Super-Accurate Liquid-Level Sensing for Industrial Applications

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This technology provides an unprecedented level of accuracy in measuring liquid levels, overcoming the many limitations associated with currently available methods. This capability is crucial in various industries that require liquid level measurement within large containers or for materials that are difficult to measure (e.g., cryogenic liquids).

How It Works:
Developed at NASA’s Armstrong Flight Research Center, this extraordinarily accurate method for measuring liquid levels uses fiber Bragg grating (FBG) sensors located along a single fiber optic cable. These sensors actively discern between the liquid and gas states along the continuous fiber, accurately pinpointing the liquid level to within a quarter inch.

The technology uses a resistive heater wire bundled with the optical fiber. The heater is pulsed to induce a local temperature change along the fiber. The fiber Bragg grating data are used to monitor the subsequent cooling of the fiber. The section of fiber in the liquid cools more rapidly than the portion of the fiber in the gas above the liquid. The measurement system accurately establishes the precise location of this liquid-to-gas transition.

What Makes It Better:
NASA’s technology represents a significant advancement in the state of the art for measuring cryogenic liquid levels. Conventional methods for measuring cryogenic liquid levels rely on diodes strategically placed along a rod or rack. These cryogenic diodes are mounted in preselected, relatively widely spaced positions along the length of the rod/rack, providing limited and imprecise data. Furthermore, each diode has two wires associated with it, which means a single system may require a large number of wires, making installation, connectivity, and instrumentation cumbersome.

NASA’s innovation offers several advantages:
-- Precise: Provides liquid measurements at 0.25-inch intervals
-- Simple: Requires just two wires and a fiber optic strand for the entire system, greatly simplifying installation and instrumentation
-- Robust: Is not susceptible to electromagnetic interference (EMI) and can withstand corrosive or toxic liquids

Potential Uses/Markets:
Dubbed CryoFOSS because it was originally designed to monitor cryogenic fuel levels in rockets using fiber optic sensing system (FOSS) technology, this innovation can be used in a wide range of applications beyond cryogenic liquids. For example:
-- Aerospace, especially liquid-fuel launch vehicles and satellites
-- Chemical or refinery plants to monitor the facility’s fluid flow
-- Industrial tanks to measure level of cryogenic or other liquids (e.g., for liquid natural gas storage and transport)
-- Oil and gas storage monitoring for the energy industry
-- Food and beverage manufacturing
-- Pharmaceutical manufacturing
-- Medical and hospital operations

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  • Name:
    Allen Parker
  • Type of entry:
    Team members:
    Allen Parker, NASA’s Armstrong Flight Research Center
    Lance Richards, NASA’s Armstrong Flight Research Center
    Anthony Piazza, NASA’s Armstrong Flight Research Center
    Hon (Patrick) Chan, NASA’s Armstrong Flight Research Center
    John Bakalyar, NASA’s Armstrong Flight Research Center
  • Profession:
  • Allen is inspired by:
    I love to share the fiber optic sensing technology I have been working on with other researchers and engineers from different backgrounds. I get really excited when they are able to apply the technology in ways we haven’t dreamt of.
  • Patent status: