Radar level gauge system and method for reduced lower dead zone

Patent metadata

Field	Value
Publication number	US-11933655-B2
Application number	US-202117516895-A
Country	US
Kind code	B2
Filing date	Nov 2, 2021
Priority date	Dec 3, 2020
Publication date	Mar 19, 2024
Grant date	Mar 19, 2024

Abstract

In summary, the present invention thus relates to a method of determining a level of a product in a tank, comprising generating and transmitting an electromagnetic transmit signal; guiding the transmit signal towards and into the product; returning an electromagnetic reflection signal resulting from reflection of the transmit signal; receiving, the reflection signal; determining, based on the reflection signal and a timing relation between the reflection signal and the transmit signal, an echo signal exhibiting an echo signal strength as a function of a propagation parameter indicative of position along the probe; and determining the level of the surface of the product based on a propagation parameter value indicative of a first threshold position along the probe for which the echo signal has reached a predetermined threshold signal strength, and an offset indicative of an offset distance along the probe from the first threshold position towards the second probe end.

First claim

The invention claimed is:

1. A method of determining a level of a product in a tank, using a radar level gauge system comprising:
a transceiver;
a probe arranged to extend towards and into the product from a first probe end coupled to the transceiver to a second probe end, the probe comprising a first probe conductor and a second probe conductor being conductively coupled to each other by a probe termination arrangement at the second probe end; and
processing circuitry,
the method comprising the steps of:
generating and transmitting, by the transceiver, an electromagnetic transmit signal;
guiding, by the probe, the transmit signal towards and into the product;
returning, by the probe, an electromagnetic reflection signal resulting from reflection of the transmit signal at the surface of the product and at the second probe end;
receiving, by the transceiver, the reflection signal;
determining, based on the reflection signal and a timing relation between the reflection signal and the transmit signal, an echo signal exhibiting an echo signal strength as a function of a propagation parameter indicative of position along the probe; and
determining, by the processing circuitry, the level of the surface of the product based on a propagation parameter value indicative of a first threshold position along the probe for which the echo signal has reached a predetermined threshold signal strength, and an offset indicative of an offset distance along the probe from the first threshold position towards the second probe end.

2. The method according to claim 1 , further comprising the step of:
receiving a temperature parameter value indicative of a present temperature in the tank; and
determining the offset based on the present temperature.

3. The method according to claim 1 , wherein the offset is based on at least one material property of the product.

4. The method according to claim 1 , wherein the offset is based on at least one previously determined echo signal.

5. The method according to claim 1 , wherein:
the transmit signal comprises a first pulse train having a first pulse repetition frequency; and
the method further comprises the steps of:
generating, by the transceiver, an electromagnetic reference signal in the form of a second pulse train having a second pulse repetition frequency controlled to differ from the first pulse repetition frequency by a frequency difference; and
the echo signal is determined based on the reflection signal, the reference signal, and the frequency difference.

6. A radar level gauge system for determining a level of a product in a tank, the radar level gauge system comprising:
a transceiver for generating, transmitting and receiving electromagnetic signals;
a probe arranged to extend towards and into the product from a first probe end coupled to the transceiver to a second probe end, the probe comprising a first probe conductor and a second probe conductor being conductively coupled to each other by a probe termination arrangement at the second probe end;
echo signal forming circuitry connected to the transceiver for forming, based on the reflection signal and a timing relation between the reflection signal and the transmit signal, an echo signal exhibiting an echo signal strength as a function of a propagation parameter indicative of position along the probe; and
level determining circuitry connected to the echo signal forming circuitry for determining the level of the product in the tank based on a propagation parameter value indicative of a first threshold position along the probe for which the echo signal has reached a predetermined threshold signal strength, and an offset indicative of an offset distance along the probe from the first threshold position towards the second probe end.

7. The radar level gauge system according to claim 6 , wherein the probe termination arrangement provides an inductance between the first probe conductor and the second probe conductor being higher than 1 nH.

8. The radar level gauge system according to claim 7 , wherein the probe termination arrangement provides an inductance between the first probe conductor and the second probe conductor being lower than 30 nH.

9. The radar level gauge system according to claim 6 , wherein the probe termination arrangement comprises an electrically conductive member attached to the first probe conductor and to the second probe conductor.

10. The radar level gauge system according to claim 9 , wherein the electrically conductive member is conductively and mechanically connected to the first probe conductor and to the second probe conductor by at least one of welding, screwing, riveting and spring forces.

11. The radar level gauge system according to claim 9 , wherein the electrically conductive member has an extension of at least 10 mm in a longitudinal direction of the probe.

12. The radar level gauge system according to claim 6 , wherein the probe is a coaxial probe having an inner conductor and an outer conductor.

13. The radar level gauge system according to claim 6 , wherein:
the radar level gauge system further comprises temperature indicating circuitry for indicating a temperature parameter value indicative of a present temperature in the tank; and
the level determining circuitry is further configured to determining the first offset based on the temperature parameter value.

14. The radar level gauge system according to claim 6 , wherein:
the transceiver comprises:
transmission signal generating circuitry for generating the transmit signal in the form of a first pulse train having a first pulse repetition frequency; and
reference signal generating circuitry for generating an electromagnetic reference signal in the form of a second pulse train having a second pulse repetition frequency controlled to differ from the first pulse repetition frequency by a frequency difference; and
the echo signal forming circuitry is configured to form the echo signal based on the reflection signal, the reference signal, and the frequency difference.

Assignees

• Rosemount Tank Radar Ab

Inventors

• Eriksson Mikael
• Hjorth Johannes
• Söderström Jimmie

Classifications

• G01F23/284 Primary

  Electromagnetic waves · CPC title

• G01S7/2922

  by using a controlled threshold · 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

• G01S7/411

  Identification of targets based on measurements of radar reflectivity (G01S7/415 takes precedence) · CPC title

• G01S7/28

  Details of pulse systems · CPC title