Method for determining quality of measurement in a radar level gauge system

1. A method for determining a quality of measurement in a radar level gauge system arranged to measure a filling level of a content contained in a tank, comprising the steps of:

providing an antenna having at least two separate antenna functions, including a transmitting function and a receiving function;

transmitting microwave energy using said transmitting function of said antenna;

receiving a reflected part of said microwave energy, reflected from said level of content to be gauged, using said receiving function of said antenna;

detecting a leakage signal, said leakage signal leaking from said transmitting function of said antenna to said receiving function of said antenna; and

determining, based on a variation in a relationship between said leakage signal and said reflected signal over time, a level of quality of said reflected signal.

2. A method according to claim 1 , wherein said steps of transmitting, receiving, detecting and determining are performed continuously over time.

3. A method according to claim 1 , wherein a time between execution of said steps of receiving and detecting is less than 2 hours, more preferably less than 30 minutes and most preferably less than 60 seconds.

4. A method according to claim 1 , wherein said step of determining comprises the steps of:

calculating a quotient between said leakage signal and said reflected signal; and

comparing said quotient with a pre-determined allowable quality measurement range, wherein an alarm is produced if said quotient goes outside said allowable quality measurement range.

5. A method according to claim 1 , wherein said step of determining comprises the steps of:

calculating a variation over time based on a quotient between said leakage signal and said reflected signal; and

comparing said variation over time with a pre-determined allowable quality measurement range,

wherein an alarm is produced if said variation over time goes outside said allowable quality measurement range.

6. A method according to claim 4 , wherein said step of calculating a quotient between said leakage signal and said reflected signal is calculated using absolute values of said signals.

7. A method according to claim 1 , wherein said antenna is one of a horn antenna, a reflector mirror antenna, a dielectric rod antenna, and an array antenna.

8. A method according to claim 1 , wherein said antenna is covered by a material resistant to corrosivity, selected from a group comprising fluoroplastic materials, PTFE, PPS, PEEK, FEP, PFA, HALAR and Metalon.

9. A method according to claim 1 , wherein in said step of detecting the leakage signal, the phase information of the transmitted and received microwave energy is further considered.

10. A method for measuring a filling level of a content contained in a tank, comprising the steps of:

providing an antenna having at least two antenna functions, including a transmitting function and a receiving function;

transmitting microwave energy using said transmitting function of said antenna;

receiving a reflected part of said microwave energy, reflected from said level of content to be gauged, using said receiving function of said antenna;

calculating a level of content in said tank based on said reflected signal;

detecting a leakage signal, said leakage signal leaking from said transmitting function of the antenna to said receiving function of the antenna; and

determining, based on a variation in a relationship between said leakage signal and said reflected signal over time, a level of quality of said calculation.

11. A method according to claim 10 , wherein at least said steps of transmitting, receiving, detecting and determining are performed continuously over time.

12. A method according to claim 10 , wherein a time between execution of said steps of receiving and detecting is less than 2 hours, more preferably less than 30 minutes and most preferably less than 60 seconds.

13. A method according to claim 10 , wherein said step of determining comprises the steps of:

calculating a quotient between said leakage signal and said reflected signal; and

comparing said quotient with a pre-determined allowable quality measurement range, wherein an alarm is produced if said quotient goes outside said allowable quality measurement range.

14. A method according to claim 10 , wherein said step of determining comprises the steps of:

calculating a variation over time based on a quotient between said leakage signal and said reflected signal; and

comparing said variation over time with a pre-determined allowable quality measurement range,

wherein an alarm is produced if said variation over time goes outside said allowable quality measurement range.

15. A method according to claim 13 , wherein said step of calculating a quotient between said leakage signal and said reflected signal is calculated using absolute values of said signals.

16. A method according to claim 10 , wherein said antenna is one of a horn antenna, a reflector mirror antenna, a dielectric rod antenna, and an array antenna.

17. A method according to claim 10 , wherein said antenna is covered by a material resistant to corrosivity, selected from a group comprising fluoroplastic materials, PTFE, PPS, PEEK, FEP, PFA, HALAR and Metalon.

18. A method according to claim 10 , wherein in said step of detecting the leakage signal, the phase information of the transmitted and received microwave energy is further considered.

19. A radar level gauge system, for measuring a filling level of a content contained in a tank, said radar level gauge system comprising:

an antenna having at least two antenna functions, including a transmitting function and a receiving function;

a transmitter arranged outside said tank and configured to transmit microwave energy using a transmitting function of said antenna;

a receiver arranged outside said tank and configured to receive reflected microwave energy, reflected from said level of content to be gauged, using a receiving function of said antenna; and

a controller arranged to determining a filling level based on said reflected microwave energy;

wherein the controller is further arranged to detect a leakage signal, said leakage signal leaking from said transmitting function of said antenna to said receiving function of said antenna and to determine, based on a variation in a relationship between said leakage signal and said reflected signal over time, a level of quality of said reflected signal.

20. A radar level gauge system according to claim 19 , wherein said system is arranged to continuously over time perform said quality measurement determination.

21. A radar level gauge system according to claim 19 , wherein a time between execution of said steps of receiving and detecting is less than 2 hours, more preferably less than 30 minutes and most preferably less than 60 seconds.

22. A radar level gauge system according to claim 19 , wherein said controller is further arranged to:

calculate a quotient between said leakage signal and said reflected signal; and

comparing said quotient with a pre-determined allowable quality measurement range,

wherein an alarm is produced if said quotient goes outside said allowable quality measurement range.

23. A radar level gauge system according to claim 19 , wherein said controller is further arranged to:

calculate a variation over time based on a quotient between said leakage signal and said reflected signal; and

comparing said variation over time with a pre-determined allowable quality measurement range,

wherein an alarm is produced if said variation over time goes outside said allowable quality measurement range.

24. A radar level gauge system according to claim 22 , wherein said quotient between said leakage signal and said reflected signal is calculated using absolute values of said signals.

25. A radar level gauge system according to claim 19 , wherein said antenna is one of a horn antenna, a reflector mirror antenna, a dielectric rod antenna, and an array antenna.

26. A radar level gauge system according to claim 19 , wherein said antenna is covered by a material resistant to corrosivity, selected from a group comprising fluoroplastic materials, PTFE, PPS, PEEK, FEP, PFA, HALAR and Metalon.