Radar level gauge and methods of testing radar level gauge and system
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
G01F-023/284
G01F-025/00
출원번호
US-0934969
(2013-07-03)
등록번호
US-9322699
(2016-04-26)
발명자
/ 주소
Korsbo, Thense
Skaug, Christian
Wennerberg, Tomas
Larsson, Michael
출원인 / 주소
Rosemount Tank Radar AB
대리인 / 주소
Westman, Champlin & Koehler, P.A.
인용정보
피인용 횟수 :
0인용 특허 :
9
초록▼
The present invention relates to a radar level gauge comprising a reference reflector arranged at a known reference reflector level in a tank. The radar level gauge is controllable between a filling level measuring state and a proof test state. In the proof test state, the radar level gauge is confi
The present invention relates to a radar level gauge comprising a reference reflector arranged at a known reference reflector level in a tank. The radar level gauge is controllable between a filling level measuring state and a proof test state. In the proof test state, the radar level gauge is configured to determine a first verification level based on a reference reflector echo resulting from reflection of an electromagnetic transmit signal at the reference reflector; determine a second verification level based on a surface echo resulting from reflection of an electromagnetic transmit signal at the surface of the product; and provide the first verification level and the second verification level to allow determination of a proof test result based on at least the first verification level, the known reference reflector level and the second verification level.
대표청구항▼
1. A method for testing a radar level gauge arranged at a tank containing a product, said radar level gauge comprising a reference reflector, the reference reflector being arranged at a known reference reflector level, wherein the method comprises the steps of: transmitting a plurality of electromag
1. A method for testing a radar level gauge arranged at a tank containing a product, said radar level gauge comprising a reference reflector, the reference reflector being arranged at a known reference reflector level, wherein the method comprises the steps of: transmitting a plurality of electromagnetic transmit signals towards a surface of said product in the tank;receiving a plurality of electromagnetic reflection signals, each including several echoes resulting from reflection of a corresponding one of said electromagnetic transmit signals at impedance discontinuities encountered by the electromagnetic transmit signal;determining a first verification level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at said reference reflector;determining a second verification level based on a surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product; anddetermining a test result based on a relation between said first verification level and said known reference reflector level, and on said second verification level;wherein said test result is determined to be positive only if: a difference between said first verification level and said known reference reflector level is less than a first threshold value. 2. The method according to claim 1, wherein said step of determining said first verification level further comprises the steps of: identifying said reference reflector echo; andtemporarily assigning said reference reflector echo as said surface echo. 3. The method according to claim 1, wherein said step of determining said second verification level further comprises the steps of: identifying said reference reflector echo;determining a set of surface echo candidates excluding said reference reflector echo; andassigning one surface echo candidate in said set of surface echo candidates as said surface echo. 4. The method according to claim 3, wherein said step of determining said second verification level further comprises the steps of: permanently arranging said reference reflector in a reference reflector position. 5. The method according to claim 1, wherein said test result is determined to be positive only if: said second verification level meets a predetermined level criterion based on prior surface echo measurements. 6. The method according to claim 1, wherein said test result is determined externally of said radar level gauge. 7. The method according to claim 1, further comprising the step of: determining a filling level of said product in the tank without using said radar level gauge,wherein said test result is additionally based on a relation between second verification level and said filling level. 8. The method according to claim 1, further comprising the step of: determining a filling level of said product in the tank by means selected from a set including: a second radar level gauge functionally independent of said radar level gauge, an ultrasonic level gauge, a float level gauge, a level measurement based on flow of said product, a level measurement based on pressure of said product, a level measurement based on capacitance of said product, a manual level measuring procedure such as hand-dipping;wherein said test result is additionally based on a relation between second verification level and said filling level. 9. The method according to claim 8, wherein said test result is determined based on a first difference between said first verification level and said known reference reflector level and a second difference between said second verification level and said filling level. 10. The method according to claim 9, wherein said test result is determined to be positive only if: said first difference is less than a first threshold value; andsaid second difference is less than a second threshold value. 11. The method according to claim 10, wherein said test result is determined to be positive only if: a ratio between said first difference and said first verification level is less than a third threshold value; anda ratio between said second difference and said second verification level is less than a fourth threshold value. 12. The method according to claim 10, wherein said first threshold value is less than said second threshold value. 13. The method according to claim 12, wherein said first threshold value is less than one half of said second threshold value. 14. The method according to claim 1, further comprising the steps of: when said tank is filled with said product to a first level above said reference reflector level: determining, using said radar level gauge, a first filling level;determining, without using said radar level gauge, a first reference filling level;when said tank is filled with said product to a second level below said reference reflector level:determining, using said radar level gauge, a second filling level;determining, without using said radar level gauge, a second reference filling level; anddetermining a test result based on a relation between said first filling level and said first reference filling level, and on a relation between said second filling level and said second reference filling level. 15. The method according to claim 1, further comprising the steps of: determining an amplitude of said reference reflector echo; anddetermining an amplitude of said surface echo. 16. The method according to claim 15, wherein said test result is determined to be positive only if: said amplitude of the reference reflector echo is in a predetermined first amplitude range. 17. The method according to claim 15, wherein said test result is determined to be positive only if: said amplitude of the surface echo is greater than said amplitude of the reference reflector echo. 18. The method according the claim 1, wherein said first verification level and said second verification level are determined based on reflections of the same electromagnetic transmit signal. 19. The method according the claim 1, wherein said first verification level and said second verification level are determined based on reflections of different electromagnetic transmit signals. 20. The method according to claim 1, wherein said known reference reflector level is stored in memory comprised in said radar level gauge. 21. The method according to claim 1, wherein said reference reflector is arranged at or above a high level alarm limit for said tank, and wherein said method further comprises the steps of: determining a proof test filling level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at the reference reflector; andproviding, to a host system externally of said radar level gauge, a signal indicative of the proof test filling level. 22. The method according to claim 21, wherein said radar level gauge is further controllable to operate in a filling level measuring state or a system proof test state, said method further comprising the steps of: determining in said radar level gauge a filling level of said product based on said surface echo;providing from said radar level gauge a signal indicative of said filling level to said host system;receiving, as an input to said radar level gauge, a system proof test start command;controlling, in response to said system proof test start command, said radar level gauge to enter said proof test state; andcontrolling, after having provided to said host system said signal indicative of the proof test filling level, said radar level gauge to exit said system proof test state. 23. The method according to claim 22, further comprising the step of: issuing said system proof test start command via said host system or via an operator input device located on said radar level gauge. 24. The method according to claim 22, wherein said step of determining said filling level in said level measuring state comprises the steps of: excluding said reference reflector echo from said several echoes; andidentifying said surface echo among remaining ones of said several echoes. 25. The method according to claim 22, further comprising the step of: controlling said radar level gauge to exit said system proof test state a predetermined time after entering said system proof test state. 26. The method according to claim 22, further comprising the steps of: determining the filling level while said radar level gauge is in said proof test state; andcontrolling, if a difference between said filling level and said high level alarm limit is smaller than a threshold value, said radar level gauge back to said filling level measuring state. 27. The method according to claim 22, wherein said radar level gauge is controlled back to said filling level measuring state after a predetermined period of time. 28. The method according to claim 21, wherein said step of determining said proof test filling level further comprises the steps of: identifying said reference reflector echo; andtemporarily assigning said reference reflector echo as said surface echo. 29. A method for testing a radar level gauge arranged at a tank containing a product, said radar level gauge comprising a reference reflector, the reference reflector being arranged at a known reference reflector level, wherein the method comprises the steps of: transmitting a plurality of electromagnetic transmit signals towards a surface of said product in the tank;receiving a plurality of electromagnetic reflection signals, each including several echoes resulting from reflection of a corresponding one of said electromagnetic transmit signals at impedance discontinuities encountered by the electromagnetic transmit signal;determining a first verification level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at said reference reflector;determining a second verification level based on a surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product; anddetermining a test result based on a relation between said first verification level and said known reference reflector level, and on said second verification level,wherein the method further comprises the step of: determining a filling level of said product in the tank by means selected from a set including: a second radar level gauge functionally independent of said radar level gauge, an ultrasonic level gauge, a float level gauge, a level measurement based on flow of said product, a level measurement based on pressure of said product, a level measurement based on capacitance of said product, a manual level measuring procedure such as hand-dipping,wherein said test result is additionally based on a relation between second verification level and said filling level,wherein said test result is determined based on a first difference between said first verification level and said known reference reflector level and a second difference between said second verification level and said filling level. 30. A method for testing a radar level gauge arranged at a tank containing a product, said radar level gauge comprising a reference reflector, the reference reflector being arranged at a known reference reflector level, wherein the method comprises the steps of: transmitting a plurality of electromagnetic transmit signals towards a surface of said product in the tank;receiving a plurality of electromagnetic reflection signals, each including several echoes resulting from reflection of a corresponding one of said electromagnetic transmit signals at impedance discontinuities encountered by the electromagnetic transmit signal;determining a first verification level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at said reference reflector;determining a second verification level based on a surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product; anddetermining a test result based on a relation between said first verification level and said known reference reflector level, and on said second verification level,wherein the method further comprises the steps of: determining an amplitude of said reference reflector echo; anddetermining an amplitude of said surface echo,wherein said test result is determined to be positive only if: said amplitude of the reference reflector echo is in a predetermined first amplitude range. 31. A method for testing a radar level gauge arranged at a tank containing a product, said radar level gauge comprising a reference reflector, the reference reflector being arranged at a known reference reflector level, wherein the method comprises the steps of: transmitting a plurality of electromagnetic transmit signals towards a surface of said product in the tank;receiving a plurality of electromagnetic reflection signals, each including several echoes resulting from reflection of a corresponding one of said electromagnetic transmit signals at impedance discontinuities encountered by the electromagnetic transmit signal;determining a first verification level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at said reference reflector;determining a second verification level based on a surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product; anddetermining a test result based on a relation between said first verification level and said known reference reflector level, and on said second verification level,wherein the method further comprises the steps of: determining an amplitude of said reference reflector echo; anddetermining an amplitude of said surface echo,wherein said test result is determined to be positive only if: said amplitude of the surface echo is greater than said amplitude of the reference reflector echo. 32. A method for testing a radar level gauge arranged at a tank containing a product, said radar level gauge comprising a reference reflector, the reference reflector being arranged at a known reference reflector level at or above a high level alarm limit for said tank, wherein the method comprises the steps of: transmitting a plurality of electromagnetic transmit signals towards a surface of said product in the tank;receiving a plurality of electromagnetic reflection signals, each including several echoes resulting from reflection of a corresponding one of said electromagnetic transmit signals at impedance discontinuities encountered by the electromagnetic transmit signal;determining a proof test filling level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at the reference reflector; andproviding, to a host system externally of said radar level gauge, a signal indicative of the proof test filling level,wherein said radar level gauge is further controllable to operate in a filling level measuring state or a system proof test state, said method further comprising the steps of: determining in said radar level gauge a filling level of said product based on a surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product;providing from said radar level gauge a signal indicative of said filling level to said host system;receiving, as an input to said radar level gauge, a system proof test start command;controlling, in response to said system proof test start command, said radar level gauge to enter said proof test state; andcontrolling, after having provided to said host system said signal indicative of the proof test filling level, said radar level gauge to exit said system proof test state,wherein the method further comprises the steps of: determining the proof test filling level while said radar level gauge is in said proof test state; andcontrolling, if a difference between said proof test filling level and said high level alarm limit is smaller than a threshold value, said radar level gauge back to said filling level measuring state. 33. A filling level measuring system comprising a host system and a radar level gauge coupled to said host system, for determining a filling level of a product in a tank, said radar level gauge comprising: a transceiver for generating, transmitting and receiving electromagnetic signals;a reference reflector arranged at a known reference reflector level at or above a high level alarm limit for said tank;a propagating device connected to said transceiver and arranged to propagate a plurality of electromagnetic transmit signals from said transceiver towards said product in the tank, and to return to said transceiver a plurality of electromagnetic reflection signals, each including several echoes resulting from reflection of a corresponding one of said electromagnetic transmit signals at impedance discontinuities encountered by the electromagnetic transmit signal; andprocessing circuitry for determining said filling level based on a surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product,wherein said radar level gauge is controllable between a filling level measuring state and a proof test state,wherein, in said proof test state, said processing circuitry is configured to: determine a proof test filling level based on a reference reflector echo resulting from reflection of one of said electromagnetic transmit signals at the reference reflector; andprovide, to said host system, a signal indicative of the proof test filling level,wherein, in said filling level measuring state, said processing circuitry is configured to: determine the filling level of said product based on said surface echo resulting from reflection of one of said electromagnetic transmit signals at said surface of the product;provide a signal indicative of said filling level to said host system;receive, as an input to said radar level gauge, a system proof test start command;control, in response to said system proof test start command, said radar level gauge to enter said proof test state; anddetermine the proof test filling level while said radar level gauge is in said proof test state,wherein said host system is configured to control said radar level gauge back to said filling level measuring state, if a difference between said proof test filling level and said high level alarm limit is smaller than a threshold value. 34. The filling level system according to claim 33, wherein said reference reflector is attached to said propagation device. 35. The filling level measurement system according to claim 33, wherein said propagating device is a transmission line probe. 36. The filling level measuring system according to claim 35, wherein said reference reflector comprises: a first and a second part arranged to together substantially surround said transmission line probe; andat least one releasable fastener arranged to join said first part to said second part in such a way that said transmission line probe is clamped between said first part and said second part. 37. The filling level measuring according to claim 36, wherein said reference reflector comprises a first releasable fastener on a first side of said transmission line probe and a second releasable fastener on a second side of said transmission line probe opposite said first side,said second releasable fastener being offset relative to said first releasable fastener in a direction parallel to a longitudinal extension of said transmission line probe. 38. The filling level measuring according to claim 37, wherein said first releasable fastener and said second releasable include screws, the heads of which face the same way when the reference reflector is assembled. 39. The filling level measuring according to claim 33, wherein said propagating device is a radiating antenna. 40. The filling level measuring system according to claim 39, wherein said radiating antenna is selected from a set including a parabolic antenna, a horn antenna, and a still pipe feeder antenna, wherein said radiating antenna has a reference reflector attachment for mounting a reference reflector assembly, said reference reflector assembly including an elongated and laterally flexible suspension member coupled at an upper end to said reference reflector attachment and coupled at a lower end to a reflector surface having drip-off properties and to a weight for orientation of said reflector surface, wherein a distance between said radiating antenna and said reference reflector surface is adjustable. 41. The filling level measuring system according to claim 33, further comprising an additional filling level measuring device arranged to measure the filling level of the product in said tank.
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