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Title: Method and apparatus for monitoring and measuring the surface tension of a fluid using fiber optics

A non-contact method and apparatus are described for measuring and monitoring the surface of a fluid using fiber optics and interferometric detection to permit measurement of mechanical characteristics of fluid surfaces. The apparatus employs an alternating electric field gradient for generating a capillary wave on the surface of the fluid. A fiber optic coupler and optical fiber directs a portion of a laser beam onto the surface of the fluid, another portion of the laser beam onto the photo sensor, and directs light reflected from the surface of the fluid onto the photo sensor. The output of the photo sensor is processed and coupled to a phase sensitive detector to permit measurement of phase shift between the drive signal creating the capillary wave and the detected signal. This phase shift information is then used to determine mechanical properties of the fluid surface such as surface tension, surface elasticity, and surface inhomogeneity. The resulting test structure is easily made compact, portable, and easy to align and use. 4 figures.
Inventors:
; ; ;
Issue Date:
OSTI Identifier:
5051446
Assignee:
Northwestern Univ., Evanston, IL (United States) PTO; EDB-94-077046
Patent Number(s):
US 5303030; A
Application Number:
PPN: US 7-801153
Contract Number:
FG02-84ER45125
Resource Relation:
Patent File Date: 2 Dec 1991
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; FLUIDS; SURFACE TENSION; TENSIOMETERS; DESIGN; OPERATION; PORTABLE EQUIPMENT; EQUIPMENT; MEASURING INSTRUMENTS; SURFACE PROPERTIES; 440800* - Miscellaneous Instrumentation- (1990-)