Ludion pressure measurement system

Patent metadata

Field	Value
Publication number	US-11385116-B2
Application number	US-202017032136-A
Country	US
Kind code	B2
Filing date	Sep 25, 2020
Priority date	Sep 25, 2019
Publication date	Jul 12, 2022
Grant date	Jul 12, 2022

Abstract

Systems and methods for pressure measurement are provided. A ludion with a trapped gas bubble floats between two liquids. Pressure acting upon the liquids causes the bubble to expand or contract, resulting in movement of the ludion which can be measured and correlated with pressure change. Pressure measuring device can measure pressures from 0.05 inHg to 110 inHg with a four-to-one Test Accuracy Ratio (TAR) without using mercury.

First claim

What is claimed is:

1. A pressure measurement system comprising:
a first container;
a first liquid disposed within the first container;
a second liquid disposed within the first container; and
a second container formed with a cavity and an aperture, wherein the second container is disposed within the first container;
wherein the cavity opens to an exterior of the second container through the aperture;
wherein a gas is disposed within the cavity such that the gas is trapped within the second container by pressure; and
wherein the second container includes a reflective section on an outer surface of the second container, the reflective section comprising a reflector configured to reflect laser light such that a laser interferometer can be used to measure any change in position of the second container when the second container rises or sinks due to expansion or contraction of the gas disposed within the cavity.

2. The pressure measurement system of claim 1 , wherein the first liquid and the second liquid are immiscible such that a boundary layer forms between the first liquid and the second liquid.

3. The pressure measurement system of claim 2 , wherein the second container has a first density and the gas has a second density and a first mass, wherein the first density, second density, and first mass are selected such that a first portion of the second container floats above the boundary layer and a second portion of the second container floats below the boundary layer.

4. The pressure measurement system of claim 1 , wherein the first liquid is decamethyltetrasiloxane and the second liquid is polyethylene glycol (PEG).

5. The apparatus of claim 1 , wherein the gas comprises helium.

6. The apparatus of claim 1 , wherein the reflector comprises one of a mirror or a retro-reflector.

7. A method of measuring pressure comprising:
providing a first container;
pouring a first liquid and a second liquid into the first container, where the first and second liquids are immiscible and the first liquid floats above the second liquid;
providing a second container formed with a cavity and an aperture extending from the cavity to an exterior top side of the second container;
filling the cavity with the first liquid;
inserting a predetermined amount of a gas in the cavity;
submerging the first container within the first and second liquids wherein the aperture at the exterior top side of the second container is in contact with the first liquid;
placing the first container in a space having an unknown pressure; and
recording a displacement of the second container to determine the pressure of the space.

8. The method of claim 7 , wherein recording the displacement of the second container further comprises providing a reflective section on an outer surface of the second container, and directing laser light at the reflective section from a laser interferometer to measure the displacement of the second container.

9. A method of measuring pressure comprising:
providing a pressure measurement system comprising:
a first container;
a first liquid disposed within the first container;
a second liquid disposed within the first container; and
a second container formed with a cavity and an aperture, wherein the second container is disposed within the first container;
wherein the cavity opens to an exterior of the second container through the aperture;
wherein a gas is disposed within the cavity such that the gas is trapped within the second container by pressure;

drawing down pressure in the first container to a vapor pressure of the first liquid for calibration;
placing the first container in a space having an unknown pressure; and
recording a displacement of the second container to determine the pressure of the space.

10. The method of claim 9 , wherein recording the displacement of the second container further comprises providing a reflective section on an outer surface of the second container, and directing laser light at the reflective section from a laser interferometer to measure the displacement of the second container.

Assignees

• Us Navy

Inventors

• Wiest Aaron
• Macdougall Craig Andrew

Classifications

• G01L11/006 Primary

  hydraulic or pneumatic counterbalancing forces · CPC title

• G01L7/22 Primary

  involving floats, e.g. floating bells · CPC title

• G01B11/026

  by measuring distance between sensor and object (G01B11/0608 takes precedence) · CPC title

• G01L7/182

  constructional details, e.g. mounting · CPC title

• G01L7/185

  with mechanical transmitting or indicating means · CPC title