Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Reexamination Certificate
1999-07-27
2001-12-04
Moller, Richard A. (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
C356S928000
Reexamination Certificate
active
06324900
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and to a device for optically measuring the transparency of a liquid.
The technical field of the invention is the field of research or of analyzing materials, in particular liquids, by optical means.
The main application of the invention is to be able to determine the turbidity of water, essentially for monitoring its quality, and in particular by detecting matter in suspension or in an emulsion, such as hydrocarbons, which might be mixed therewith; the way in which this turbidity is determined is described in European and French standard NF, EN 2707 of 1994, which reproduces in full international standard ISO 7027 of 1990 and to which the person skilled in the art can refer for a better understanding of the present invention if that should be necessary.
BACKGROUND OF THE INVENTION
It is recalled in particular that in liquids, turbidity is the result of non-dissolved matter that is finely dispersed: it can be determined by measuring the decrease in the intensity of light flux as it passes through the liquid in which part of the light is absorbed, or by measuring the intensity of the light that is diffused, and in particular at 90°; light diffusion is a property of liquids which can be used for measuring such turbidity; the above-referenced European standard describes four optical methods for determining water turbidity to obtain information on site about surface water, potable water, and residual water. Since turbidity is an overall parameter for determining the level of pollution or the effectiveness of an industrial method, the present invention can have numerous applications, such as:
monitoring waste at the outlet from sewage stations, in terms of cloudy residual water;
monitoring sewage methods or industrial methods;
determining the quality of water in settling tanks, in river water, and in lake water;
detecting operating anomalies with filters, industrial separators;
monitoring industrial effluents, and in particular oil effluents;
monitoring deballasting by oil tankers; and
monitoring discharges of bilge water into the sea by ships.
Numerous equipments have thus been developed to enable the turbidity in an aqueous medium to be measured, and more recently to comply with the above standard; some such apparatuses have constituted the subject matter of patent applications, such as application EP 596231 published on May 11, 1994 and international application WO 9800701 published on Jan. 8, 1998, which describe the combination of a nephelometer and a turbidimeter; it is recalled that nephelometry relates to measuring the concentration of an emulsion on the basis of its transparency.
Although those optical measurement apparatuses give full satisfaction concerning optically measuring the intensity of a given light after it has traveled a determined distance through the liquid under inspection, measurement proper is often spoilt by the fact that dirt such as oil can become deposited on the surfaces of the optical interfaces immersed in the liquid; the interfaces serve firstly to emit light into the liquid and secondly to receive light therefrom for measurement purposes: at present, methods and devices based on windshield-wiper principles are unsatisfactory and require assiduous maintenance.
OBJECTS AND SUMMARY OF THE INVENTION
The problem posed is thus to be able to guarantee that said optical interface surfaces are clean prior to taking each measurement so that the measurements are reliable, and to do so without using a mechanical device that requires intensive maintenance.
A solution to the problem posed is a method of optically measuring the transparency of a liquid by means of a turbidity analyzer comprising at least one emitter of light that passes through an optical interface piece such as a bar, an optical fiber, etc., providing an interface with the liquid that is illuminated in this way, and at least one measurement cell receiving a portion of said light via a second optical interface piece, which portion of light has traveled over a given distance through said liquid. According to the invention:
ultrasound waves are generated in all directions around the emitting and receiving optical/liquid interfaces of said optical pieces in contact with said liquid, thereby cleaning said interface surfaces or preventing them from becoming dirtied, in particular when gaseous microcavities created in this way in the liquid implode; and
the emission of said ultrasound waves is stopped and a measurement is taken of the light received by the cell.
In a preferred embodiment, the device of the invention has a probe that can be immersed in the liquid, the probe having a liquid-proof housing that contains at least the light emitter, the measurement target, the associated optical interface pieces, and the ultrasound generator whose outlet has said two optical pieces integrated therein, thereby ensuring that they have an emission surface that is common therewith.
The result is novel methods and devices for measuring the transparency of a liquid and satisfying the problem posed, in particular by enabling the turbidity of said liquid to be measured with the desired degree of reliability. Unlike present turbidimeters, the device of the invention makes it possible in particular to perform high quality measurements on-site, regardless of the degree to which the liquid being analyzed is dirty: the emitted ultrasound prevents any development of microorganisms and also prevents any dirt being deposited on the optical interfaces.
In addition, the microcavitation caused by the ultrasound waves serves to homogenize the liquid medium by emulsifying it, in particular when it is confined in a measurement cell: this phenomenon makes it possible to make more reliable and to simplify detection of substances such as residual hydrocarbons in oil waste; otherwise these hydrocarbons tend to amalgamate in some portions of the liquid, thereby giving rise to false measurements since if such an amalgamation lies in the light beam, then the turbidity measurement taken will be much higher than the average turbidity of the medium, and conversely if an amalgamation is not in the beam, then the measurement will be much too small, and in both cases the measurement will not be representative of the mean turbidity of the liquid.
In addition, installation conditions are quite simple and adaptable to numerous sites, either merely by immersing a probe in the liquid, or by inserting optical and ultrasound interfaces in the wall of pipework or in a miniature emulsifying vessel, etc. . . . .
Other advantages of the present invention could also be mentioned, but those mentioned above suffice to demonstrate the novelty and the advantage of the invention.
REFERENCES:
patent: 5377005 (1994-12-01), Meyer
patent: 6134952 (2000-10-01), Garver et al.
patent: 9015235 (1991-02-01), None
patent: 0596231 (1994-05-01), None
patent: 0634228 (1995-01-01), None
patent: 1604691 (1981-12-01), None
patent: 2052684 (1977-04-01), None
patent: 1320449 (1989-12-01), None
patent: 9800701 (1998-01-01), None
Patent Abstracts of Japan vol. 14, No. 128 (P-1019), Mar. 9, 1990 & JP 01 320449 A (NEC CORP), Dec. 26, 1989.
Patent Abstracts of Japan vo. 001, No. 121 (E-053(, Oct. 13, 1977 & JP 52 052684 A (Chiyouonpa Kogyo KK), Apr. 27, 1977.
Bruno Georges V.
Minard Alain P.
Ladas & Parry
Moller Richard A.
Societe d'Etude et de Realisation d' Equipments Specia
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