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Provided is a cleanable conductivity sensor and related methods having a distal sensing end in which active sensing elements are positioned and an outer fin specially configured to minimize unwanted interference without impacting the ability for automated cleaning of the distal sensing end. A rotata

Provided is a cleanable conductivity sensor and related methods having a distal sensing end in which active sensing elements are positioned and an outer fin specially configured to minimize unwanted interference without impacting the ability for automated cleaning of the distal sensing end. A rotatable wiper or brush may be periodically rotated over the distal sensing end, thereby removing unwanted biological build-up and avoiding fouling, thereby increasing the sensor deployment time without active intervention and maintenance.

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1. A cleanable conductivity sensor comprising: a substantially planar distal sensing end comprising: a vertex region;a first inner end edge extending from said vertex region to a first inner end point;a second inner end edge extending from said vertex region to a second inner end point, wherein said

1. A cleanable conductivity sensor comprising: a substantially planar distal sensing end comprising: a vertex region;a first inner end edge extending from said vertex region to a first inner end point;a second inner end edge extending from said vertex region to a second inner end point, wherein said first inner end edge and said second inner end edge extend in directions to define a vertex angle;an outer end edge that extends between said first inner end point and said second inner end point;an outer fin extending from said distal sensing end and positioned adjacent to at least a portion of said outer end edge to define a conductivity measurement cell volume; anda plurality of electrodes having a distal end positioned at or proximate to said distal sensing end and between said outer fin and said vertex region to measure conductivity in said conductivity measurement cell volume;wherein said plurality of electrodes distal ends, said vertex region, said first inner end edge, said second inner end edge and said outer end edge form a single plane. 2. The cleanable conductivity sensor of claim 1, further comprising an inner fin extending from said distal sensing end, wherein said outer fin and said inner fin are separated from each other by a fin separation distance to define said conductivity measurement cell volume. 3. The cleanable conductivity sensor of claim 2, wherein said outer fin and said inner fin have a laterally-directed shape that corresponds to a shape of said outer end edge; and said outer end edge has a curved shape, wherein said curved shape is a portion of a circle having a radius of curvature that is greater than or equal to 1 cm and less than or equal to 20 cm and said vertex angle is 45°. 4. The cleanable conductivity sensor of claim 2, having an outer fin surface area and an inner fin surface area, wherein: said outer fin surface area is greater than or equal to 2 cm2 and less than or equal to 8 cm2; andsaid inner fin surface area is greater than or equal to 0.3 cm2 and less than or equal to 2 cm2. 5. The cleanable conductivity sensor of claim 2, wherein said fin separation distance is greater than or equal to 0.5 cm and less than a length of said first or second inner end edge. 6. The cleanable conductivity sensor of claim 1, wherein said outer fin has a fin outer-facing surface positioned within 3 mm of said outer end edge. 7. The cleanable conductivity sensor of claim 6, wherein said fin outer-facing surface extends continuously from at least a portion of said outer end edge to form a continuous outer-facing surface. 8. The cleanable conductivity sensor of claim 1, wherein said first inner end edge and said second inner end edge each extend a radial distance from said vertex region, said radial distance selected from a range that is greater than or equal to 1 cm and less than or equal to 20 cm. 9. The cleanable conductivity of sensor of claim 8, wherein said outer end edge is curved, and said curve is a portion of a circle. 10. The cleanable conductivity sensor of claim 1, wherein: said vertex angle is greater than or equal to 30° and less than or equal to 180°; andsaid distal sensing end has a cleanable surface area that is greater than or equal to 1 cm2 and less than or equal to 20 cm2. 11. The cleanable conductivity sensor of claim 1, wherein said vertex region comprises a notch configured to receive a rotatable drive shaft in a tight-fit configuration. 12. The cleanable conductivity sensor of claim 1, wherein said distal sensing end has a surface shape that is a portion of a circle having a ratio of cleanable surface area to distal sensing end surface area that is greater than or equal to 80%. 13. The cleanable conductivity sensor of claim 1, wherein said outer fin dimensions are selected to provide an electric field in said conductivity measurement cell volume that is independent of presence or absence of a sensor guard that encloses said distal sensing end. 14. The cleanable conductivity sensor of claim 1, wherein: said electrodes are separated from an inner surface of said outer fin by a fin-electrode separation distance;said outer fin has an outer fin height; anda ratio of said outer fin height to said fin-electrode separation distance is greater than or equal to 2.4. 15. The cleanable conductivity sensor of claim 1, having an outer fin height that is greater than or equal to 1 mm and less than or equal to 5 cm. 16. The cleanable conductivity sensor of claim 1, further comprising a sensor guard having a plurality of openings to surround said distal sensing end and said outer fin. 17. The cleanable conductivity sensor of claim 16 wherein said outer fin is adjacent to an inner surface of said sensor guard and said sensor guard comprises one or more fluid sample openings for fluid sample introduction from a fluid environment outside said sensor guard to said conductivity measurement cell volume. 18. The cleanable conductivity sensor of claim 17, having a guard separation distance between said outer fin and said sensor guard inner surface that provides a tight-fit that substantially prevents biological growth between said outer fin and said sensor guard inner surface, wherein said guard separation distance is less than 1 mm. 19. The cleanable conductivity sensor of claim 16, having a ratio of conductivity measurement cell volume to a sensor sensing volume that is greater than or equal to 0.0001 and less than or equal to 0.1. 20. The cleanable conductivity sensor of claim 16, wherein said plurality of electrodes are open to a sensor sensing volume. 21. The cleanable conductivity sensor of claim 20, wherein said plurality of electrodes comprise two drive electrodes and two sensing electrodes, cleanable conductivity sensor further comprising a temperature sensor having a temperature sensing surface that is coincident with or proximal to said distal sensing end. 22. The cleanable conductivity sensor of claim 20, wherein a sensor sensing volume is defined by an inner surface of said sensor guard that encloses said cleanable conductivity sensor, said sensor sensing volume is greater than or equal to 0.5 mL and less than or equal to 100 mL, and wherein said conductivity measurement cell volume is defined by an outer fin separation distance from said vertex region, an outer fin height, and a length of said outer fin height. 23. The cleanable conductivity sensor of claim 1, that provides long-term, high-fidelity conductivity sensing without having to remove said cleanable conductivity sensor from a measurement environment and/or without active maintenance, characterized by a measurement accuracy that is within 0.5% for an operating time of at least six months. 24. The cleanable conductivity sensor of claim 1, wherein said outer fin minimizes a conductivity interference from objects located outside said conductivity measurement cell volume, wherein said minimizes conductivity interference corresponds to a decrease in conductivity interference by at least 50% compared to an equivalent cleanable conductivity sensor without said outer fin. 25. A cleanable conductivity sensor comprising: a substantially planar distal sensing end comprising: a vertex region;a first inner end edge extending from said vertex region to a first inner end point;a second inner end edge extending from said vertex region to a second inner end point, wherein said first inner end edge and said second inner end edge extend in directions to define a vertex angle;an outer end edge that extends between said first inner end point and said second inner end point;an outer fin extending from said distal sensing end and positioned adjacent to at least a portion of said outer end edge to define a conductivity measurement cell volume; anda plurality of electrodes having a distal end positioned at or proximate to said distal sensing end and between said outer fin and said vertex region to measure conductivity in said conductivity measurement cell volume;wherein said vertex region comprises a notch configured to receive a rotatable drive shaft in a tight-fit configuration;wherein the cleanable conductivity sensor is part of a multi-parameter sonde and further comprises:a first flat-faced inner surface that terminates at said first inner end edge;a second flat-faced inner surface that terminates at said second inner end edge; wherein said distal sensing end forms a portion of a circle;one or more additional sensors, wherein each additional sensor has a distal sensing surface; a first flat-faced inner surface and a second flat-faced inner surface extending from a vertex region that comprises a notch; and a curved outer surface that extends between said one or more additional sensors first flat-faced inner surface and said second flat-faced inner surface;in combination, said conductivity sensor and said one or more additional sensors form a single continuous sensing surface having a circular outer circumference in a single plane with a central orifice comprising said notches of said vertex regions;a rotatable drive shaft positioned in said central orifice;a wiper operably connected to said rotatable drive shaft and in rotatable contact with said single continuous sensing surface for cleaning a sensor portion of said single continuous sensing surface during use and a cleanable surface area of said cleanable conductivity sensor; anda sensor guard having a sensor volume that contains said continuous sensing surface and wiper. 26. The cleanable conductivity sensor of claim 25, wherein said wiper comprises: a central body having a downward-facing surface and an upward facing surface;a lower wiper connected to said downward-facing surface for rotatably contacting said sensor portion of said single continuous sensing surface;an upper wiper connected to said upward-facing surface for rotatably contacting a downward-facing surface of said sensor guard; andwherein said lower wiper has a lateral dimension that corresponds to an outer fin separation distance and said upper wiper has a lateral dimension to rotatably contact substantially all of said sensor guard downward-facing surface. 27. The cleanable conductivity sensor of claim 25, wherein the one or more additional sensors are selected from the group consisting of: a dissolved oxygen sensor, oxygen-reduction potential sensor, pH sensor, pressure sensor, turbidity sensor, ion sensor, temperature sensor, and sensor blank. 28. A method of making a cleanable conductivity sensor comprising the steps of: enclosing a plurality of electrodes in a wedge-shaped sensor housing having a substantially planar distal end that is coincident with or proximate to a distal end of each of said plurality of electrodes, wherein the wedge-shaped sensor housing has a curved outer surface that corresponds to a portion of a circle, a vertex region, and a first inner edge and a second inner edge extending from said vertex region and extending to a first inner end point and a second inner end point, wherein the curved outer surface extends between the first inner end point and the second inner end point; wherein said plurality of electrodes distal ends, said vertex region, said first inner edge, said second inner edge, and said curved outer surface form a single plane;positioning an outer fin adjacent to said curved outer surface and that extends along at least a portion of a lateral length of said curved outer surface, wherein said outer fin extends from said sensor housing distal end by an outer fin height;positioning an inner fin in a parallel configuration to said outer fin and separated from said outer fin by a fin separation distance, wherein said plurality of electrode distal ends are positioned between said outer fin and said inner fin, and said inner fin has a lateral length that is less than a lateral length of said outer fin, wherein said inner fin extends from said sensor housing distal end by an inner fin height; andproviding a rotatable wiper having a cleaning surface in rotatable contact with said sensor housing distal end between said outer fin and said inner fin;thereby making said cleanable conductivity sensor. 29. The method of claim 28, wherein said rotatable wiper is automatically engaged to clean said sensor housing distal end between said inner fin and said outer fin by rotation of said cleaning surface relative to said sensor housing distal end. 30. A method of making an accurate conductivity measurement in a liquid comprising the steps of: providing a multi-parameter sonde comprising a cleanable conductivity sensor and at least one additional sensor, wherein the cleanable conductivity sensor comprises: a substantially planar distal sensing end comprising: a vertex region;a first inner end edge extending from said vertex region to a first inner end point;a second inner end edge extending from said vertex region to a second inner end point, wherein said first inner end edge and said second inner end edge extend in directions to define a vertex angle;an outer end edge that extends between said first inner end point and said second inner end point;an outer fin extending from said distal sensing end and positioned adjacent to at least a portion of said outer end edge to define a conductivity measurement cell volume; anda plurality of electrodes having a distal end positioned at or proximate to said distal sensing end and between said outer fin and said vertex region to measure conductivity in said conductivity measurement cell volume;wherein active sensing elements of the sensors are coincident with a single continuous distal sensing surface;wherein said plurality of electrodes distal ends, said vertex region, said first inner end edge, said second inner end edge and said outer end edge form a single plane;rotably connecting a wiper to said single continuous distal sensing surface, including the cleanable conductivity sensor portion between an inner fin and the outer fin;enclosing the single continuous distal sensing surface and the wiper in a sensor guard having one or more openings;inserting the multi-parameter sonde into a liquid environment;periodically rotating the wiper over the single continuous distal sensing surface to clean the single continuous distal sensing surface without removing the multi-parameter sonde from the liquid environment; andmeasuring a conductivity parameter with the conductivity sensor,thereby making an accurate conductivity reading in a liquid. 31. The method of claim 30, wherein said conductivity sensor performance is independent of position of said one or more openings relative to said conductivity sensor.