RAPID-MOCMooring Array Instrumentation Instrument types and specifications Telemetry

CTD and current profilers (MMP and HOMER)Fixed point CTD (SBE 37 - microCAT)Current meters (S4)Tide gauges or bottom pressure recorders (SBE 26)

Test instruments

Instruments

How did we choose?

Satisfy the sensor specification and accuracy that we specified

Reliable Robust Simple to use

SBE 37-SM The SBE 37-SM MicroCAT is a high-accuracy conductivity and temperature (pressure optional) recorder with internal battery and memory. Designed for moorings or other long duration, fixed-site deployments.

Pump: The submersible pump comes on for 0.5s for each sample.

This improves the conductivity response and flushes the old sample from the cell

Water does not flow between samples allowing the anti-foul concentration to build up protecting the cell.

SBE 37-SM Specification

Range Accuracy Stability Resolution

ConductivitymS/cm

0 to 70 0.003 0.0003 0.0001

Temperature °C -5 to 35 0.002 0.0002 0.0001

Pressure dbar 0-35000-7000

0.1% fs 0.004% fs 0.002% fs

Battery capacity is 80,000 samples (9/hour for 1 year)

SBE 26 SEAGAUGE Wave & Tide RecorderThe SBE 26 continuously integrates pressure samples to obtain water level measurements unaffected by wave action, and also independently burst-samples pressure at rates up to 4 Hz for wave amplitude calculation. Water level integration and wave burst sampling intervals and durations are programmable. The large memory permits frequent water level recording and highly detailed wave characterization. For example, with an 8M byte memory and optional lithium batteries, a 120-day deployment could include water level measurements every 15 minutes and 20-minute, 2 Hz wave-burst samples eight times a day.

SBE 26 SEAGAUGE Wave & Tide Recorder

Temperature(°C)

Pressure

Measurement Range -5 to +35 13 ranges, from 0 to 1 m (15 psia) to 0 to 6800 m (10,000 psia)

Accuracy 0.02 0.01% of full scale (3 mm for 45 psia range)

Resolution 0.01 Tide:0.2 mm (0.008 in.) for 1-minute integration;0.01 mm (0.0004 in.) for 15-minute integration

Calibration +1 to +32 0 psia to F.S. Pressure

Repeatability 0.005% of full scale (1.5 mm for 45 psia range)

Hysteresis 0.005% of full scale (1.5 mm for 45 psia range)

S4 Current Meter by InterOcean

The S4 Electromagnetic Current Meter measures the voltage resulting from the motion of a conductor (water flow velocity) through a magnetic field according to Faraday's law of electromagnetic induction. Simply stated, Faraday's law defines the voltage produced in a conductor as the product of the speed of the conductor (water flow velocity) times the magnitude of the magnetic field times the length of the conductor. In the case of the S4, the conductor length is the effective path between the sensing electrodes. The magnetic field intensity is generated by a circular coil, internal to the S4, driven by a precisely regulated alternating current. The use of an alternating magnetic field and synchronous detection techniques to measure the voltage at the sensing electrodes provides an extremely stable, low noise current measurement. Two orthogonal pairs of electrodes and an internal flux gate compass provide the current vector.

Current Speed------------------------------------------------------------------------Range 0-350 cm/sec (standard)0-50, 0-100, 0-600, 0-750 cm/secAccuracy: 2% of reading +/- 1 cm/secSampling Rate: S4/S4AS4AH 2 Hz5 HzResolution: 2 Hz 0.03 to 0.35 cm/sec depending on range  5 Hz 0.037 to 0.43 cm/sec depending on rangeNoise: Less than the resolution for averages of 1 minute or longer0.05 cm/sec rms for 10 second averages0.25 cm/sec rms for 2 second averages0.75 cm/sec rms for burst sampling (0.5 second rate)Threshold: Equal to resolutionVertical Response: True cosine response (internally software corrected with Tilt option)------------------------------------------------------------------------Direction------------------------------------------------------------------------Type: Flux-gate compassRange: 0-360Resolution: 0.5 degAccuracy: +/- 2 deg within tilt angles of 5 degTilt: +/- 4 deg for tilt angles between 15 and 25 deg

S4 Specification

Profiling CTD and current meters

HOMER MMP

HOMER Bottom mounted package with a buoyant

capsule and CTD that is winched through the water column

Max depth 3000m Range 400 m from the bottom Velocity of buoy 0.3 m/s Capability: 1 profile per day for 1 year

MMP

The McLane Moored Profiler (MMP) is an autonomous, instrumented platform.

Designed to provide long time-series, in situ profiles of temperature, salinity, velocity, and other quantities of interest.

The commercial version, the MMP MK 7, is now in production at McLane Research Laboratories, Inc. (MRL).

The new design incorporates the proven features of the original prototypes, developed by the Advanced Engineering Laboratory of the Woods Hole Oceanographic Institution, in a package that is easily serviced in the field and robustly tolerant of typical shipboard conditions.

An all new MK10 is in development for SOC with new sensors and an inductive modem for telemetry.

DimensionsHeight   130.5 cmWidth   33.3 cmLength (body)   50.5 cm  Weightw/ Sensors (air)   70.5 Kg w/o Sensors (air)   64.3 Kg Max Depth   6,000 mEndurance   1Mm

MK10 modifications for SOC

SBE41 CP - SeaBird CTD as used in argo floats

SBE44 Inductive modem for real time data telemetry

Main changes: longer body, larger pressure case

Telemetry Developments by SOC

Specify new sensor and inductive system for MMP MK10 mercury swivels for electrical connectionsSurface buoy with rechargable batteries and solar cellsIridium and Orbcomm transmitters/receivers

Timescale Persistor computer system with power controller and Iridium interface is built and under

test. SeaBird SIM and UIM components have been purchased and will be integrated with the

Persistor once we know how the MMP is to control the data transfer. A prototype buoy hull has been delivered together with frameworks for the solar panels and

batteries. The solar panels and batteries are under test. A miniature GPS receiver has been purchased and tested. Outstanding work: Integrate Orbcomm communicator into system and test with new short antenna. Build electronics housing and antenna platform and integrate into buoy. Integrate SIM board and test data transfer from (simulated) MMP back to SOC. Integrate GPS receiver and antenna. Build and test battery and temperature monitoring circuits and integrate. Fit pressure relief valve to buoy hull. In early September it is planned to take the Persistor/Iridium/SIM subsystem to McLane in

the States (September 8th 2003) to check that it communicates successfully with the MMP.