Method and apparatus for quantitative particle determination in fluids

• US 6,315,955 B1
• Filed: 01/16/1998
• Issued: 11/13/2001
• Est. Priority Date: 04/06/1995
• Status: Expired due to Term

• Current Assignee: Delaval International AB (Tetra Laval Holdings BV)
• Original Assignee: Delaval International AB (Tetra Laval Holdings BV)
• Inventors: Klein, Cornelis
• Primary Examiner(s): WALLENHORST, MAUREEN
• Application Number:
  US08/930,144
• Time in Patent Office: 1,397 Days
• Field of Search: 422/68.1, 422/73, 422/82.05, 422/82.09, 436/10, 436/63, 436/164, 356/300, 356/311, 356/317, 356/337, 356/338, 356/340, 356/342, 356/343, 356/432, 356/433, 356/435, 356/436, 356/441, 356/442, 356/445, 356/448
• US Class Current: 422/73
• CPC Class Codes: G01N 15/01 specially adapted for biological cells, e.g. blood cells investigating sedimentation of particle suspensions in blood G01N15/05
• CPC Class Codes: G01N 15/0211 Investigating a scatter or diffraction pattern
• CPC Class Codes: G01N 15/06 Investigating concentration of particle suspensions by weighing G01N5/00; investigating sedimentation of particle suspensions G01N15/04; investigating individual particles G01N15/10
• CPC Class Codes: G01N 15/075 by optical means
• CPC Class Codes: G01N 2015/003 in liquids, e.g. emulsion
• CPC Class Codes: G01N 2015/0053 in liquids, e.g. trouble
• CPC Class Codes: G01N 2015/0687 in solutions, e.g. non volatile residue
• CPC Class Codes: G01N 33/04 Dairy products

Abstract

The present invention includes a method and an apparatus for the quantitative determination of particles in fluid. The apparatus of the invention includes an emitters set of one or more light emitters, in combination with a detector set of one or more light detectors sensitive to the output of the emitters. During analysis of the sample, data from a plurality of signal paths between the emitter and detector sets are gathered. This information is subsequently evaluated by comparison with known data for different fluid particle contents. Some differentiation between different particles in a fluid sample are possible in many embodiments. Typical uses include analysis of milk and dairy fluids, blood samples, lubricants, suspensions of pigments, etc.

Claims

1. Apparatus for quantitative particle determination in fluids having a particle content, said apparatus comprising:

an emitter set comprising one or more light emitters, each acting as a point light source, providing one or more sample light signals as output;

a detector set comprising one or more light detectors sensitive to the output of the light emitters, wherein the sample light signals from a plurality of discrete sample light signal paths between the emitter and detector sets are received by the detector set during analysis of a sample, the detector set being operable to discern between different sample light signal paths;

a signal connection adapted for communicating information received from the detector set to a processor for processing one or more values indicative of the presence of particles within a sample fluid; and

a feedback detector positioned to receive incident light from an emitter of said emitter set;

said feedback detector providing an output used to compensate for any drifting of the emitter'"'"'s output from a predetermined ideal norm through either or both of;

i) control of the emitter'"'"'s output, and

ii) influencing the sensitivity of at least one light detector to match the light output of said emitter;

the detector set providing, for a plurality of different sample light signal paths, individual output values which can be evaluated by a processor for providing a value indicative of the fluid particle content of the fluid sample being analyzed.

2. Apparatus as claimed in claim 1 in which the detector set is arranged to detect at least one set of scattered or reflected light signals due to reflectance by particles present within the fluid.

3. Apparatus as claimed in claim 1 in which said feedback detector influences:

either or both the voltage and current of at least one light emitter whose directly incident light it detects to maintain the emitter light output at a predetermined level.

4. Apparatus as claimed in claim 3, in which said feedback detector comprises a light emitter of substantially the same type and characteristics as the light emitter whose output it monitors.

5. Apparatus as claimed in claim 1 in which said sample light signal paths differ from each other by at least one of:

a path length through the fluid sample being analyzed, and

a relative path angle through the fluid sample being analyzed.

6. Apparatus as claimed in claim 1 in which one or more sample light signals are within the infrared region of the electromagnetic spectrum.

7. Apparatus as claimed in claim 6 in which one or more sample light signals have a wavelength in the regions 750-1200 nm or 3000-10000 nm.

8. Apparatus as claimed in claim 1 in which a light emitter comprises a light emitting diode (LED).

9. Apparatus as claimed in claim 1 in which a light detector comprises a photo diode, light emitting diode (LED), photo transistor, or other opto-electronic device.

10. Apparatus as claimed in claim 1 wherein said emitter set comprises a plurality of light emitters at different positions along a wall or walls of a sample cell, or positioned to be present along a wall or walls of an inserted sample cell.

11. Apparatus as claimed in claim 10 in which said emitters are arranged in a substantially radial manner about a substantially curved sample cell, or cell holder.

12. Apparatus as claimed in claim 10, in which there is provided a plurality of groups of emitter set and detector set pairs, each group of emitter and detector sets functioning substantially independently of other groups and the output of each detector set being considered by a processor when providing a value indicative of particle presence within the fluid sample being analyzed.

13. Apparatus as claimed in claim 1 in which the output of at least one light emitter is pulsed during analysis of a sample fluid.

14. Apparatus as claimed in claim 13 comprising aplurality of pulsed light emitters, and in which the detector set, or an individual detector of the detector set, detects substantially the output of a single light emitter, or combination thereof, at a time during analysis of a sample fluid;

the pulsing of said light emitters being synchronised to allow the detection of the output of individual light emitters, or groups thereof.

15. Apparatus as claimed in claim 1 in which the output of at least one light emitter is varied in its output intensity during analysis of a sample fluid.

16. Apparatus as claimed in claim 15 in which the detector set, or an individual detector of the detector set, produces a signal available for evaluation by a processor at more than one output intensity of said light emitter(s).

17. Apparatus as claimed in claim 1 in which at least one detector of the detector set is positioned and operated to receive at least one signal during analysis of a sample fluid which comprises purely reflected or scattered light, and not directly transmitted light, from one or more emitters of the emitter set.

18. Apparatus as claimed in claim 1 in which the output of the detector set is converted to a digital format.

19. Apparatus as claimed in claim 18 in which data is prepared into packets which is available to a processer for evaluation in producing a value indicative of particle presence within a sample fluid.

20. Apparatus as claimed in claim 1 which includes a processer for producing one or more values indicative of the presence of particles within a sample fluid.

21. Apparatus as claimed within claim 20 in which said processor compares values produced by the detector set with stored calibration reference values, the comparison producing values indicative of the presence of one or more different types of particles within a sample fluid.

22. Apparatus as claimed in claim 21 in which the stored values comprise calibration data relating to chosen standards.

23. Apparatus as claimed in claim 22 in which the comparison of data is based on either or both linear regression or Fourier transformations.

24. Apparatus as claimed in claim 1 which includes, or is configured to include, a sample cell capable of allowing a continuous flow of sample therethrough.

25. Apparatus as claimed in claim 1 which is connected to a milk line.

26. Apparatus as claimed in claim 1 which is connected to an oil line.

27. Apparatus as claimed in claim 1 which is connected to a lubricant line.

28. Apparatus as claimed in claim 1, wherein said feedback detector also provides an output whose value can be evaluated by a processor when providing a value indicative of the fluid particle content.

29. A method of quantitative determination of the levels of one or more different particles in a fluid comprising:

i) transmitting one or more light signals as output from one or more emitters into a fluid sample wherein the emitters act as point light sources;

ii) detecting the light signals from a plurality of different discrete sample light signal paths as output with one or more detectors, wherein different discrete sample light signal paths are discemable one from the other; and

ii) making the detected output for each discrete sample light signal path available for subsequent evaluation by a processor;

wherein an output value is obtained from a feedback detector positioned to receive incident light from at least one emitter, the output value being used as a correction for drift in the output of said emitter by either or both of i) control of the emitter'"'"'s output, and ii) influencing the sensitivity of at least one light detector to match the light output of said emitter.

30. A method as claimed in claim 29 in which the detected light signals differ by at least one of the following:

a path length through the fluid sample being analyzed;

a relative path angle through the fluid sample being analyzed;

the output intensity of the emitter producing said signal;

the proportion of transmitted to reflected or scattered light, and

wavelength.

31. A method as claimed in claim 29 in which the detected output is compared by either or both of linear regression, and Fourier transform analysis, with stored calibration reference values to produce values indicative of the quantitative levels of one or more different types of particles within said fluid.

32. A method as claimed in claim 31 in which the operation of different emitter(s) and detector(s) are co-ordinated to allow the collection of light signals from different combinations thereof.

33. A method as claimed in claim 29 in which the light signals are pulsed.

34. A method as claimed in claim 29 wherein at least one light signal comprises light within the infrared portion of the electromagnetic spectrum.

35. A method as claimed in claim 29 for the determination of particle levels in at least one of:

milk and other dairy based fluids;

substances containing fluidised fat particles, globules, and suspensions;

blood, plasma, semen, urine and other biological fluids;

oils and lubricants, and

inks, paints, and liquid pigments.

36. A method as claimed in claim 35 when applied to milk and other dairy based fluids, the method being used to indicate the levels of at least one of:

fat, protein, lactose, and somatic cell count.

37. A method of determining the flow rate of a fluid flowing in a conduit from a first position to a second position at a defined distance downstream therefrom, comprising:

(i) performing the method of claim 29 to provide a quantitative determination of the level of one or more particles at the said first position at a start time;

(ii) at said second position, repeating the method of claim 29 and recording a stop time when the said quantitative determination of the level of one or more particles of step (i) is obtained; and

(iii) calculating an elapsed time between the said start and stop times and using said elapsed time and said defined distance between the first and second positions to determine the flow rate.

38. Apparatus for particle determination in fluids, said apparatus including:

an emitter set comprising a plurality of light emitters, each received in a conduit providing an optical path convergent at a common focus point, each acting as a point light source, providing one or more light signals as output;

a detector set comprising one or more light detectors sensitive to the output of the light emitters, wherein said common focus point is substantially on a said one of said light detectors, and wherein the sample light signals from a plurality of discrete sample light signal paths between the emitter and the detector sets are received by the detector set during analysis of a sample, the detector set being operable to discern between different sample light signal paths;

the apparatus including compensation for any drifting of an emitter'"'"'s output from a predetermined ideal norm;

the detector set providing, for a plurality of different sample light signal paths, individual output values which can be evaluated by a processor for providing a value indicative of the fluid particle count.