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Title: Optical pressure/density measuring means

An apparatus and method for rapidly and accurately determining the pressure of a fluid medium in either a static or dynamic state. The pressure is determined by making a measurement of the velocity of a light beam that is directed through the fluid medium along a pathway that enables an integrated pressure measurement to be made along the pathway, rather than making such a measurement only at a single point in the medium. A HeNe laser is configured to emit a beam of two frequencies separated by about 2 MHz. One of these beam frequencies is directed through the fluid medium and is reflected back through the medium to a non-linear diode detector. The other beam frequency is passed directly to a diode detector without traversing said medium. The diode detector is operated to determine the frequency shift or beat frequency between the two beam frequencies. Any variation in the frequency of said reflected beam that is caused by a change in its velocity as it is passed through the fluid medium causes a change in the beat frequency. This beat frequency change is then converted to an output signal value corresponding to the pressure of the medium. The measurementmore » instrument apparatus is remotely positioned relative to the medium being measured, thus the apparatus is immune from electro-magnetic interference and can operate in conditions of high radiation, corrosion and extraordinarily high temperature.« less
Inventors:
 [1]
  1. (Manorville, NY)
Issue Date:
OSTI Identifier:
869880
Assignee:
Associated Universities, Inc. (Washington, DC) BNL
Patent Number(s):
US 5414509
Application Number:
08/027,878
Contract Number:
AC02-76CH00016
Research Org:
ASSOC UNIVERSITIES INC
Country of Publication:
United States
Language:
English
Subject:
optical; pressure; density; measuring; means; apparatus; method; rapidly; accurately; determining; fluid; medium; static; dynamic; determined; measurement; velocity; light; beam; directed; pathway; enables; integrated; single; hene; laser; configured; emit; frequencies; separated; mhz; reflected; non-linear; diode; detector; frequency; passed; directly; traversing; operated; determine; shift; beat; variation; caused; change; causes; converted; output; signal; value; corresponding; instrument; remotely; positioned; relative; measured; immune; electro-magnetic; interference; operate; conditions; radiation; corrosion; extraordinarily; temperature; pressure measurement; frequency shift; light beam; output signal; fluid medium; beat frequency; positioned relative; reflected beam; beam frequency; accurately determining; passed directly; measuring means; measurement instrument; value corresponding; diode detector; frequency change; signal value; linear diode; /356/

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