NOBSKA Development Corporation

Industry Leader in 3D Acoustic Current Measurement

MAVS-4 Acoustic Current Meter
MAVS-4 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-4 includes MAVSOFT user interface for Windows Operating Systems and MAVSPack for easy transfer of data. 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 Pro and Lotus 123 may be used for tabular display and graphing data

The MAVS-4 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 AA alkaline cells provides all the necessary power to the instrument. A4 pin connector mounted on the top end cap permits external power to be applied and provides TTL level, RS-232 or RS-485 communication capability.

Direct reading 3 Axis Acoustic current measuring system (2000 or 6000 meters depth) includes:

  • RS-232
  • Compass 3-D
  • Tilt 3-D
  • Reusable transport case
  • Zinc anode
  • User's manual

*Optional hard coat anodized aluminum housing

MAVS Operating Manual
All MAVS-4 Instruments Include the Following Software:
• MAVSOFT GUI Interface Software for Pre-Deployment Setup, Post-Deployment Data Offload and MAVS Calibration

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


-5 to 45
70 deg.

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 deployment, less than 3 cm/sec per decade

Measurement Technique: Differential travel time, 3 axis

Acoustic Paths: 4 measured, 4 used

Power: Entry of Deployment Profile and Installed Battery Capacity provides Calculated Duration of Deployment Until Battery Becomes Discharged

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: 256MB, 300MB, 512MB, 1GB, 2GB compact flash card

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

Entry of Deployment Profile computes duration of deployment until Compact Flash is filled, based upon installed CF Sensed by MAVS.  Data Block Size is suggested for optimum usage of CF Boot Directory and Memory

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.
Housing Length: 25 in. (Aluminum or Titanium)
Sensor Length: 11 in. (Bent Sensor for MMP 18 in.)

* Short titanium housing option 8.65 in. length

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: MAVSOFT user interface is compatible with all Windows Operating Systems
Terminal Emulator: Hyperterminal, Crosscut or Tattleterm
Optional Graphical Software available upon request

Additional sensors connected to MAVS-4 measuring system:

Temperature, standard, internal sensor
Temperature, fast response, external sensor
Integration or RBR High Accuracy External Temperature Probe
Integration or RBR High Accuracy External Conductivity Probe

Accuracy: 0.5% FS 12 bit measurement
Range (dBar): 10, 30, 40, 100, 300, 1500, 3000, 6000
Other ranges available upon request.

Accuracy: 0.1% FS 12 bit measurement
Range (dBar): 10, 30, 40, 100, 300, 1500, 3000, 6000
Other ranges available upon request.

Accuracy: 0.04% FS 12 bit measurement
Range (dBar): 10, 30, 40, 100, 300, 1500, 3000, 6000
Other ranges available upon request.

16 bit Measurement available upon request

Electrical Integration of turbidity sensor
Additional Analog input channel for another type sensor
4 channel Analog output option
Cable for Analog Output Option
Bent Sensor Option for Horizontal Mounting of MAVS
MMP Bent Sensor for McLane Moored Profiler


Deep Water Housing
Compact Flash Logging Memory; 256MB to 2GB
RS-485 Option (4 Wire) for inside MAVS
Connector with 1 meter cable
O’Ring Spares Kit
Mooring and/or hanging frame, stainless steel, 2,000 lbs. load
Mooring and/or hanging frame, stainless steel, and 10,000 lbs. load
Tripod Mount for bottom mounting of one MAVS

Deck Unit / Lab Unit:
Communication Module for PC (RS-232 or RS-485)
Includes 110/220 VAC - 12 VDC Power supply and DB-9 comms
connector for connection to PC COM port. Ideal for use in either
Direct Reading or pre-deployment setup and offloading of archived
from internal memory.
RS-485 Option (4 Wire) for inside Deck Unit
Underwater cable between Deck Unit and MAVS

Acoustic Transmissometer Option
*Optional sensors available upon request.