b corresponding to the through-holes 28 a - 28 b, respectively, and the material 30 is elastic. Here, the insulating dielectric bead 26 can be positioned on the probe wires 24 a - 24 b by passing the probe wires 24 a - 24 b through the corresponding cutouts or slots 41 a - 41 b. Thus, there is no need to thread the insulating dielectric beads 26 onto the probe wires 24 a - 24 b. The cutouts or slots 41 a - 41 b can be spirally shaped so that once the probe wires 24 a - 24 b are in the proper mounting position, it is impossible, or at least very difficult, for the probe wires 24 a - 24 b to pass through the cutouts or slots 41 a - 41 b.

[0048] exist Figure 5b In the embodiment of the present invention, the metal inserts 38a to 38b are two U-shaped or C-shaped members that are clamped or screwed onto each probe wire 24a to 24b. In addition, the plastic or ceramic material 30 of the insulating dielectric bead 26' is in two parts 30' and 30". In this way, the plastic or material 30 can be arranged around the U-shaped or C-shaped members 38a to 38b after they are attached to the probe wires 24a to 24b. As the skilled person will understand, once the two parts 30' and 30" are brought together, they can be joined in various ways. The joint 45 between the two parts 30' and 30" is perpendicular to the base of the insulating dielectric bead 26' and passes through the two through holes 28a to 28b. The two-part plastic or ceramic material 30 can also be applied to the insulating dielectric bead 26 without any reflector 36 / metal inserts 38a to 38b.

[0049] exist Figure 5c , the transmission line probe 18 has a single probe wire 24, and therefore the insulating dielectric bead 26 has one through hole 28. Here, the transmission line probe 18 is pressed into a U-shaped or C-shaped profile 43. The profile 43 and the insulating dielectric bead 26 can be formed so that the transmission line probe 18 can also be fixed to the profile 43 when the material 30 of the insulating dielectric bead 26 is somewhat deformed. The profile 43 can form part of the radar level gauge system 10 mentioned above. The profile 43 can be made of a metal material, such as (extruded) aluminum. The profile 43 can be arranged vertically. The profile 43 can be attached to the inner wall of the container 12, for example, along a ladder in the container 12, along a vertical pipe in the container 12, etc. In addition, the profile 43 can be divided into sections of, for example, several meters to facilitate transportation.

[0050] Back to Figure 1 The processing circuit 20 is configured to process the electromagnetic emission signal S T With the electromagnetic return signal S R Specifically, the processing circuit 20 can determine the filling level L of the product 14 contained in the container 12 based on the relationship between the electromagnetic emission signal ST With the electromagnetic return signal S R The time delay between 1 and 2 determines the distance from a reference position at the top of the container 12 to the surface 22 of the product 14, from which the filling level L can be determined. Figure 6 An exemplary signal (tank spectrum) where the echo of the surface 22 is indicated by 44 is shown in FIG.

[0051] The processing circuit 20 is further configured to generate an electromagnetic reflector signal S based on the electromagnetic reflector signal S generated by the reflector 36. X To determine the density ρ of the product 14 contained in the container 12. Figure 6 , the echoes of the three reflectors 36 below the surface 22 are indicated by 46. At least for the reflectors 36 below the surface 22, the processing circuit 20 may, for example, calculate the echoes based on the known distances of the reflectors 36 and the electromagnetic emission signal S T With the electromagnetic reflector signal S X The electromagnetic signal velocity and attenuation are determined based on the time delay between the two. The determined electromagnetic signal velocity and attenuation in the product 14 depend on the dielectric constant of the product 14, which in turn is related to the density ρ of the product 14. Therefore, the density ρ of the product 14 can be determined.

[0052] By means of the determined filling level L and density ρ, the mass and / or moisture content of the (cereal) grains 14 contained in the container 12 can be determined, for example according to predetermined tables for different types of grain.

[0053] The processing circuit 20 may be connected to a memory 48 of the radar level gauge system 10 , which memory 48 may store any software (computer program product) required for the operation of the radar level gauge system 10 .

[0054] The radar level gauge system 10 may further include an interface 50 for transmitting the determined filling level and density outside the radar level gauge system 10. The interface 56 may be, for example, wireless (e.g., WirelessHART) or wired (e.g., a two-wire 4-20 mA loop, HART, etc.). In the case where the interface 50 is wireless, the radar level gauge system 10 may further include a local power supply such as a battery pack.

[0055] Figure 7 is a flow chart of a method for determining the filling level L and the density of a product 14 contained in a container. The method may be performed, for example, using the radar level gauge system 10. Thus, the method may correspond to the operation of the radar level gauge system 10.

[0056] At S1 , the method may include generating and transmitting an electromagnetic transmit signal S comprising one or more pulses. T This step may be performed by the transceiver circuit 16 .

[0057] The electromagnetic transmission signal S is guided toward the product 14 by means of the probe lines 24a to 24b of the transmission line probe 18. T , guide electromagnetic emission signal S T Enters the product and passes through the product 14 (S2).

[0058] The electromagnetic transmission signal S is reflected by the surface 22 T Some electromagnetic emission signals S T To generate electromagnetic return signal S R (S3), and the electromagnetic emission signal S T Some electromagnetic emission signals S T Continuing downward through the product 14, these electromagnetic emission signals S T is reflected by the reflector 36 to generate an electromagnetic reflector signal S X (S4).

[0059] The electromagnetic return signal S is guided by means of the probe wires 24a to 24b R and the electromagnetic reflector signal S X Return (S5).

[0060] At S6, based on the electromagnetic emission signal S T With the electromagnetic return signal S R The filling level L of the product 14 contained in the container 12 is determined based on the relationship between .

[0061] At S7, based on the electromagnetic reflector signal S generated by the reflector 36 X One or more electromagnetic reflector signals S X The density of the product 14 contained in the container 12 is determined.

[0062] Steps S6 to S7 may be performed by the processing circuit 20. Steps S6 to S7 may be computer-implemented.

[0063] It will be appreciated by those skilled in the art that the present invention is by no means limited to the preferred embodiments described above. Instead, many modifications and variations are possible within the scope of the appended claims.

Claims

1. A transmission line probe (18) for use in a radar level gauge system (10) configured to determine a fill level (L) and a density of a product (14) contained in a container (12), wherein: The transmission line probe comprises: At least one probe wire (24a, 24b) adapted to direct an electromagnetic emission signal (S) towards the product T ) and guide the electromagnetic emission signal (S T ) at least partially through the product, and directing an electromagnetic return signal (S R ) returns from the surface (22) of the product or an interface below the surface of the product; and a plurality of insulating dielectric beads (26, 26') arranged along the at least one probe wire and configured to reduce electromagnetic signal attenuation caused by the product, wherein the transmission line probe further comprises reflectors (36) disposed at fixed predetermined positions along the at least one probe line, wherein each of the reflectors is configured to reflect a portion of the electromagnetic transmit signal; wherein the reflector is included in some of the plurality of insulating dielectric beads (26'); wherein the density of the product contained in the container is based on one or more electromagnetic reflector signals (S X ).

2. The transmission line probe according to claim 1, wherein the plurality of insulating dielectric beads arranged along the at least one probe wire being configured to reduce electromagnetic signal attenuation caused by the product by providing insulation with a velocity reduction factor of 0.9 or more; wherein the velocity reduction factor indicates that the electromagnetic signal (S) is slower when the transmission line probe is in the product (14) than when the transmission line probe is in air. T , S R ) propagates along or in the transmission line probe.

3. The transmission line probe according to claim 1, wherein The reflector is a metal insert (38a, 38b) in the plastic or ceramic material (30) of the insulating dielectric bead.

4. The transmission line probe according to any one of the preceding claims 1 to 3, wherein: One or more insulating dielectric beads of the plurality of insulating dielectric beads are fixedly attached to the at least one probe wire.

5. The transmission line probe according to claim 1, wherein An insulating dielectric bead (26') including a reflector (36) is fixedly attached to the at least one probe wire.

6. The transmission line probe according to any one of the preceding claims 1 to 3 and 5, wherein: The plurality of insulating dielectric beads surround at least a majority of the at least one probe wire.

7. The transmission line probe according to any one of claims 1 to 3 and 5, wherein: The plurality of insulating dielectric beads are solid or substantially solid.

8. The transmission line probe according to any one of the preceding claims 1 to 3 and 5, wherein The insulating dielectric beads of the plurality of insulating dielectric beads each have a height in a range of 50 mm to 250 mm.

9. The transmission line probe according to claim 8, wherein: The height is in the range of 100 mm to 200 mm.

10. The transmission line probe according to any one of the preceding claims 1 to 3, 5 and 9, wherein The plurality of insulating dielectric beads are arranged such that a maximum distance (42) between subsequent insulating dielectric beads in the plurality of insulating dielectric beads is less than 2 mm. The transmission line probe according to claim 10 , wherein: A maximum distance (42) between subsequent insulating dielectric beads in the plurality of insulating dielectric beads is less than 1 mm.

12. The transmission line probe according to any one of claims 1 to 3, 5, 9 and 11, wherein Each of the plurality of insulating dielectric beads has opposing surfaces (32a-32b) adapted to face another insulating dielectric bead, the opposing surfaces including a convex first surface (32a) and a concave second surface (32b).

13. The transmission line probe according to any one of the preceding claims 1 to 3, 5, 9 and 11, wherein The at least one probe line is a dual probe line.

14. The transmission line probe according to claim 13, wherein: At least some of the plurality of insulating dielectric beads each have at least one hole (34) configured to reduce a local dielectric constant.

15. A radar level gauge system (10) configured to determine the filling level (L) and density of a product (14) contained in a container (12), wherein: The radar level gauge system comprises: A transceiver circuit (16) configured to generate and transmit an electromagnetic transmit signal (S T ), and receive electromagnetic return signals (S R ); A transmission line probe (18) according to any one of the preceding claims; and processing circuitry (20) configured to determine a fill level of the product contained in the container based on a relationship between the electromagnetic transmit signal and the electromagnetic return signal, and based on one or more electromagnetic reflector signals (S X ) to determine the density of the product contained in the container.

16. A method for determining the filling level (L) and density of a product (14) contained in a container (12), wherein: The method comprises: Generate and transmit electromagnetic emission signal (S T ); The electromagnetic emission signal (S) is directed toward the product by means of at least one probe line (24a, 24b) of a transmission line probe (18). T ) and guide the electromagnetic emission signal (S T ) at least partially through the product, wherein the transmission line probe further comprises a plurality of insulating dielectric beads (26, 26') arranged along the at least one probe line and configured to reduce electromagnetic signal attenuation caused by the product; By means of the at least one probe wire, an electromagnetic return signal (S R ) back from the surface (22) or interface of the product and directing one or more electromagnetic reflector signals (S) generated by the transmission line probe X ), wherein the transmission line probe further comprises reflectors (36) arranged at fixed predetermined positions along the at least one probe line, wherein each of the reflectors is configured to reflect a portion of the electromagnetic transmit signal, wherein the reflector is included in some of the plurality of insulating dielectric beads (26'); determining a fill level of the product contained in the container based on a relationship between the electromagnetic emission signal and the electromagnetic return signal; and A density of the product contained in the container is determined based on the one or more electromagnetic reflector signals.

17. The method according to claim 16, wherein The product is cereal grains.

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