ZPulse® Doppler Current Sensor 4420/4520/4830/49300 pages

ZPulse® Doppler Current Sensor
4420/4520, 4420R/4520R
4830/4930, 4830R/4930R

A rugged, true vector-averaging sensor for measuring
current speed and direction in the sea.

Features ZPulse® Doppler Current Sensor:
•t Unique ZPulse® multi-frequency acoustic technology
improves data quality, sampling speed and reduces
power consumption.
•t Smart sensor for easy integration on the SEAGUARD®
platform.
•t Built in solid state three axis tilt compensated compass.
•t Direct readout of engineering data.
•t Fast sampling rate.
•t Low power consumption.
•t Insensitive to fouling
•t Low maintenance needs
•t 4420/4520/4830/4930 model: AiCaP and RS-232 output
•t 4420R/4520R/4830R/4830R model; RS-422 output
•t 4830/4930/4830R/4930R including Temperature
The ZPulse® Doppler Current Sensor (DCS) is a single-t
point current sensor primarily intended to be used
with the AADI SEAGUARD® platform to form a Recordingt
Current Meter (RCM). It is designed for commercial t
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 t
are inter- faced by means of a reliable CANbus interface t
(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 SEAGUARD® applications.
The DCS sensors are based on the backscatter t
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

AADI is a trademark of Xylem Inc. or one of its subsidiaries.

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 ZPulse® technology
which improves the statistical precision. Complex
acoustic pulses comprising several distinct frequencies t
are combined into a single acoustic pulse. The ZPulse®
based DCS separates the received signal into different t
frequency bands, one for each frequency in the
transmitted signal. Further it analyses the frequency
shift using a high speed Digital Signal Processor using ant
ARMA based parametric model processing algorithm
to find the Doppler shift frequencies. This multifrequency 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.

D367 - Feb 2012