Compact sensor for measuring turbidity or fluorescence in a fluid sample

1. A method of making a turbidity sensor, the method comprising the steps of:

enclosing a plurality of optical components within a wedge-shaped sensor housing having: an outer surface shape that is a portion of a circle, a first and a second surface extending from a vertex region and connecting to ends of said outer surface shape, with a unique maximum straight line distance between said outer surface ends, and a distal sensing end volume in which said optical components are confined that is less than or equal to 20 cm 3 ;

wherein said plurality of optical components comprise an optical source, a beam splitter, a reference photodetector, and a signal photodetector that are aligned with said unique maximum straight line;

providing an emission window through a distal sensing surface of said wedge-shaped sensor housing for passing electromagnetic radiation from said optical source to a sample chamber; and

providing a collection window through a distal sensing surface of said sensor housing for collecting scattered electromagnetic radiation from said sample chamber to said signal photodetector;

thereby providing a turbidity sensor.

2. The method of claim 1 , wherein the distal sensing end volume is greater than 1 cm 3 .

3. The method of claim 1 , wherein the turbidity sensor comprises:

said distal sensing end having:

said vertex region;

said first surface extending from said vertex region and ending at a first surface end point;

said second surface extending from said vertex region and ending at a second surface end point, wherein said first surface and said second surface extend in different directions to form a vertex angle at said vertex region;

said outer surface shape is a convex-curved outer surface that extends between said first surface end point and said second surface end point;

said distal sensing surface defined by edges of said first surface, said second surface, said vertex region, and said curved outer surface; wherein a separation distance between said first surface end point and said second surface end point defines said unique maximum straight line distance on said distal sensing surface;

said distal sensing end volume having a cross-section formed by said vertex region, said first surface, said second surface and said curved outer surface;

an optical system positioned in said distal sensing end volume comprising:

the optical source to generate a beam of electromagnetic radiation;

the emission window through said distal sensing surface, wherein the emission window is in optical communication with said beam of electromagnetic radiation and configured to pass at least a portion of said beam of electromagnetic radiation from said distal sensing end volume through said distal sensing surface to a sample volume adjacent to said distal sensing surface;

the collection window through said distal sensing surface, wherein the collection window is configured to pass at least a portion of an incoming beam of scattered electromagnetic radiation from particles suspended in fluid in the sample chamber in a collection direction to said distal sensing end volume; and

wherein said signal photodetector is configured to detect said beam of incoming electromagnetic radiation in said collection direction;

wherein said plurality of optical components are positioned in an optical plane that extends substantially perpendicular to said distal sensing surface and that is substantially aligned with a notional line corresponding to said maximum unique straight line distance.

4. The method of claim 3 , wherein said optical system further comprises:

said beam splitter positioned in optical communication with said optical source; and

said reference photodetector detects electromagnetic radiation reflected by said beam splitter.

5. The method of claim 3 , wherein said vertex angle is greater than or equal to 30° and less than or equal to 90°.

6. The method of claim 1 , wherein said outer surface shape has a radius of curvature that is less than or equal to 3 cm.

7. The method of claim 1 , wherein said optical system is positioned within 5 cm from said distal sensing surface.

8. The method of claim 1 , wherein said optical source and said signal photodetector are configured to provide a sensing height from said distal sensing surface of between 1 mm and 3.6 mm and a sensing volume of between 10 mm 3 and 30 mm 3 .

9. The method of claim 8 , wherein said optical source and said photodetector are configured to provide a nominal optical path length between said optical source and said signal photodetector in water that is between 4 mm and 10 mm.

10. The method of claim 1 , wherein said first surface and said second surface are flat-faced and said sensor is configured for insertion into a multiparameter sonde comprising a plurality of independent sensors, wherein the sensors in combination provide a substantially circular cross-sectional footprint.

11. A method of measuring turbidity in a fluid sample by:

providing a turbidity sensor, wherein said turbidity sensor comprises:

a distal sensing end having:

a vertex region;

a first surface extending from said vertex region and ending at a first surface end point;

a second surface extending from said vertex region and ending at a second surface end point, wherein said first surface and said second surface extend in different directions to form a vertex angle at said vertex region;

a convex-curved outer surface that extends between said first surface end point and said second surface end point;

a distal sensing surface defined by edges of said first surface, said second surface, said vertex region, and said curved outer surface; wherein a separation distance between said first surface end point and said second surface end point defines a maximum straight line distance on said distal sensing surface;

a distal sensing end volume having a cross-section formed by said vertex region, said first surface, said second surface and said curved outer surface;

an optical system positioned in said distal sensing end volume comprising:

an optical source to generate a beam of electromagnetic radiation;

an emission window through said distal sensing surface in optical communication with said beam of electromagnetic radiation and configured to pass at least a portion of said beam of electromagnetic radiation from said distal sensing end volume through said distal sensing surface to a sample volume adjacent to said distal sensing surface;

a collection window through said distal sensing surface configured to pass at least a portion of an incoming beam of scattered electromagnetic radiation from particles suspended in fluid in the sample chamber in a collection direction to said distal sensing end volume; and

a signal photodetector configured to detect said beam of incoming electromagnetic radiation in said collection direction;

wherein said optical system is positioned in an optical plane that extends substantially perpendicular to said distal sensing surface and that is substantially aligned with a notional line corresponding to said maximum straight line distance;

introducing a fluid sample to said distal sensing end;

introducing electromagnetic radiation to said fluid sample from said optical source;

detecting a reference light intensity with said reference photodetector;

detecting a signal light intensity with said signal photodetector; and

calculating a ratio of said reference and signal light intensity;

thereby measuring turbidity in said fluid sample.

12. The method of claim 11 , wherein said distal sensing surface has a surface area that is between 3.2 cm 2 and 3.9 cm 2 , and said maximum straight line distance is greater than or equal to 2.5 cm and less than or equal to 3.1 cm.

13. The method of claim 11 , wherein said optical system further comprises:

a beam splitter positioned in optical communication with said optical source; and

a reference photodetector to detect electromagnetic radiation reflected by said beam splitter.

14. The method of claim 13 , wherein said vertex angle is greater than or equal to 30° and less than or equal to 90°.

15. The method of claim 11 , wherein said outer surface shape has a radius of curvature that is less than or equal to 3 cm.

16. The method of claim 11 , wherein said optical system is positioned within 5 cm from said distal sensing surface.

17. The method of claim 11 , wherein said optical source and said signal photodetector are configured to provide a sensing height from said distal sensing surface of between 1 mm and 3.6 mm and a sensing volume of between 10 mm 3 and 30 mm 3 .

18. The method of claim 17 , wherein said optical source and said photodetector are configured to provide a nominal optical path length between said optical source and said signal photodetector in water that is between 4 mm and 10 mm.

19. The method of claim 11 , wherein said first surface and said second surface are flat-faced and said sensor is configured for insertion into a multiparameter sonde comprising a plurality of independent sensors, wherein the sensors in combination provide a substantially circular cross-sectional footprint.

20. A method of making a fluorescence-measuring sensor, the method comprising the steps of:

enclosing a plurality of optical components within a wedge-shaped sensor housing having an outer surface shape that is a portion of a circle a first and second surface extending from a vertex region and connecting to ends of said outer surface shape, with a unique maximum straight line distance between said outer surface ends, and a distal sensing end volume in which said optical components are confined that is less than or equal to 20 cm 3 ;

wherein said plurality of optical components comprise an optical source, a beam splitter, a reference photodetector, and a signal photodetector that are aligned with said unique maximum straight line;

providing an optical window through a distal sensing surface of said wedge-shaped sensor housing for passing a beam of electromagnetic radiation from said optical source to a sample chamber, wherein the optical window is configured to:

pass at least a portion of said beam of electromagnetic radiation from said distal sensing end volume through said distal sensing surface to a fluid sample volume adjacent to said distal sensing surface, wherein at least a portion of said excitation band of wavelengths is provided to said fluid sample volume;

pass at least a portion of emitted fluorescent electromagnetic radiation from fluorescent molecules suspended in said fluid sample through said distal sensing end volume;

providing an emission filter in optical communication with said emitted fluorescent electromagnetic radiation to pass light of a desired band of wavelengths to said signal photodetector configured to detect said light of the desired band of wavelengths;

thereby providing a fluorescence-measuring sensor.