RADAR LEVEL GAUGE SYSTEM AND METHOD PROVIDING A SIGNAL INDICATIVE OF PROCESS RELIABILITY

• US 20090146867A1
• Filed: 12/06/2007
• Published: 06/11/2009
• Est. Priority Date: 12/06/2007
• Status: Active Grant

• Current Assignee: Rosemount Tank Radar AB (Emerson Electric Company)
• Original Assignee: Rosemount Tank Radar AB (Emerson Electric Company)
• Inventors: Karlsson, Per, Delin, Hakan
• Granted Patent: US 7,551,122 B1
• Time in Patent Office: Days
• US Class Current: 342/124
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G01F 25/20 of apparatus for measuring liquid level

Abstract

A method for determination of a filling level of a product contained in a tank, comprising the steps of generating and transmitting an electromagnetic signal; propagating the transmitted electromagnetic signal towards the product in the tank; receiving echo signals resulting from reflections at impedance transitions encountered by the transmitted electromagnetic signal; classifying one of the echo signals as a surface echo signal resulting from reflection at a surface of the product inside the tank; evaluating an additional echo signal; providing, if an amplitude of the additional echo signal is greater than a predetermined disturbance echo threshold, a signal indicative thereof; and determining the filling level based on the surface echo signal.

Claims

1. A method for determination of a filling level of a product contained in a tank, comprising the steps of:

generating and transmitting an electromagnetic signal;

propagating said transmitted electromagnetic signal towards said product in the tank;

receiving echo signals resulting from reflections at impedance transitions encountered by said transmitted electromagnetic signal;

classifying one of said echo signals as a surface echo signal resulting from reflection at a surface of said product inside the tank;

evaluating an additional echo signal;

providing, if an amplitude of said additional echo signal is greater than a predetermined disturbance echo threshold, a signal indicative thereof; and

determining said filling level based on said surface echo signal.

2. The method according to claim 1, wherein said signal is provided only if said additional echo signal results from reflection at an impedance transition located above a position associated with said surface echo signal.

3. The method according to claim 1, wherein a first received echo signal having an amplitude greater than a predetermined surface echo threshold is classified as said surface echo signal.

4. The method according to claim 3, wherein said disturbance echo threshold is a predetermined fraction of said surface echo threshold.

5. The method according to claim 1, farther comprising the step of:

determining a speed of an impedance transition, based on echo signals that result from reflection at said impedance transition and are received at different points in time.

6. The method according to claim 1, further comprising the steps of:

determining a speed of a first impedance transition reflecting an echo signal having an amplitude greater than said disturbance echo threshold;

determining a speed of a second impedance transition classified as said surface of the product inside the tank; and

if said speed of the first impedance transition is higher than said speed of the second impedance transition, provide a signal indicative thereof.

7. The method according to claim 6, wherein said signal is provided only if the speed of the second impedance transition is lower than 10⁻

5 m/s and the speed of the first impedance transition is higher than ten times 10<sup>−

5</sup> m/s.

8. The method according to claim 1, wherein said transmitted electromagnetic signal is propagated towards said product using a probe arranged to extend into said product and configured to guide electromagnetic signals.

9. The method according to claim 8, wherein said impedance transitions encountered by said transmitted electromagnetic signal are present along said probe, and said predetermined disturbance echo threshold is a probe contamination threshold.

10. The method according to claim 9, wherein said probe contamination threshold is related to a baseline representing electromagnetic signals guided towards said transceiver by the probe when uncontaminated.

11. A radar level gauge system, for determination of a filling level of a product contained in a tank, said radar level gauge system comprising:

a transceiver for generating, transmitting and receiving electromagnetic signals;

a propagation device connected to said transceiver and arranged to propagate a transmitted electromagnetic signal towards said product inside the tank, and to return echo signals resulting from reflections at impedance transitions encountered by said transmitted signal back to said transceiver; and

processing circuitry connected to said transceiver and comprising;

a signal classifier for classifying one of said echo signals as a surface echo signal resulting from reflection at a surface of said product inside the tank;

a comparator for comparing an amplitude of an additional echo signal with a disturbance echo threshold;

a signal generator for providing, if said amplitude is greater than said disturbance echo threshold, a signal indicative thereof; and

determination circuitry for determining said filling level based on said surface echo signal.

12. The radar level gauge system according to claim 11, wherein said additional echo signal results from reflection at an impedance transition located above a position associated with said surface echo signal.

13. The radar level gauge system according to claim 11, wherein said echo signal classified as said surface echo signal is the first received echo signal having an amplitude greater than a predetermined surface echo threshold.

14. The radar level gauge system according to claim 13, wherein said probe contamination threshold is a predetermined fraction of said surface echo threshold.

15. The radar level gauge system according to claim 11, further comprising storage means for storing position data for an impedance transition based on echo signals that result from reflection at said impedance transition and are received at different points in time, thereby enabling determination of a speed of said impedance transition.

16. The radar level gauge system according to claim 11, wherein said propagation device is a probe arranged to extend into said product and configured to guide electromagnetic signals.

17. A method for determination of a filling level of a product contained in a tank, comprising the steps of:

generating and transmitting an electromagnetic signal using a transceiver;

propagating said transmitted electromagnetic signal towards said product in the tank;

receiving echo signals resulting from reflections at impedance transitions encountered by said transmitted electromagnetic signal;

classifying one of said received echo signals as a surface echo signal resulting from reflection at a surface of said product inside the tank;

evaluating an additional echo signal resulting from reflection at an additional impedance transition located above a position associated with said surface echo signal;

determining a reliability measure for said determination of the filling level based on at least one property of said additional echo signal; and

determining said filling level based on said surface echo signal.

18. The method according to claim 17, wherein said additional echo signal has a larger amplitude than any other echo signal resulting from reflection at an impedance transition located above a position associated with said surface echo signal and has the same sign as said surface echo signal.

19. The method according to claim 17, wherein said reliability measure is based on a relation between said additional echo signal and said surface echo signal.

20. The method according to claim 19, wherein said reliability measure is based on a ratio between said surface echo signal and a sum of said additional echo signal and an offset value.

21. The method according to claim 17, wherein.

said surface echo signal is classified as such by comparing said echo signals with a surface echo threshold;

and

said reliability measure is determined based on a relation between said additional echo signal and said surface echo threshold

22. The method according to claim 21, wherein said reliability measure is based on a ratio between said surface echo threshold and a sum of said additional echo signal and an offset value.

23. The method according to claim 19, wherein said reliability measure is additionally based on a relation between said surface echo signal and said surface echo threshold.

24. The method according to claim 20, wherein said reliability measure is additionally based on a ratio between said surface echo signal and a sum of said surface echo threshold and an offset value.

25. The method according to claim 21, wherein said reliability measure is additionally based on a relation between said surface echo signal and said surface echo threshold.

26. The method according to claim 22, wherein said reliability measure is additionally based on a ratio between said surface echo signal and a sum of said surface echo threshold and an offset value.

27. The method according to claim 17, wherein said transmitted electromagnetic signal is propagated towards said product using a probe arranged to extend into said product and configured to guide electromagnetic signals.

28. A radar level gauge system, for determination of a filling level of a product contained in a tank, said radar level gauge system comprising:

a transceiver for generating, transmitting and receiving electromagnetic signals;

a propagation device connected to said transceiver and arranged to propagate a transmitted electromagnetic signal from said transceiver towards said product inside the tank, and to return echo signals resulting from reflections of said transmitted electromagnetic signal at impedance transitions encountered by said transmitted electromagnetic signal back to said transceiver; and

processing circuitry connected to said transceiver and comprising;

a signal classifier for classifying one of said echo signals as a surface echo signal resulting from reflection at a surface of said product inside the tank;

an evaluator for evaluating an additional echo signal; and

determination circuitry for determining a reliability measure for said determination of the filling level based on at least one property of said additional echo signal and for determining said filling level based on said surface echo signal.

29. The radar level gauge system according to claim 28, wherein said additional echo signal has a larger amplitude than any other echo signal resulting from reflection at an impedance transition located above a position associated with said surface echo signal and has the same sign as said surface echo signal.

30. The radar level gauge system according to claim 28, wherein said reliability measure is based on a relation between said additional echo signal and said surface echo signal.

31. The radar level gauge system according to claim 30, wherein said reliability measure is based on a ratio between said surface echo signal and a sum of said additional echo signal and an offset value.

32. The radar level gauge system according to claim 28, wherein:

said surface echo signal is classified as such by comparing said echo signals with a surface echo threshold; and

said reliability measure is determined based on a relation between said additional echo signal and said surface echo threshold.

33. The radar level gauge system according to claim 32, wherein said reliability measure is based on a ratio between said surface echo threshold and a sum of said additional echo signal and an offset value.

34. The radar level gauge system according to claim 30, wherein said reliability measure is additionally based on a relation between said surface echo signal and said surface echo threshold.

35. The radar level gauge system according to claim 31, wherein said reliability measure is additionally based on a ratio between said surface echo signal and a sum of said surface echo threshold and an offset value.

36. The radar level gauge system according to claim 32, wherein said reliability measure is additionally based on a relation between said surface echo signal and said surface echo threshold.

37. The radar level gauge system according to claim 32, wherein said reliability measure is additionally based on a ratio between said surface echo signal and a sum of said surface echo threshold and an offset value.

38. The radar level gauge system according to claim 28, wherein said transmitted electromagnetic signal is propagated towards said product using a probe arranged to extend into said product and configured to guide electromagnetic signals.

39. A method for determination of a filling level of a product contained in a tank, comprising the steps of:

generating and transmitting an electromagnetic signal using a transceiver;

propagating said transmitted electromagnetic signal towards said product in the tank;

receiving echo signals resulting from reflections at impedance transitions encountered by said transmitted electromagnetic signal;

classifying one of said received echo signals as a surface echo signal resulting from reflection at a surface of said product inside the tank;

evaluating an additional echo signal resulting from reflection at an additional impedance transition located above a position associated with said surface echo signal;

determining a reliability measure for said determination of the filling level based on a relation between said surface echo signal and said surface echo threshold; and

determining said filling level based on said surface echo signal.

40. The method according to claim 39, wherein said transmitted electromagnetic signal is propagated towards said product using a probe arranged to extend into said product and configured to guide electromagnetic signals.

101-140. -140. (canceled)