Accurate Flow-Through Conductivity Sensor for Autonomous Systems
Navy STTR 2018.A - Topic N18A-T022
ONR - Mr. Steve Sullivan -
Opens: January 8, 2018 - Closes: February 7, 2018 (8:00 PM ET)


TITLE: Accurate Flow-Through Conductivity Sensor for Autonomous Systems


TECHNOLOGY AREA(S): Battlespace, Electronics, Sensors

ACQUISITION PROGRAM: Program Office for Unmanned Maritime Systems Office (PMS 406); PMW-120 for the LBS-AUV(S) POR

OBJECTIVE: Leverage recent advances in nanotechnology and computational fluid dynamics as well as micro-fluidics, three-dimensional printing and specialized high-slip, fouling-resisting coatings to create major power, weight, and space savings for a conductivity sensor.

DESCRIPTION: Autonomous underwater vehicles and Lagrangian floats used by the Navy must carry conductivity, temperature and pressure for depth (CTD) sensors to support their missions in providing environmental data on the thermohaline structure of the ocean.  The data support forecast systems and tactical tools.  The present generation of flow-through sensors is bulky and power-intensive and prone to fouling by marine organisms, thus compromising performance.  The commercial generation of flow-through (versus pumped) sensors have a known tendency to have stability issues and thus compromise accuracy, which limits the lifetime and persistence of the systems for the Navy’s intended use.  Significant savings in cost for medium volume flow CTDs could be realized by injection molding, 3-D printing or other high-volume, rapid production techniques.  Engineered polymers that reduce weight without compromising ruggedness could bring major benefits.  Reducing the Size, Weight, and Power (SWaP) of commercially available devices while maintaining or increasing the stability and accuracy of the conductivity and pressure sensor will enable a power savings by a factor of five to seven times without reducing useful lifetime.  The commercial market could benefit by partnership with universities to take advantage of computational fluid dynamics modeling, micro-fluidics, and specialty surface coatings to achieve this goal.

This topic seeks a prototype conductivity, temperature, and pressure sensor that requires no pump system; and is low-power and stable for up to three to five years (the approximate lifetime of present profiling float systems).  The major challenge is adequate stability and accuracy in the conductivity sensor.  A target cost per unit is less than $1,000.  Desired specifications are the following:

For long-life devices that contribute data to the Argo program, the Argo standards should apply.

The temperatures should be accurate to ±0.002°C and depth via pressure accurate to ±2.4dbar.  Salinity derived from conductivity has been the challenge because the data are affected by sensor drift – where drift is small the uncorrected salinities have been accurate to ±0.01 psu.

This STTR topic is directed at short-life systems that profile more rapidly; for these systems we believe the threshold for performance should be the following:
Depth (Pressure) Parameter: Range 1000db; Accuracy ±0.1% full scale; Resolution 0.01% full scale; Stability 0.1% full scale/year
Temperature Parameter: Range -5°C to 35°C; Accuracy ±0.02°C; Resolution 0.0005°C; Stability 0.01°C/year
Conductivity Parameter: Range 0 to 85mS/cm; Accuracy ±0.03mS/cm; Resolution 0.01mS/cm; Stability 0.10mS/cm/year

Ultimately, the objective of the new sensor would meet the Argo standards [References 2, 3].

PHASE I: Provide a trade-off study of the parameters and cost for an initial prototype design.  Develop a Phase II plan to create a prototype.

PHASE II: Based upon the results of the Phase I design, develop and deliver a prototype sensor.  Support extensive (up to six months) tank testing in a range of conditions with an initial at-sea test.

PHASE III DUAL USE APPLICATIONS: Ruggedize and mature the sensor for installation, integration, and at-sea testing, and implement cost reduction measures to provide a minimal-cost product for Navy acquisition.  Consider methods to reduce the power of the device.

This technology could be used by small profiling floats, gliders, Unmanned Surface Vehicles (USVs), and Unmanned Underwater Vehicles (UUVs).


1. Janzen, C. “Improving CTD Data from Gliders by Optimizing Sample Rate and Flow Past Sensors.”  Ocean News and Technology 2011 (17(7): 22-23).

2. Oka, E. and Ando, K. “Stability of Temperature and Conductivity Sensors of Argo Profiling Floats.” Journal of Ocean Engineering 2004. Vol. 60, pp. 253-258. DOI 10-23/B:JOCE.0000038331.10108.79.

3. Barker, P. M., Dunn, J. R., Domingues, C. M., and Wijffels, S. E. “Pressure Sensor Drifts in Argo and Their Impacts.” Journal of Atmospheric and Oceanic Technology 2011, Vol. 28, pp. 1036-1049.

4. Abraham, J. P., Baringer, M., Bindoff, N. L., Boyer, T., Cheng, L. J., Church, J. A., Conroy, J. L., Domingues, C. M., Fasullo, J. T., Gilson, J., Goni, G., Good, S. A., Gorman, J. M., Gouretski, V., Ishii, M., Johnson, G. C., Kizu, S. Lyman, J. M., Macdonald, A. M., Minkowycz, W. J., Moffitt, S. E., Palmer, M. D., Piola, A. R., Reseghetti, F., Schuckmann, K., Trenberth, K. E., Velicogna, I., and Willis, J. K. “A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change.” Reviews of Geophysics 2013, Vol. 51(3), pp. 450-483.;jsessionid=EACF24A43864BD4E220C7D48A085A6E5.f02t01

KEYWORDS: Conductivity Sensor; Accuracy; Flow-through; Low Power


These Navy Topics are part of the overall DoD 2018.A STTR BAA. The DoD issued its 2018.A BAA SBIR pre-release on November 29, 2017, which opens to receive proposals on January 8, 2018, and closes February 7, 2018 at 8:00 PM ET.

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