NOBSKA

Model MAVS series
Modular Acoustic Velocity Sensor (MAVS)

The MAVS-2 Current Meter is a true three dimensional, high performance acoustic current meter which employs a differential travel time measurement technique. The current meter takes measurements across 4 acoustic axes to provide a true vector averaged velocity measurement. Programmable burst mode and triggered sampling provide the most flexible current meter available. The combination of small sensor geometry and differential travel time technique provide unsurpassed resolution and accuracy. The small transducer size significantly reduces the disturbance to water flow. While the range of measurement is 300 cm/sec, low speed measurement accuracy in the 0.03 cm/sec to 10 cm/sec range is preserved.

MAVS employs a faired sensor head design with central strut and a 9.5 cm acoustic pathlength. The controller is an Onset Tattletale 4A SBC which is mounted by a connector beneath the main circuit board. A battery pack comprising 15 AA alkaline cells provides all the necessary power to the instrument. A 4 pin connector mounted on the top end cap permits external power to be applied and provides TTL level or RS-485 communication capability. Optional sensors for Conductivity, Temperature, and depth measurements can be added.

Standard, commercially available software such as TTOOLS or PROCOMM may be used to communicate with the MAVS-2 for acquiring real time data or for downloading and archiving recorded data to a PC. Software such as Excel, Quattro Pro and Lotus 123 may be used for tabular display and graphing of data. Likewise, programs such as MATLAB may be used as well.

Configuration is done via an easy-to-use menu, and the instrument can be set to collect data from a rate of 2 to 50 Hz (not averaged) or 1 second to 15 min (vector averaged).

Processing of all data is carried out inside the instrument and the data are presented as numbers in engineering units.

The user has a choice of using the MAVS as an on-line system, or as a self-contained moored system with internal data logger. Storage capacity is dependent on configuration and we can provide a memory for data storage up to 2 Mbyte.

An optional external data logger and data acquistion system is available upon request. Storage capacity of 1.4 Gbyte and additional analog-to-digital inputs are also available for the external logger. The external logger is provided in a water tight shallow or deep ocean housing. This logger is ideal for tripod mounted ocean bottom measuring systems.



Faired Acoustic sensor head

Technical Specifications for MAVS-2

MAVS

Current velocity sensors
Range:   Programmable:± 300 cm/s  or: ± 600 cm/s 
Resolution: 0.03 cm/s,  0.06 cm/s at 600 cm/s range.
Accuracy: Normal operation ± 0.3 cm/s or 1% whichever is greater.



Temperature sensor
Range: -5 C to +45 C  
Resolution 0.015 C  
Accuracy: 0.25 C  
Response: <1s

Option:
Resolution: 0.01 C  
Accuracy: 0.02 C  
Response: 60 msec at flow rate 1 m/s

Pressure Sensor
Range: from 10 to 1500 dBar (Optional ranges available) 
Resolution:  0.1% FS  
Accuracy:  0.5% FS  
Drift: 0.7% TEB (0-50 C)
Response: 0.05 sec.

Conductivity sensor
Range: 2-75 mmho/cm  
Resolution: 0.02 mS/cm 
Accuracy: 0.2 mS/cm 
Response: 0.05 sec.

Fluxgate compass
Range: 0-360   
Resolution: 1   
Accuracy: ±2   
Response: 0.05 sec.

Tilt sensor
Range: 0-30   
Resolution: 0.1 deg.  
Accuracy: 2 deg.   
Response: 0.05 sec.

Depth capacity
Depth: 2000m, Option: 6000m

Communication
RS-232 is Standard
TTL or RS-485 is optional
Baud rate: 9600

FSK or SAIL @ 9600 baud (upon request)

Sea Cable
RS-485: 4 wire (inquire for other communication protocols)

Housing material
Cylinder: Aluminum

Dimensions (except connector)
Cylinder diameter: 3.0 inches O.D. 
Overall length: Standard unit 29 inches
 	 	 
Sampling frequency
2 Hz in Earth Coordinates (resolved to Ve, Vn, Vup) or 10 Hz in Instrument coordinates.
1 sec to 15 min vector average 
Up to 50 Hz (not averaged)


MAVS-2DL
Data logger capacity
Standard: 2 Mbyte
Optional: consult factory.
Optional: external data logger available using 1.4 Gbyte HDD

Data Record Size
12 bytes per record (no options installed)
Day, Hour, Min, Sec, T, T, Ve, Ve, Vn, Vn, Vu, Vu
Recorded as binary and transmitted as ASCII, comma separated variables with CR LF

Battery
Standard: 15 Alkaline AA
Direct Reading: External 24 VDC

Power consumption
Depending on programming of burst mode or averaging interval.

Weight
In air: 5 lbs.

In Line Mooring Tension (When Mooring Frame is purchased)
Standard: 500 lbs.
Optional: 5,000 lbs. or 10,000 lbs. (Specify when ordering)

For additional information on the MAVS current meter, please send e-mail to:

By Mail:
Dan Schaaf
NOBSKA
62 Musket Lane
Mashpee, MA 02649

Tel: 508-539-0404
Fax: 508-539-0808

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