Test and Evaluation Report For the Greenspan EC3000 Conductivity/Temperature Sensor.

Abstract

The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) maintains a suite of conductivity/temperature (CT) sensors on a select number of its National Water Level Observation Network (NWLON) and Physical Oceanographic Real-Time (PORTS®) stations. The data from these sensors can be used to calculate water salinity and density, which are important tools for safe navigation, especially in the determination of ship draft. Most CT sensors used on CO-OPS stations are manufactured by Falmouth Scientific, Incorporated (FSI). In a continued effort to explore evolving technology and to expand the suite of instruments available for operational use in its observatories, CO-OPS selected the Greenspan EC3000 CT sensor for test and evaluation. Before an instrument can be approved for operation on a CO-OPS platform, it must first undergo testing by CO-OPS’ Ocean Systems Test and Evaluation Program (OSTEP). OSTEP designed a series of laboratory and field tests to evaluate the performance of the Greenspan sensors under a variety of conditions. In one round of laboratory tests, both the FSI and Greenspan sensors were compared independently to a range of conductivity calibration standard solutions. In a second round of tests, the two sensors were tested concurrently in CO-OPS’ seawater test bath facility. In the first of two field tests, a Greenspan CT sensor was deployed at the Money Point, Virginia NWLON station; data from the instrument were compared to the operational FSI CT sensor at that location. In the second field test, a Greenspan CT sensor was deployed on a NOAA Chesapeake Bay Interpretive Buoy System platform and compared to a Sea-Bird SBE-52 CT sensor. In laboratory tests with conductivity calibration standards, the Greenspan results were more closely aligned with the standard solutions than the FSI results. However, several laboratory test design details were not ideal for the FSI, including the likelihood that the test container was too small for the sensor. The Greenspan and FSI conductivity and temperature readings were within manufacturer specifications during the seawater bath tests, even though results revealed possible issues due to edge interference and tank stratification. Improvements to the laboratory facility, such as a higher quality reference CT sensor, have been recommended. During field tests, the Greenspan compared more favorably to the FSI in conductivity (-0.01 versus -0.2 mS/cm) and more favorably to the Sea-Bird in temperature (-0.03 versus -0.4 °C). Some configuration problems were encountered with the Greenspan that delayed the test and evaluation schedule. However, representatives from Greenspan worked with OSTEP personnel to resolve these issues. As a result, the Greenspan CT sensor can now be integrated with a Sutron Xpert Data Collection Platform in an operational real-time CO-OPS observatory. Overall, Greenspan EC3000 data have compared very well with the data from the FSI and SeaBird. Based on test results reported here, the Greenspan EC3000 is recommended for use at operational CO-OPS observatories.