Apparatus for measuring fluid flow

• US 4,372,165 A
• Filed: 09/10/1980
• Issued: 02/08/1983
• Est. Priority Date: 09/11/1979
• Status: Expired due to Term

• Current Assignee: ITT Industries (ITT, Inc.)
• Original Assignee: ITT Industries (ITT, Inc.)
• Inventors: Williamson, Roger J., Pitt, Gillies D.
• Primary Examiner(s): Arnold, Bruce Y.
• Application Number:
  US06/185,629
• Time in Patent Office: 881 Days
• Field of Search: 356/132, 356/133, 356/135, 356/136, 73/861.22, 250/573, 250/574
• US Class Current: 73/861.22
• CPC Class Codes: G01F 1/325 Means for detecting quantities used as proxy variables for swirl

Abstract

A fluid flowmeter of the vortex shedding type. The vortex frequency is determined from variations in the internal reflectivity of a prism 16 mounted in the fluid and coupled to a light source 13 and to a detector/frequency meter 14 via an optical waveguide arrangement 15. Passage of a vortex adjacent the prism 16 causes a temporary change in the local fluid refractive index and hence a change in the intensity of light internally reflected by the prism.

Claims

1. A fluid flowmeter of the type in which the flow velocity of a fluid is determined by measuring the frequency at which vortices are shed from a bluff body arranged in the fluid stream, comprising:

a prism mounted on said bluff body in the fluid stream;

a light source and means for directing light into said prism so as to provide an internally reflected beam;

means for measuring the intensity of said reflected beam; and

a frequency meter coupled to the output of said intensity measuring means to determine the rate of variation of said reflected beam intensity, said prism being constructed with respect to said light directing means so that the reflectivity of at least one surface of said prism varies in response to variations in the refractive index of the fluid caused by passing fluid vortices.

2. A flowmeter according to claim 1 in which said light source is defined as a monochromatic source.

3. A fluid flowmeter as claimed in claim 2, and wherein said prism is so constructed that light strikes at least one facet substantially at the critical angle.

4. A fluid flowmeter as claimed in claim 2 or 3, and wherein said light source is a semiconductor light-emitting device.