Aanderaa ZPulse Doppler Current Sensor DCS 4420/4520

Application Note: Upgrading the Nagoya Seaberth System with Accurate Current Flow & Directional Monitoring in Real-Time

The ZPulse Doppler Current Sensor (DCS) is a singlepoint current sensor primarily intended to be used with the Aanderaa SeaGuard platform to form a Recording Current Meter (RCM).

  • Features
  • Specifications

The ZPulse Doppler Current Sensor (DCS) is a rugged, true vector-averaging sensor for measuring current speed and direction in the sea. 

ZPulse (DCS) Doppler Current Sensor

  • Unique ZPulse multi-frequency acoustic technology improves data quality, sampling speed and reduces power consumption
  • Smart sensor for easy integration on the SeaGuard platform
  • Built in solid state three axis tilt compensated compass
  • Direct readout of engineering data
  • Fast sampling rate
  • Low power consumption
  • Insensitive to fouling
  • Low maintenance needs
  • DCS 4420 / DCS 4520 / DCS 4830 / DCS 4930 model: AiCaP and RS-232 output
  • DCS 4420R / DCS 4520R / DCS 4830R / DCS 4830R model; RS-422 output
  • DCS 4830 / DCS 4930 / DCS 4830R / DCS 4930R including temperature

The Aanderaa DCS Doppler Current Sensor is a singlepoint current sensor primarily intended to be used with the Aanderaa SeaGuard platform to form a Recording Current Meter (RCM). It is designed for commercial as well as research use. There are 8 versions; 4420/4420R, 4830/4830R has a depth rating of 300 meters, while the 4520/4520R/ 4930/4930R has a depth rating of 6000 meters. 4830/4830R/4939/4930R have a temperature sensor included.

4420/4520/4830/4930 has both AiCaP and RS-232 ouput. The SeaGuard platform and the smart sensor are interfaced by means of a reliable CANbus interface (AiCaP), using XML for plug and play capabilities. 4420R/4520R/ 4830R/4930R has only RS-422 output for use as stand-alone sensor with long cables. The sensor version must be specified when ordered as the versions are not interchangeable. The R-version can not be used in SeaGuardapplications.

Specification 4420 4520 4830 4930
Shallow Water yes yes
Intermediate Water   yes yes
Deep Water   yes yes
AiCaP1 yes yes yes yes
RS-232 yes yes yes yes
In-line
Temperature   yes yes
Z-Pulse4 yes yes yes yes
Profiler
Single point yes yes yes yes
1 The Seaguard platform and the smart sensor are interfaced by means of a reliable CANbus interface (AiCaP), using XML for plug and play capabilities.
2 RS-422 output for use as stand-alone sensor with long cables.
3 Optional Temperature sensor 4080 available
4 ZPulse technology which improves the statistical precision. Complex acoustic pulses comprising several distinct frequencies are combined into a single acoustic pulse. The ZPulse based DCS separates the received signal into different frequency bands, one for each frequency in the transmitted signal. Further it analyses the frequency shift using a high speed Digital Signal Processor using an ARMA based parametric model processing algorithm to find the Doppler shift frequencies. This multi-frequency technique reduces the required number of pings needed in order to achieve an acceptable statistical error. The achieved measurement precision is proportional to the inverse of the square root of the number of ping measurements in a measurement interval. The ZPulse DCS uses two frequencies and this gives a reduction by a factor square root of two compared to a single frequency sensor. A single frequency sensor needs twice the number of ping to achieve the same precision as the Zpulse DCS.

The Aanderaa DCS sensors are based on the backscatter acoustic Doppler principle. The DCS has two orthogonal transducer axes with two transducers on each axis. This enables the DCS to measure in both directions on each axis which is a great advantage. This makes it insensitive to disturbance from vortex speeds around the sensor itself and the mooring line when the forward ping feature is enabled. One transducer on each axis transmits short ultrasonic pulses simultaneously. The same transducers receive backscattered signals from particles in the water. This gives an orthogonal x and y speed component which is tilt compensated to find the correct horizontal speed components.

The North and East speed components are calculated based on the x and y speed components and the heading from the built-in solid state electronic compass. The sensor takes several of these two-component measurements and finally calculates the averaged north and east speed components and the vector averaged absolute speed and direction.

Another great advantage is the new Aanderaa ZPulse technology which improves the statistical precision. Complex acoustic pulses comprising several distinct frequencies are combined into a single acoustic pulse. The ZPulse based DCS separates the received signal into different frequency bands, one for each frequency in the transmitted signal. Further it analyses the frequency shift using a high speed Digital Signal Processor using an ARMA based parametric model processing algorithm to find the Doppler shift frequencies. This multi-frequency technique reduces the required number of pings needed in order to achieve an acceptable statistical error. The achieved measurement precision is proportional to the inverse of the square root of the number of ping measurements in a measurement interval. The ZPulse DCS uses two frequencies and this gives a reduction by a factor square root of two compared to a single frequency sensor. A single frequency sensor needs twice the number of ping to achieve the same precision as the Zpulse DCS.

The solid state sensor is well suited for monitoring low current speeds due to no moving parts. Because the sensor starts measuring in an area 0.4 to 1.0 meter from the instrument, the effect of marine fouling and local turbulence is minimized.

Aanderaa ZPulse DCS Doppler Current Sensor Head

Specification
Current Speed (Vector Averaged)
Range 0 to 300cm/s 
Resolution 0.1mm/s 
Mean Accuracy ± 0.15cm/s
Relative ± 1% of reading
Statistical percision (std) 0.3cm/s (ZPulse mode),
0.45cm/s1
Current Direction
Range 0 to 360° magnetic
Resolution 0.01°
Accuracy ±5° for 0-15° tilt
±7.5° for 15-35° tilt
Temperature
(only 4830/4830R/4930/4930R)
 
Range  -5°C to +40°C
Resolution 0.01°C
Accuracy 0.1°C
Setting Time 30s
Tilt Circuitry
Range 0-35°
Resolution 0.01°
Accuracy ±1.5°
Compass Circuitry
Resolution 0.01°
Accuracy ±3°
Depth Capability
4420 / 4420R 300m
4520IW / 4930IW 2000m
4520DW / 4930IW 6000m

Notice: Specifications subject to change without prior notice.

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