NOBSKA Development Corporation

Industry leader in 3D Acoustic Current Measurement

MAVS Acoustic Current Meter
MAVS-3 Vector Averaging 3 Axis Acoustic Current Meter with Long Term Deployment capability

The MAVS (Modular Acoustic Velocity Sensor) Current Meter is a true 3 axis 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.
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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 standard range of measurement is 200 cm/sec, low speed measurement accuracy in the 0.03 cm/sec to 10 cm/sec range is preserved.

MAVS-3 includes MAVSOFTWin95, Win98, WinNT user interface. Standard, commercially available software such as Hyperterminal or Crosscut may be used to communicate with the MAVS-3for getting real time data or for downloading and archiving recorded data to a PC. Software such as MATLAB, Excel, Quattro Proand Lotus 123 may be used for tabular display and graphing data

The MAVS-3 employs a faired sensor head design with central strut and a 9.5 cm acoustic path length. The controller is an Onset Tattletale 8 which is mounted by a connector beneath the main circuit board. A battery pack comprising 18 AAalkaline cells provides all the necessary power to the instrument. A4 pin connector mounted on the top end cap permitsexternal power to be applied and provides TTL level, RS-232 or RS-485 communication capability.
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The differential travel-time technique is uniquely effective for velocity measurements in the ocean where there may be too few scatterers for reliable small-scale velocity measurement by acoustic Doppler scattering. Despite the convenience of a remote sensing volume, the fixed sampling volume of the acoustic travel-time sensor has advocates, particularly when used near boundaries. And finally, the extreme resolution in velocity is valued for some applications, particularly for very low current speeds.

MAVS Operating Manual

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• Unsurpassed resolution and accuracy
• True 3 axis acoustic velocity measurement
• Field proven sensor technology
• No moving parts to foul
• Multi-mode operation, vector averaging
or event driven sampling
• Excellent vertical cosine response
• Differential travel time measuring
• Internal recording or direct reading
• Accuracy unaffected by instrument tilt
or mooring motion
• Internal real time clock
• Digital communication via 5 Volt TTL,
RS-232 or RS-485
• Temperature measurement
• Direct Reading: RS-232 or RS-485
• Power: 10-15 Volts DC



0.3 cm/sec
+/- 2 deg
0.1 deg
0.1% FS
0.04% FS
2 deg


-5 to 45

0.03 cm/sec
0.1 deg
0.03 deg
0.024% FS
0.024% FS
0.1 deg
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Drift: 0.15 cm/sec per month

Measurement Technique: Differential travel time, 3 axis

Acoustic Paths: 4 measured, 4 used


Internal Recording: 13.5 VDC, 18 AA Alkaline batteries, @ 4.8 Ah,
optional lithium thionyl chloride 14.4 VDC @ 8.8Ah
Direct Reading: External 12-15 VDC
Current Drain: 23 ma. Measuring
0.6 ma. Sleep Mode

Internal Recording Memory: 16, 32, 48, 64, 96, 128, 160, 192, 256, 300, 512 Mbyte compact flash card

Memory Usage: Dependent on sampling method and size of memory installed

Communications: TTL, RS-232 or RS-485 @ 38,400 baud maximum 115.2 K baud

Depth: 2,000 m. or 6,000 m.

Cylinder Diameter: 3.25 in.
Overall Length: 25 in.

Water: 2.6 lbs.
Air: 5 lbs.

Mooring Frame: 2000 lbs. Optional 10,000 lbs. available

Sampling Rates: 10 Hz in Earth Coordinates (resolved to Ve, Vn, Vup) or
15 Hz in instrument coordinates
25 Hz Raw Data, No Compass, No Options

Sea Cable: RS-485 or RS-232 4 wire (inquire for other communication protocols)

Data Record Size:
Standard Instrument: 32 bytes per record for Day, Hour, Min, Sec, T, Tilt, Ve, Vn, Vu

Recorded as Binary and transmitted as ASCII Comma separated variables with CR LF

Operating Modes: Vector Averaging
Burst Mode (programmed for timed sampling)
Externally Triggered Sample
Continuous Sampling

Software: MAVSOFTWindows95, Windows98, Windows XP NTuser interface
Terminal Emulator: Hyperterminal, Crosscut or Tattleterm
Optional Graphical Software available upon request

All Product Include the Following Software:
• MWAVES Software for Plotting Directional Wave Spectra
• MAVSOFT GUI Interface Software for Pre-Deployment Setup, Post-Deployment Data Offload and MAVS Calibration

MWAVES Operating Manual
Available Options:
• Tilt Sensor
• External Temperature Sensor
• Conductivity Sensor
• Pressure Sensor
• Turbidity Sensor
• Deep Water Housing
• Compact Flash logging memory
available from 8 to 300 Mbyte
• Analog Output 4 Channel
Optional sensors available upon request.

click here to view a complete list of products and options.