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A radar level gauge using comprising a transceiver, processing circuitry, a signal propagating device, and a wave guide arrangement connecting the transceiver with the signal propagation device. The wave guide arrangement includes a hollow wave guide, a first filling member made of a first dielectri

A radar level gauge using comprising a transceiver, processing circuitry, a signal propagating device, and a wave guide arrangement connecting the transceiver with the signal propagation device. The wave guide arrangement includes a hollow wave guide, a first filling member made of a first dielectric material, which first filling member is arranged inside the hollow wave guide, and a second filling member made of a second dielectric material, which second filling member is arranged inside the hollow wave guide outside the first filling member with respect to the tank. The second filling member is fixed in the wave guide at least in a direction out from the tank, and is configured to withstand temperatures up to 250 degrees Celsius. During conditions of temperatures sufficiently high to soften the inner filling member, the outer filling member will thus serve to prevent the first filling member from being forced out of the wave guide.

대표청구항 ▼

1. A radar level gauge using electromagnetic waves for determining a filling level of a product in a tank, said radar level gauge comprising: a transceiver for transmitting an electromagnetic transmit signal and receiving an electromagnetic echo signal;processing circuitry connected to said transcei

1. A radar level gauge using electromagnetic waves for determining a filling level of a product in a tank, said radar level gauge comprising: a transceiver for transmitting an electromagnetic transmit signal and receiving an electromagnetic echo signal;processing circuitry connected to said transceiver for determining said filling level based on said electromagnetic echo signal;a signal propagating device adapted to direct said electromagnetic transmit signal towards a surface of said product and to return a reflection from said surface as said electromagnetic echo signal, anda wave guide arrangement, connecting said transceiver with said signal propagation device, said wave guide arrangement including a hollow wave guide, comprising an inner portion formed by a first electrically conducting wave guide forming member, and an outer portion formed by a second electrically conducting wave guide forming member, anda first dielectric wave guide filling member having an elongated center portion with an inner end oriented towards the inner wave guide portion and an outer end oriented towards the outer wave guide portion, and a cup-shaped sleeve portion having a radial portion extending from said center portion and an axial portion extending from said radial portion, wherein said radial portion is located between said first and second wave guide forming members,a second dielectric wave guide filling member, which second filling member is arranged inside the hollow wave guide outside said first filling member with respect to said tank, wherein said second filling member is fixed in said wave guide at least in a direction out from said tank,wherein said second dielectric wave guide filling member is configured to withstand 250 degrees Celsius. 2. The radar level gauge according to claim 1, wherein said second wave guide filling member is configured to withstand 500 degrees Celsius. 3. The radar level gauge according to claim 1, wherein said second wave guide filling member is made of a dielectric material selected from the group of ceramics, epoxy resin, glass and aluminum oxide. 4. The radar level gauge according to claim 1, wherein said first wave guide filling member is made of a dielectric material selected from the group of PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy), FEP (fluorinated ethylene propylene) and PPS (polyphenylene sulfide). 5. The radar level gauge according to claim 1, wherein said second wave guide filling member is arranged in said outer portion. 6. The radar level gauge according to claim 5, wherein said wave guide arrangement further comprises a first sealing element between said first wave guide filling member and said first wave guide forming member, thereby providing a process seal of said tank. 7. The radar level gauge according to claim 6, wherein said wave guide arrangement further comprises a second sealing element between said first wave guide filling member and said second electrically conducting wave guide forming member. 8. The radar level gauge according to claim 1, wherein said axial portion extends axially from the radial portion in a direction out from the tank, such that said cup-shaped sleeve portion has an opening facing away from said tank. 9. The radar level gauge according to claim 1, wherein said wave guide arrangement further comprises at least one channel providing fluid contact between an outer rim of said cup-shaped sleeve portion to an exterior of said tank. 10. The radar level gauge according to claim 1, further comprising at least one sealing element in contact with said cup-shaped sleeve potion and adapted to provide a process seal of said tank, wherein walls of said sleeve portion, at least in places where said at least one sealing element is in contact with said sleeve portion, have a material thickness significantly smaller than the diameter of said center portion. 11. The radar level gauge according to claim 10, wherein said material thickness is less than 5 mm. 12. The radar level gauge according to claim 1, wherein said sleeve portion comprises an essentially cylindrical wall portion coaxial with the center portion, and a flat disc portion bridging a distance between the center portion and the wall portion. 13. The radar level gauge according to claim 12, wherein said disc portion extends essentially in a plane normal to a longitudinal axis of said hollow wave guide. 14. The radar level gauge according to claim 13, wherein a surface of said disc portion is provided with at least one annular protrusion, concentric with said longitudinal axis, said annular protrusion being formed to act as a quarter wave choke to prevent electromagnetic energy from escaping from said wave guide. 15. The radar level gauge according to claim 1, further comprising a tank connection arranged to be secured to the tank, said tank connection forming at least a portion of said wave guide. 16. The radar level gauge according to claim 1, wherein said signal propagating device comprises a directional antenna mounted to said tank connection. 17. The radar level gauge according to claim 1, wherein the axial portion of the first dielectric wave guide filling member is located outside said hollow wave guide. 18. A radar level gauge using electromagnetic waves for determining a filling level of a product in a tank, said radar level gauge comprising: a transceiver for transmitting an electromagnetic transmit signal and receiving an electromagnetic echo signal;processing circuitry connected to said transceiver for determining said filling level based on said electromagnetic echo signal;a signal propagating device adapted to direct said electromagnetic transmit signal towards a surface of said product and to return a reflection from said surface as said electromagnetic echo signal, anda wave guide arrangement, connecting said transceiver with said signal propagation device, said wave guide arrangement including a hollow wave guide, comprising an inner portion formed by a first electrically conducting wave guide forming member, and an outer portion formed by a second electrically conducting wave guide forming member, anda first dielectric wave guide filling member, having an elongated center portion with an inner end received in the inner wave guide portion and an outer end received in the outer wave guide portion, and a cup-shaped sleeve portion extending radially outwards from said center portion and axially along said center portion, said sleeve thus forming a cup-shape with an opening facing away from said tank, at least part of said sleeve portion being sandwiched between said first and second wave guide forming members. 19. The radar level gauge according to claim 18, wherein said wave guide arrangement further comprising at least one channel providing fluid contact between an outer rim of said cup-shaped sleeve to an exterior of said tank. 20. The radar level gauge according to claim 18, wherein said wave guide arrangement further comprises at least one sealing element in contact with said cup-shaped sleeve and adapted to provide a process seal of said tank, wherein walls of said sleeve, at least in places where said at least one sealing element is in contact with said sleeve, have a material thickness smaller than the diameter of said center portion. 21. The radar level gauge according to claim 20, wherein said material thickness is less than 5 mm. 22. The radar level gauge according to claim 20, wherein said wave guide arrangement comprises a first sealing element between said first filling member and said first wave guide forming member. 23. The radar level gauge according to claim 20, wherein said wave guide arrangement further comprises a second sealing element between said first filling member and said second wave guide forming member. 24. The radar level gauge according to claim 18, wherein said sleeve comprises an essentially cylindrical wall portion coaxially surrounding the center portion, and a flat disc portion bridging a distance between the center portion and the wall portion. 25. The radar level gauge according to claim 24, wherein said disc portion extends essentially in a plane normal to a longitudinal axis of said hollow wave guide. 26. The radar level gauge according to claim 25, wherein a surface of said disc portion is provided with at least one annular protrusion, concentric with said longitudinal axis, said annular protrusion being formed to act as a quarter wave choke to prevent electromagnetic energy from escaping from said wave guide. 27. The radar level gauge according to claim 18, wherein the first filling member is made of a first dielectric material, and wherein said wave guide arrangement further comprises a second filling member made of a second dielectric material, which second filling member is arranged in said outer wave guide portion so as to be fixed in said wave guide at least in a direction out from said tank, and wherein said second dielectric material is configured to withstand temperatures up to 250 degrees Celsius. 28. The radar level gauge according to claim 27, wherein said second dielectric material is configured to withstand temperatures up to 500 degrees Celsius. 29. The radar level gauge according to claim 27, wherein said second dielectric material is selected from the group of ceramics, epoxy resin, glass and aluminum oxide. 30. The radar level gauge according to claim 18, wherein said first dielectric filling member is made of a material selected from the group of PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy), FEP (fluorinated ethylene propylene) and PPS (polyphenylene sulfide). 31. The radar level gauge according to claim 18, further comprising a tank connection arranged to be secured to the tank, said tank connection forming at least a portion of said wave guide. 32. The radar level gauge according to claim 31, wherein said propagating device comprises a directional antenna mounted to said tank connection. 33. A method for assembling a wave guide arrangement for a radar level gauge, said method comprising the consecutive steps of: aranging a first electrically conducting wave guide forming member in an opening of a tank connection adapted to be secured to a tank, said first electrically conducting wave guide forming member forming an inner wave guide portion,arranging a first dielectric wave guide filling member inside the first electrically conducting wave guide forming member,arranging a second electrically conducting wave guide forming member on top of the first electrically conducting wave guide forming member, said second electrically conducting wave guide forming member forming an outer wave guide portion,wherein said first dielectric wave guide filling member has an elongated center portion with an inner end oriented towards the inner wave guide portion and an outer end oriented towards the outer wave guide portion, and a cup-shaped sleeve portion having a radial extension from said center portion and an axial extension from said radial extension, said radial extension being located between said first and second wave guide forming members. 34. The method according to claim 33, further comprising arranging a second dielectric wave guide filling member inside the first electrically conducting wave guide forming member, before the second electrically conducting wave guide forming member is arranged on top of the first electrically conducting wave guide forming member. 35. The method according to claim 33, further comprising arranging a first sealing element between said first wave guide filling member and said first wave guide forming member, thereby providing a process seal of said tank. 36. The method according to claim 33, further comprising arranging a second sealing element between said first filling member and said second wave guide forming member.