Fluorometric sensor

A fluorometric sensor, comprising:

• an immersible sensor head, comprising:
• a plastic housing comprising a cutout in a lateral surface of the housing, the cutout defining a first wall with a planar first exterior surface and a second wall with a planar second exterior surface, the first and the second exterior surfaces intersecting at a first angle;
• a light source chamber comprising an ultraviolet (UV) light source that emits a first UV wavelength for excitation of a water sample within an analytical area proximate the sensor head;
• a light source window positioned in the first wall that transmits the first UV wavelength from the light source chamber into the analytical area, the light source window comprising a first channel extending through the first wall orthogonal to the first exterior surface and a first ball lens positioned in the first channel, the first ball lens having a radius R1 and the first channel having a nominal diameter less than 2R1 such that the first channel is deformed about the first ball lens, securing the first ball lens within the first channel and creating a continuous impermeable seal about the first ball lens between the light source chamber and the analytical area;
• a detector chamber comprising a UV detector that detects fluorescent emissions at a second UV wavelength from the analytical area;
• and
• a detector window positioned in the second wall that transmits the second UV wavelength from the analytical area into the detector chamber, the detector window comprising a second channel extending through the second wall orthogonal to the second exterior surface and a second ball lens positioned in the second channel, the second ball lens having a radius R2 and the second channel having a nominal diameter less than 2R2 such that the second channel is deformed about the second ball lens, securing the second ball lens within the second channel and creating a continuous impermeable seal about the second ball lens between the detector chamber and the analytical area;
• and
• a controller coupled to the UV detector and adapted to calculate a concentration of a chemical in the water sample within the analytical area based on the detected fluorescent emissions;
• wherein
• the first angle is from about 60 degrees to about 120 degrees,
• an axis of the first channel and an axis of the second channel cross at an intersect point in the analytical area,
• a first distance from the intersect point to the first exterior surface is from about R1 to about 3R1,
• a second distance from the intersect point to the second exterior surface is from about R2 to about 3R2,
• a third distance from a center of the first ball lens to the intersect point is from about 1.2R1 to about 3.2R1, and
• a fourth distance from a center of the second ball lens to the intersect point is from about 1.2R2 to about 3.2R2.

A method for making an immersible fluorometric sensor head, comprising:

• providing a plastic workpiece;
• forming a light source chamber in the workpiece;
• forming a detector chamber in the workpiece;
• forming a cutout in a lateral surface of the workpiece, the cutout and the light source chamber defining a first wall with a first exterior planar surface, the cutout and the detector chamber defining a second wall with a second exterior planar surface, the first and the second exterior planar surfaces intersecting at a first angle;
• forming a light source window in the first wall, comprising forming a first channel extending through the first wall and positioning a first ball lens in the first channel, the first ball lens having a radius R1 and the first channel having a nominal diameter less than 2R1, the positioning comprising pushing the first ball lens into the first channel from the light source chamber and deforming the first channel about the first ball lens to secure the first ball lens and create a continuous impermeable seal about the first ball lens between the light source chamber and an exterior of the sensor head;
• forming a detector window in the second wall, comprising forming a second channel extending through the second wall and positioning a second ball lens in the second channel, the second ball lens having a radius R2 and the second channel having a nominal diameter less than 2R2, the positioning comprising pushing the second ball lens into the second channel from the detector chamber and deforming the second channel about the second ball lens to secure the second ball lens and create a continuous impermeable seal about the second ball lens between the detector chamber and the exterior of the sensor head;
• positioning an ultraviolet (UV) light source in the light source chamber that emits a first UV wavelength through the light source window for excitation of a water sample within an analytical area proximate the sensor head;
• and
• positioning a UV detector in the detector chamber that detects fluorescent emissions at a second UV wavelength through the detector window from the analytical area.