Floatless pulsed wave guide liquid level measurement

Patent metadata

Field	Value
Publication number	US-10054476-B2
Application number	US-201514792685-A
Country	US
Kind code	B2
Filing date	Jul 7, 2015
Priority date	Jul 7, 2014
Publication date	Aug 21, 2018
Grant date	Aug 21, 2018

Abstract

A waveguide arrangement may include a tank defining a chamber for holding a liquid; and a pulsed waveguide (PWG) disposed at least partially within the chamber, the PWG comprising: an inner cylinder, the inner cylinder being grounded. The waveguide may also include an electrically conductive coil wrapped around the inner cylinder, wherein the pulsed waveguide is arranged to generate a first delay between a first initial pulse and a first reflected pulse when an upper surface of the liquid is at a first level, and to generate a second delay between a second initial pulse and a second reflected pulse when the upper surface of the liquid is a second level.

First claim

What is claimed is:

1. A waveguide arrangement, comprising
a tank defining a chamber for holding a liquid; and
a pulsed waveguide (PWG) disposed at least partially within the chamber, the PWG comprising:
an inner cylinder, the inner cylinder being grounded;
an electrically conductive coil wrapped around the inner cylinder, wherein the pulsed waveguide is arranged to generate a first delay between a first initial pulse and a first reflected pulse when an upper surface of the liquid is at a first level, and to generate a second delay between a second initial pulse and a second reflected pulse when the upper surface of the liquid is a second level;
and an electronics module configured to determine a change in the level of the fluid surface based on the first delay and the second delay.

2. The waveguide arrangement of claim 1 , further comprising a ground cylinder disposed around the inner cylinder.

3. The waveguide arrangement of claim 1 , wherein the inner cylinder, ground cylinder, and electrically conductive coil comprise stainless steel.

4. The waveguide arrangement of claim 1 , further comprising an electrical insulator disposed between the inner cylinder and electrically conductive coil.

5. The waveguide arrangement of claim 4 , wherein the electrical insulator comprises a plurality of rods having a rod axis parallel to a cylinder axis of the inner cylinder.

6. The waveguide arrangement of claim 1 , wherein the electrically conductive coil has a first end and a second end, the waveguide arrangement further comprising an electrically conductive branch coupled to a select winding of the electrically conductive coil between the first end and the second end, the electrically conductive branch arranged to transmit a reference signal when the first initial pulse reaches the branch.

7. The waveguide arrangement of claim 6 , wherein the coil comprises:
a first portion disposed between the first end and the electrically conductive branch, the first portion having a first pitch between adjacent windings of the first portion; and
a second portion disposed between the electrically conductive branch and the second end, the second portion having a second pitch different than the first pitch between adjacent windings of the second portion.

8. The waveguide arrangement of claim 1 , wherein a terminal end of the electrically conductive coil has a high impedance to ground, the pulsed waveguide arranged to:
generate a reflected pulse at a liquid surface in response to a given initial pulse, wherein a polarity of the reflected pulse is different than a polarity of the initial pulse; and
generate an empty tank reflection in response to the given initial pulse, wherein a polarity of the empty tank reflection matches the polarity of the initial pulse.

9. A level sensing system configured to measure a level of a liquid comprising:
a tank for holding the liquid;
a pulsed waveguide (PWG) disposed at least partially within the tank, the PWG having an inner cylinder and an electrically conductive coil wrapped about the inner cylinder; and
an electronics module configured to transmit an initial pulse to the PWG and receive a reflected pulse from the PWG, wherein the reflection is caused by either (i) a change in impedance or permittivity between the liquid and an adjacent medium or (ii) a low impedance path to ground, wherein the electrically conductive coil has a first end and a second end, the PWG further comprising an electrically conductive branch coupled to a select winding of the electrically conductive coil between the first end and the second end, the electrically conductive branch arranged to transmit a reference signal when the initial pulse reaches the branch, wherein the electrically conductive coil comprises:
a first portion disposed between the first end and the electrically conductive branch, the first portion having a first pitch between adjacent windings of the first portion; and
a second portion disposed between the electrically conductive branch and the second end, the second portion having a second pitch different than the first pitch between adjacent windings of the second portion.

10. The level sensing system of claim 9 , wherein the electronics module comprises a pulse generator to generate the initial pulse, a signal receiver to receive the reflected pulse, and a level determination module to determine the level of the liquid based upon a timing of the initial pulse and the reflected pulse.

11. The level sensing system of claim 9 , wherein the PWG is arranged to generate a first delay between a first initial pulse and a first reflected pulse when an upper surface of the liquid is at a first level, and to generated a second delay between a second initial pulse and a second reflected pulse when the upper surface of the liquid is a second level.

12. The level sensing system of claim 9 , further comprising a ground cylinder disposed around the inner cylinder, wherein the inner cylinder, ground cylinder, and electrically conductive coil comprise stainless steel.

13. The level sensing system of claim 9 , further comprising an electrical insulator disposed between the inner cylinder and electrically conductive coil.

Assignees

• Littelfuse Inc

Inventors

• Johnson Brian
• Fesshaie Efrem
• Misevicius Rimantas

Classifications

• G01F23/284 Primary

  Electromagnetic waves · CPC title