Vessel Hardware

A Nortek VM current profiler system is comprised of the following three basic components :  

1.       A hull mounted current profiling transducer

2.       A power/communication interface unit

3.       A computer with multiple serial port

The system computer needs input  from the following external devices in order to correct for vessel motion and heading :

A.      DGPS  (vessel speed and direction over ground)

B.      Gyro    (vessel heading – there is no compass in the instrument)

C.      HPR    (heave-pitch-roll, optional)

D.      Attitude (optional)    

Transducer : 

The standard VMCP transducer, the VM AWAC, is available with either a bronze housing or an identically shaped body manufactured in Delrin plastic. In terms of functionality there are no differences between the two.

For long term permanent installations Nortek recommends the bronze housing, which has been developed in the tradition of marine standards.

The slightly lower priced Delrin housing will be a good alternative for less demanding applications over shorter intervals.  

The VM AWAC is available with either 1 MHz or 600 kHz acoustic system frequency. The 600 kHz version offers slightly longer range than the 1MHz, approx. 30 m vs. 20 m, whereas the 1 MHz units offer better accuracy and resolution.

Both units offer sufficient range to cover the depths of interest with respect to seismic streamer positioning, and the 1 MHz transducer has become the preferred model due to its advantages in measurement accuracy and resolution.     

Computer :

The supplied PC is a marine certified product with an IntelLGA Core 2 Dual (and solo) CPU. It is equipped with industrial grade components and built into a rugged rack mountable 19” chassis with  lockable front panel and removable flashdrive.

The computer is equipped with a multiple serial port which interfaces to DGPS, Gyro etc. and provides serial output data (e.g. speedlog) to other control systems onboard the vessel.   

Power/Interface Unit:

A power/interface unit is delivered with each transducer that is shipped from Nortek. The RS232/RS422 converter provides effortless communication between the hull mounted transducer and the instrument room, and the highly reliable and protected power supply is crucial in terms of reliable, uninterrupted operation.

System

Acoustic frequencies. Two models : 0.6 MHz and 1.0 MHz.

Acoustic beams: 3 beams slanted at 25°

Maximum ship speed: 20 knots 

Current profile

Maximum range: 40 m (600 kHz) or 25 m (1 MHz)

Depth cell size: 1-4 m (600 kHz) or 0.4-4 m (1 MHz)

Minimum distance to first cell: 2 m (600 kHz) or 0.6 m (1 MHz)

Maximum output rate: 1 Hz

Internal sampling rate: 3 Hz (600 kHz) or  8 Hz (1 MHz)

Number of cells: Typical 20-40, max. 128

 Velocity measurements

Velocity range: ±10m/s horizontal, ±5 m/s along beam

Accuracy: 1% of measured value ±5 cm/s

Resolution: 0.1 cm/s

Physical

Transducer housing material : Bronze or Delrin plastic/Titanium

Power

AC Input : 110/220 V AC, 50/60 Hz

Operating power consumption : 1-2 W

 Cable & Connectors

UW mateable, 4-pin Impulse connector.  

 Computer (optional)

Marine certified w/ Intel LGA Core 2 Dual (and solo) CPU. Industrial grade components, rack mountable 19” chassis with lockable front panel and removable flashdrive. The computer is equipped with a PCI multiple serial port. 

Interfaces

Interfaces to most popular DGPS’, Gyros and HRP sensors are available. In the unlikely event that we should not have the required interface in our library, Nortek typically offers to write a custom interface at no extra charge.