Guided wave radar level gauge system for interface measurement

Patent metadata

Field	Value
Publication number	US-10184820-B2
Application number	US-201615281341-A
Country	US
Kind code	B2
Filing date	Sep 30, 2016
Priority date	Sep 30, 2016
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

A radar level gauge system comprising: a transceiver; a tank feed-through; a power divider to divide a transmit signal into a first transmit signal and a second transmit signal; a first probe member configured to guide the first transmit signal and to return a first reflection signal, said first probe member providing a first relatively large average attenuation; a second probe member configured to guide said second transmit signal and to return a second reflection signal, said second probe member providing a second relatively small average attenuation; measurement signal forming circuitry for forming a measurement signal comprising a first set of echo indicators indicating reflection of said first transmit signal, and a second set of echo indicators indicating reflection of said second transmit signal; and level determining circuitry for determining a first level based on said first set of echo indicators, and a second, deeper, level based on said second set of echo indicators.

First claim

What is claimed is:

1. A radar level gauge system for installation at a tank containing a stratified substance composition including at least a first substance having a first density, a second substance having a second density greater than said first density, and a third substance having a third density greater than said second density, to determine a first level of a first interface between said first substance and said second substance, and a second level of a second interface between said second substance and said third substance, said radar level gauge system comprising:
a transceiver for generating and transmitting an electromagnetic transmit signal, and receiving an electromagnetic reflection signal;
a tank feed-through connected to said transceiver;
a power divider connected to said feed-through to divide the transmit signal from said transceiver into a first transmit signal and a second transmit signal, and to combine a first reflection signal and a second reflection signal to the reflection signal received by said transceiver;
a first transmission line probe member having an upper end connected to said power divider and being configured to guide the first transmit signal at least partly through said stratified substance composition towards a lower end of said first transmission probe member and to return said first reflection signal resulting from reflection of said first transmit signal at any impedance discontinuities encountered thereby, said first transmission line probe member being configured to provide an interaction between said first transmit signal and said stratified substance composition resulting in a first relatively large average attenuation of said first transmit signal;
a second transmission line probe member having an upper end connected to said power divider and configured to guide said second transmit signal at least partly through said stratified substance composition towards a lower end of said second transmission probe member and to return said second reflection signal resulting from reflection of said second transmit signal at any impedance discontinuities encountered thereby, said second transmission line probe member being configured to provide an interaction between said second transmit signal and said stratified substance composition resulting in a second relatively small average attenuation of said second transmit signal;
measurement signal forming circuitry connected to said transceiver for forming a measurement signal based on said reflection signal and a timing relation between said transmit signal and said reflection signal, said measurement signal comprising a first set of echo indicators indicating reflection of said first transmit signal at impedance discontinuities encountered by said first transmit signal, and a second set of echo indicators indicating reflection of said second transmit signal at impedance discontinuities encountered by said second transmit signal; and
level determining circuitry for determining said first level based on at least one echo indicator from said first set of echo indicators, and determining said second level based on at least one echo indicator from said second set of echo indicators.

2. The radar level gauge system according to claim 1 , wherein said second transmission line probe member comprises:
a probe conductor connected to said power divider; and
a first dielectric layer at least partly enclosing said probe conductor.

3. The radar level gauge system according to claim 2 , wherein said first dielectric layer is configured to provide different coupling between said second transmit signal and a given surrounding medium at different positions along said second transmission line probe member.

4. The radar level gauge system according to claim 3 , wherein said second dielectric layer is configured to provide a decreasing coupling between said second transmit signal and said given surrounding medium with increasing distance from said power divider.

5. The radar level gauge system according to claim 2 , wherein said first transmission line probe member comprises:
a probe conductor connected to said power divider; and
a second dielectric layer, different from the first dielectric layer comprised in said second transmission line probe member, at least partly enclosing said probe conductor.

6. The radar level gauge system according to claim 5 , wherein said second dielectric layer is configured to provide different coupling between said first transmit signal and a given surrounding medium at different positions along said first transmission line probe member.

7. The radar level gauge system according to claim 6 , wherein said first dielectric layer is configured to provide a decreasing coupling between said first transmit signal and said given surrounding medium with increasing distance from said power divider.

8. The radar level gauge system according to claim 1 , wherein said second transmission line probe member comprises:
a probe conductor connected to said power divider; and
a shielding conductor spaced apart from said probe conductor and extending along at least a portion of said second transmission line probe member.

9. The radar level gauge system according to claim 8 , wherein said shielding conductor extends along at least said portion of said second transmission line probe starting from the upper end of said second transmission line probe member.

10. The radar level gauge system according to claim 1 , wherein:
said first transmission line probe comprises a first probe conductor conductively connected to said power divider to receive said first transmit signal, and a shielding conductor extending along at least a portion of said first probe conductor; and
said second transmission line probe comprises a second probe conductor conductively connected to said power divider to receive said second transmit signal, and said shielding conductor extending along at least a portion of said first probe conductor and said second probe conductor.

11. The radar level gauge system according to claim 10 , wherein said shielding conductor is configured to provide different coupling between at least one of said first transmit signal and said second transmit signal, and a given surrounding medium at different vertical positions in said tank.

12. The radar level gauge system according to claim 1 , wherein:
said first transmission line probe member comprises a probe conductor connected to said power divider;
said second transmission line probe member comprises a probe conductor connected to said power divider; and
the probe conductor of said first transmission line probe member is conductively connected to the probe conductor of said second transmission line probe member at the lower ends of said first transmission line probe member and said second transmission line probe member.

13. The radar level gauge system according to claim 12 , wherein the probe conductor of said first transmission line probe member is conductively connected to the probe conductor of said second transmission line probe member at the lower ends of said first transmission line probe member and said second transmission line probe member through a delay line for increasing a temporal separation between said first reflection signal and said second reflection signal.

14. The radar level gauge system according to claim 12 , wherein said second transmission line probe member comprises a shielding conductor spaced apart from said probe conductor and extending along at least a portion of said second transmission line probe member.

15. The radar level gauge system according to clai

Assignees

• Rosemount Tank Radar Ab

Inventors

• Edvardsson Olov
• Eriksson Mikael
• Larsson Michael

Classifications

• G01F23/284 Primary

  Electromagnetic waves · CPC title

• G01S13/88

  Radar or analogous systems specially adapted for specific applications (electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00) · CPC title

• G01S7/28

  Details of pulse systems · CPC title

• G01S7/03

  Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver · CPC title

• G01S7/282

  Transmitters · CPC title