FSI Papers

7/13/06

Papers

DIGITAL OUTPUT TEMPERATURE SENSING MODULE FOR OCEANOGRAPHIC & ATMOSPHERIC MEASUREMENTS

Fougere, Brown, and Hobart.

The authors have developed a physically small high accuracy Temperature Sensing Module (TSM) for use in oceanographic and atmospheric temperature measurements. Using internally calibrated electronic measurement techniques to interface to a Platinum Resistance Thermometer (PRT) the development team was able to combine measurement, computation, and digital transmission electronics into a compact module. The TSM's operating system allows for continuous, polled, and calibration mode operation with calibration coefficients being stored in internal EEPROM. Data is output using one of several optional interfaces in ASCII encoded degrees Celsius. All temperature computations are performed by the embedded processor in the module. The unit attains both high initial accuracy and long term stability through the use of a newly developed pressure protected PRT. The PRT was developed specifically to meet the demanding requirements of environmental measurements under harsh conditions. System overview, test data, sensor data, and calibration results are presented.

INTEGRATED CTD OCEANOGRAPHIC DATA COLLECTION PLATFORM

Fougere, Brown, and Hobart.

The Mark III conductivity-temperature-depth (CTD) profiler has been the mainstay of modern physical oceanographic research. The MKIIIB CTD provides high quality oceanographic data when used by skilled personnel and are frequently re-calibrated. The design objective of the Integrated CTD system was to attain the same high level of performance while reducing the necessity of frequent re-calibration through the enhancement of long term stability. This required re-consideration of both the electronic approach and the re-design of the physical sensors. The result of this work is a CTD system with improved measurement precision. All three primary sensors are newly designed to achieve long term measurement stability and to optimize system sampling performance without the limitations of existing technologies.

Advances in the state of the art in electronic and microcontroller technologies has enabled the development of improved methods of analog sensor signal processing. During the MKIII development, micro-processors and their software development tools were primitive and difficult to use. The revolution in high speed micro-controllers has allowed their use in the Integrated CTD allowing for real time numerical correction for drift in the analog signal processing circuitry.

MICRO-CTD INSTRUMENT DEVELOPMENT FOR THE OCEAN SCIENCES

Fougere, Brown, Frye and Toole

Scientists involved in climate related research problems are increasingly in need of long-duration measurements of ocean characteristics such as temperature and salinity. Available instrumentation for these tasks is severely limited by accuracy, power, long-term stability, and high cost. We have developed a very small, low cost, deployable CTD (the Micro-CTD) to meet these increasingly important needs. In addition to small size and high sampling speed, the Micro-CTD incorporates a new inductive conductivity sensor which is highly accurate and can be treated with an anti-foul coating to minimize the effects of bio-fouling. This is a major advantage for long duration observations over existing high accuracy conductivity sensors. Size and measurement performance of the instrument allow use with a wide variety of new sensing system platforms such as drifters and pop-up buoys. Micro-CTD architecture allows for either data storage or data telemetry by acoustic, inductive, or hardwired telemetry. Paper covers system architecture, preliminary specifications and calibration data.
A SIMPLE LOW COST ACOUSTIC CURRENT METER, 1992

Brown.

This paper, written and presented by Neil L. Brown at Oceanology International in 1992 is the premise of all FSI acoustic current meter technology. Brown introduced an "experimental" acoustic current meter that would provide an alternative method to obtaining water current data.

A THREE DIMENSIONAL ACOUSTIC CURRENT METER (3D-ACM) update 1998

Brown, Fougere, and Kun.

Much has been learned about ocean dynamics by making measurements of ocean currents with traditional electromechanical type current meters. Flow distortion, large sample volumes, and impeller stalling, however; has limited the ability to use these instruments to make surface and wave deep ocean current measurements. New acoustic measurement techniques offer the potential to overcome these limitations. We present results of laboratory and field tests of a new, low power, acoustic phase shift current meter that transmits a 1 MHz acoustic signal along four paths and uses the along-the-path phase-shift measurement to resolve the three components of velocity.

APPLICATIONS OF AN ACOUSTIC CURRENT MEASUREMENT TECHNIQUE

Fougere and Kun.

Falmouth Scientific Inc. has a full range of instruments for measuring direction, velocity and, in the case of waves, directional and point spectra. These are the 3D-ACM, the 3D-ACM Wave, and the 2D-ACM. All three instruments use Falmouth Scientific’s acoustic current measurement technique, which is based on measuring and comparing direct path acoustic phase shifts along multiple paths. The technique has proven to provide high accuracy current measurements and its hardware implementation requires very low power.

COMMAND/STATUS TELEMETRY SYSTEM FOR USE IN CONJUNCTION WITH CTD INSTRUMENTATION SYSTEMS

Fougere and Smith.

Woods Hole Oceanographic Institution under NSF contract developed a control system to operate the WOCE large volume water sampler pump and valve systems. The operation of the control system requires the transmission of commands from the surface to the water sampler and corresponding transmissions of conformation and/or status data back to the surface. The telemetry system is required to operate in conjunction with commercially available Conductivity Temperature and Depth Profilers (CTD's) which also transmit their data over the same path (same conductor in the Electro-mechanical cable). This paper describes the development of a command/response telemetry system which allows for 1200 baud full duplex data communication to operate in unison with standard CTD profilers. The telemetry system utilizes advanced Digital Signal Processing (DSP) modems. These modems use digital equalization and demodulation techniques enabling the additional communication channel to operate via frequency subdivision techniques. The telemetry system also allows for communication with auxiliary instruments used in conjunction with the sampler, i.e., Altimeter.

NEW WAVE DIRECTION AND SPECTRUM MEASUREMENT TECHNIQUE

Kun and Fougere.

This paper describes a new measurement technique for wave spectrum and direction determination. The proposed technique combines acoustic current meter measurements with measurements from high precision pressure sensors. This technique allows the user to measure surface wave amplitude and direction, along with tide and tidal flow, from a single subsurface instrument. If the single instrument is combined with three additional "synchronized" pressure sensors, a complete six-wire-equivalent wave measurement can be attained.

COASTAL PREDICTIVE SKILL EXPERIMENTS: At Littoral Laboratory, Data-Assimilative Forecast Model Linked to Adaptive Multiplatform Network Being Evaluated

Glenn, Scott M.; Haidvogel, Dale B.; Schofield, Oscar M.E.; von Alt, Christopher; Levine, Edward R.. "Coastal Predictive Skill Experiments" Sea Technology Magazine. April 1998. (pp. 63 - 69).

An article detailing a series of coastal predictive skill experiments to be conducted at the Rutgers University Long-Term Ecosystem Observatory. Sensors used include a towed undulating vehicle with Falmouth Scientific, Inc. 3" Micro Conductivity, Temperature, Depth Sensor.

NEW NON-EXTERNAL FIELD INDUCTIVE CONDUCTIVITY SENSOR (NXIC) FOR LONG-TERM DEPLOYMENTS IN BIOLOGICALLY ACTIVE REGIONS

Fougere.

This paper, describing FSI's Non-External Field Inductive Conductivity Sensor, was presented at Oceans 2000 in Providence, RI, in September 2000. Long-term deployment of conductivity sensors in biologically active ocean regions normally results in poor conductivity data due to volumetric changes in cell geometry from biological fouling. Traditional inductive sensors allow anti-foulants to coat the entire sensor; this technique is highly successful when using newly developed materials, which have high mechanical stability. Alternately, some success has been achieved using internal field electrode sensors with the ends protected using anti-foulant impregnated tubes. These conductivity sensors have had limited success due to the basic instability of the sensor to fouling, biological or mineral, of the electrodes. This problem is further hampered by the very small internal geometry, which has enhanced sensitivity to fouling with combined poor natural flushing characteristics. However, in some applications, pumps have been applied to correct sensor aspiration. Pumps dramatically increase the power requirements, complexity, and cost of the system. FSI has developed a new inductive conductivity sensor with no external electrical/magnetic field--the Non-External Field Inductive Conductivity Sensor (NXIC). The NXIC sensor allows for the use of end tube leaching protection without the disadvantages of a conductivity sensor that does not flush freely or has an unstable calibration due to degradation of electrodes from fouling. The NXIC sensor has been fully developed and is now undergoing extensive laboratory and field-testing.An article detailing a series of coastal predictive skill experiments to be conducted at the Rutgers University Long-Term Ecosystem Observatory. Sensors used include a towed undulating vehicle with Falmouth Scientific, Inc. 3" Micro Conductivity, Temperature, Depth Sensor.
NEAR-REAL-TIME WAVE/CURRENT SYSTEM

Duchesney, Lassiter, and Phillips.

Falmouth Scientific, Inc. (FSI), Cataumet, Massachusetts, USA, and Geofix, Florida, USA have developed and installed a system to monitor ocean waves and other data from a remote location, using off-the-shelf components. The system monitors ocean currents, temperature, tides and waves. Monitored variables are measured in near-real-time with data sent via a hybrid radio telemetry link to shore. This data provides the local port authority with information to pass to ships navigating entrance to the port and to determine when it is safe for ships to enter or leave the port.
ULTRA DEEPWATER FLOATING PRODUCTION FACILITY FOR MAKASSAR STRAIT

Pradnyana and Korloo

Accelerometer monitoring for VIV on risers.