AANDERAA

R CM 9
e
Th A unique
Recording Current Meter
for use in the sea
and in freshwater
featuring the Mark II
DOPPLER CURRENT
SENSOR DCS 3920
Measuring:
• Current Speed
• Current Direction
• Temperature

• Conductivity (optional)
• Instrument Depth (optional)
• Turbidity (optional)
• Oxygen (optional)
• Signal Strength (optional)
• Instrument Tilt (optional)
Stores data internally in the standard Data
Storage Unit DSU 2990 or transmits data in
real-time via cable.
Features:
- No offset
- Low noise
- Forward pinging algorithm
improves accuracy
- Insensitive to fouling
- No moving parts
- Easy installation and handling
- Easy functional verification using
an external Test Unit
Specially well suited for:
- Operation in the Wave Zone
- Monitoring Low Current Speeds

DATA SHEET, D 328, OCTOBER 2004 1 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

FIELDS OF APPLICATIONS
The instrument can be used in the sea, in oceans, in lakes and in rivers and its special technical features, such as the narrow
beam, compact design and type of integration makes it especially well suited for operation in the wave zone. An arctic temperature
range ensures proper operation in the Polar Regions.

In-line Mooring
The most common way to use the RCM 9 is in an in-line mooring configuration as shown below. As it operates under a tilt up to
35° from vertical, it has a variety of in-line mooring applications by use of surface buoy or sub surface buoy. The instrument is
installed in a mooring frame that allows easy installation and removal of the instrument without disassembly of the mooring line.
The illustration shows the so-called u-anchoring where retrieval of the instrument is done simply by pulling it on board the vessel
by means of the retrieval float and mooring line.

Direct Reading
Retrieval float The illustration to the left also shows
how the instrument can be used for
direct reading of current, temperature,
In-line mooring Direct reading and parameters such as conductivity,
turbidity, oxygen and instrument depth.
Viny Float set This is conveniently done due to its
compact design, low drag force and
easy handling. The instrument can be
lowered into the sea from a small boat
RCM 9
using a simple winch. In this applica-
RCM 9
tion a small vane plate should be fas-
tened to the instrument to avoid spin
during operation. Data can be stored
internally and read after retrieval or be
read in real time on deck by use of the
profiling cable. See also page 8.

Mooring Frame
The picture on page 3 shows the mooring frame for
RCM 9. Special mooring frame for the RCM is made to
facilitate easy installation and removal of the instrument
by use of two knobs.

A diver can accomplish deployment and retrieval. The

mooring frame is made ot stainless steel and has a
breaking load of 8000 kg. The frame is equipped with
a Sensor Protective Ring. RCM 9

Mooring Frame 3624

Additionally Protecting Rods 3768

Measurements on the Seabed Base Brackets 3627

The illustration to the right shows an RCM 9 placed on
RCM 9 in self leveling
the seabed. For the upper application, the frame must Mooring Frame 3438R

be furnished with two base brackets and placed on a Concrete Block

concrete block or similar.

The RCM 9 can also be mounted in a self-leveling

Frame 3438R, which makes the installation on the
seabed very easy.

One of these arrangements is often required for studying

the transportation of sediments and falling particles
from sea farm mares.

DATA SHEET, D 328, OCTOBER 2004 2 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

 AANDERAA INSTRUMENTS

Fastening Knobs

RCM Doppler Current Sensor

Protecting Rods

Mooring Frame

C-Clamp with Screw

Protecting Ring

Pressure Case

Zinc Anodes

DATA SHEET, D 328, OCTOBER 2004 3 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

GENERAL DESCRIPTION OF THE INSTRUMENT AANDERAA INSTRUMENTS

The development of a small, low power doppler current sensors The scattering particles are normally plankton, organisms
that has taken place in recent years, opens for many interesting and particles stemming from man-made activity. Near the sur-
applications. One of these is the RCM 9 MkII, a unique new face, gas bubbles are important scatterers. Thus the energy
self-contained instrument that can be moored in the sea for back-scattered and the usefulness of the instrument depends
long periods of time. In standard version it measures the horizontal on the presence of sufficient scatterers. These conditions will
current speed and direction, as well as temperature. Optional vary from place to place and significant seasonal variations
sensors are conductivity, turbidity of the water, dissolved oxygen are normally found in less polluted waters.
as well as instrument depth. Optional Output from the Doppler
Current sensor is Instrument Tilt and Signal Strength (you
need the recommended spares kit). Measuring area

The RCM 9 MkII utilizes the well-known Doppler shift principle

as the basis for its measurements. The system transmits an 0.4m 0.4m 1.8m
acoustic sinusoidal pulse at 2MHz. As the sound propagates
through the water, minute parts of its energy is reflected or
scattered by small particles in the water. This back-scattered Beam angle= 2°
RCM 9 MkII
energy is received by the system and analyzed to find any
change in frequency. An upward shift in frequency means
that the particles are moving towards the transducer and a
downward shift that the particles are moving away from the The instrument can operate continuously or in eight intervals
transducer. The degree of shift signifies the rate of movement. from 1 to 120 minutes. At 60-minute recording interval the
operating time is more than two years.
Assuming that the particles follow the currents in the water,
this system is used to monitor and determine the current The RCM Doppler Current Sensor is furnished with a new
speed and direction of the water. The direction is found by Hall effect compass and a two-axis tilt sensor that compensates
the use of measurements along two orthogonal axis and linking for the effect of inclination. This feature allows the instrument
them to true north by use of an internal compass reading. to be used in a mooring line with an inclination up to 35°
from vertical. The instrument has a depth capacity of 1000
meters. The current speed and direction are averaged over
the measuring interval.

The RCM Doppler Current Sensor on the instrument sends

out 150, 300 or 600 pings during each recording interval.
The pings are normally distributed equally in time over the
whole measuring interval but it is also possible to select a
Burst Mode.

When the instrument is moored near the sea surface, the

Burst Mode will reduce the influence of waves. In this mode
all pings are executed in the last minute of the measuring
interval.

Among the advantages of the RCM 9 MkII are its ease of deploy-
ment and that it has no moving parts. Even though the measur-
ing window of the DCS is between 0.4 to 2.2 meters from
the sensor itself, which minimizes the effect of marine fouling
and local turbulence, the current in the wake of the sensor
will be lower than the actual current. To avoid the error this
will have on the current measurement, a «Forward Pinging
Algorithm» has been introduced.

When the DCS samples a positive Doppler shift from one of

the transducers for the measurement in the X-axis, it will continue
to use this transducer for the measurement along the X-axis.
When the Doppler shift becomes negative, it will then change
to the opposite transducer, and so on. The same algorithm
is also applied for the Y-axis and the DCS toggles between
sampling in the two axis.

DATA SHEET, D 328, OCTOBER 2004 4 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

 AANDERAA INSTRUMENTS

The instrument is equipped with a watertight receptacle that fewer channels selected increases available DSU memory
enables external triggering and powering of the instrument for long deployments.
as well as real-time data acquisition via cable. The RCM 9 belongs
to a family of well proven oceanographic instruments that The standard sensors for this instrument are:
share a set of common features. They are all of simple and • Current Speed and Direction Sensor
sturdy design, they have low power consumption, they employ • Water Temperature Sensor
potted electronic circuits, and they have the same well proven Optional sensors are:
pressure case and same data storage units.The number of • Conductivity Sensor • Depth Sensor
sensors to be scanned can be set by a selector switch inside • Turbidity Sensor • Oxygen Sensor
the instrument. One can choose form 4 to 10 channels. The

Doppler Current Sensor 3920

This disk-shaped sensor has an OD of 120mm, is 45mm thick and has a
10-pin receptacle at its lower end. The sensor is fastened to the instru-
ment by an 86mm high sensor foot. Four piezoceramic acoustic trans-
ducers are placed 90° apart around the circumference of the sensor that
is molded in a polyurethane material.
The sensor utilizes the well-known Doppler Shift principle as the basis for
its measurements. The sensor transmits acoustic pulses of 2MHz into the wa-
Doppler Current Sensor 3920 ter in sequence. As the sound propagates, small particles or air bubbles
in the water reflect a portion of the energy. The back-scattered energy
from the area between 0.4 to 2,2 meters from the sensor is picked up by
the transducers and analyzed to find any change in frequency.
The current direction is found by taking the measurements along two
orthogonal axes, x and y. These measurements are compensated for tilt
by use of an electrolytic tilt sensor and referred to magnetic North by means
of an internal Hall-effect compass. A microprocessor computes vector av-
eraged current speed and direction over the last sampling interval. The
sensor output is the Aanderaa standard SR10. A low frequency acoustic
transducer for data transmission is molded into the top of the sensor.

Conductivity Sensor 3919

This sensor measures the conductivity in the water by use of an inductive
cell principle. This provides stable measurements without electrodes that
Conductivity Sensor 3919 Turbidity Sensor 3612 are easily fouled in the field. The conductivity sensor outputs data in both
RS232 and Aanderaa SR10 format. The RS232 outputs the conductiv-
ity in mS/cm. The SR10 provides two output channels. The user may
configure the range on both SR10 outputs, which offers the possibility to
zoom in on the range of interest.

Turbidity Sensor 3612

This sensor measures the turbidity of the water by use of back-scattered
infrared light. This measurement is known to have good correlation to
the amount of suspended matters and can be used to monitor sediments,
algae, or particle pollution. Three light emitting diodes and a photo diode
are pointing to a common center at an angle of 15°. Once every measuring
cycle the light emitting diodes send out light and the reflected light from
Pressure Sensor 3815 Oxygen Optode 3830 particles in the water is pick ed up by the photodiode. The sensor is
shaped as a small cylinder molded in polyurethane material.

Pressure Sensor 3815

The sensor is shaped as a small cylinder molded in Durotong polyurethane. It measures the absolute pressure by means of a
piezoresistive bridge. One measurement is taken for every measurement cycle. This is an analog sensor, and the output is the
Aanderaa standard VR22 signal.

Oxygen Optode 3830

This Oxygen Optode measures dissolved oxygen in fresh and sea water by using the latest technology. The principle of mea-
suremens is bades on the effect of dynamic luminecence quenching (lifetime based) by molecular oxygen.The range is 0-
16mg/l with accuracy ±0.3mg/l or 5 % whichever is greater. The output from the sensor is an SR 10 signal.

DATA SHEET, D 328, OCTOBER 2004 3 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

SPECIFICATIONS FOR RCM9, MK II AANDERAA INSTRUMENTS
Measuring system: A self balancing bridge with sequential measurement of 10 channels and solid state memory. 10-bit binary
word for each channel. The channels are: ( signifies Mk II changes)

Number of Channels: Selectable from 2 to 10 channels Watertight Receptacle:

PIN CONFIGURATION
Ch.1 Reference is a fixed reading to check the RCM’s Receptacle, exterior view; pin = ; bushing =
performance and to identify individual instruments 9Volt input Not connected
3 4
Ch.2 and Ch.3, Current Speed and Direction:
Speed Sensor Type: Doppler Current Sensor 3920 Control Voltage 2 5 PDC-4 Output
Range: 0 to 300cm/s System ground 1 6 Not connected
Resolution: 0.3cm/s
*Accuracy:
Absolute: ±0.15 cm/s External Triggering: A positive 5volt pulse to the electrical
Relative: ±1% of reading terminal, output pin, will trigger one
Statistic precision: 0.5 cm/s (standard deviation) measurement cycle
Direction Sensor : Magnetic compass, Hall effect type Recording Intervals: 1,2,5,10,20,30,60 and 120minutes
Resolution: 0.35° Continuous.(4s x no. of ch. + 2s) and
Accuracy: ±5° for 0-15° tilt and Remote Start only
±7.5° for 15-35° tilt Recording System: Data Storage Unit 2990 or 2990E
Acoustic Frequency: 2 MHz Data storage in EEPROM
Power: 25 Watt in 1 ms pulses Storage Capacity: DSU 2990: 9000 records (7 ch.)
Beam Angle: ±1° (Main Lobe) (2 months at 10 minute interval)
Installation distance: Minimum 0.5m from the bottom DSU 2990E: 36100 records (7 ch.)
(to the DCS head) Minimum 0.75m from the surface (8 months at 10 minute interval)
Ch.4 Temperature: Temperature Sensor 3621 Battery: Alkaline Battery 3614, 9V, 15Ah
Sensor type: Thermistor (Fenwall GB32JM19) (nominal 12.5Ah 220W down to 6V
Resolution: 0.1% of selected range at 4°C) or Lithium Battery 3677, 7.2V
Accuracy: ±0.05°C 30Ah for 1year, respectively 2 years
Response time: 12 seconds (63%) and 4 months operation at one hour
Selectable Ranges: interval, or 92, respectively 220 days
Wide range: –0.64 to 32.87°C at 10 minute interval
Low range: –2.70 to 21.77°C Average Current Consumption (mA):
High range: +9.81 to 36.66°C 0.50 + (50 divided by the recording
Arctic range: –3.01 to 5.92°C interval in minutes)
Ch.5 Conductivity (Optional): Conductivity Sensor 3919 Depth Capability: 1000 meters
Sensor Type: Inductive Cell Dimensions: 513mm High
Range: 0 – 75 mS/cm 128mm OD
Accuracy: ±0.05 mS/cm (3919A) Weight (kg): in air in water
±0.018 mS/cm (3919B) Net (with frame): 22.5 14.5
Resolution: 0.002 mS/cm Gross (with frame): 32.5
Response Time: Setting (90%): <3s Packing: Plywood case: 190 x 250 x 650mm
Ch.6 Pressure (Optional): Pressure Sensor 3815 External Materials: Stainless acid proof steel, Titanium,
Sensor Type: Silicon piezoresistive bridge OSNISIL, Durotong DT 322 polyurethane
Available ranges: 0-700kPa, 0-3500kPa Accessories:
0-7000kPa, 0-20MPa (Included) Mooring Frame 3624 with Sensor
Resolution: 0.1% of range Protecting Ring 966278
Accuracy: ±0.25% of range (Optional) Base Brackets 3627(2) for Frame
Ch.7 Turbidity [Optional):Turbidity Sensor 3612 Additional Protecting Rods 3768
Sensor type: Optical Back-scatter Sensor Vane Plate 3681
Available ranges: 0-20, 0-100, 0-500 NTU DCS Test Unit 3731
Resolution: 0.1 % of full scale PDC-4/RS-232 Converter 3818
Accuracy: 2% of full scale Spares: A set of recommended spares is
Ch.8: Oxygen (Optional): Oxygen Optode 3830 delivered free of charge with each
Sensor Type: Oxygen Optode instrument (o-rings, sealing plugs,
Range: 0 - 500µM tools, cotter pins etc)
Resolution: <1µM Warranty: Two years against faulty materials
Accuracy: <8µM or 5% whichever is greater and workmanship. For subsurface
Response time: Setting (63%): <25 seconds cables contact factory
Depth capacity: 6000 meters * Assumes speed of sound is 1500m/s. Actual speed of
sound can be corrected for using the 5059 program.

DATA SHEET, D 328, OCTOBER 2004 6 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

RCM 9 Mk II Top end plate with sensors and wireing to the Electronic Board

DATA SHEET, D 328, OCTOBER 2004 7 STATE-OF-THE-ART SCIENTIFIC PRODUCTS

DIRECT READING DOPPLER CURRENT METER. RCM 9 AANDERAA INSTRUMENTS
The compact RCM 9 is well suited as a direct reading current meter. The instrument can be lowered with Profiling Cable 3650
using a small winch. The cable may be up to 200m long. On board, Computing Unit 3346 provides the output in engineering units
on a display and as RS232 output for a PC. To stabilize the RCM9 during profiling, the mooring frame is equipped with Vane 3681.
The response time (63%) is 12 seconds for the temperature sensor and one minute for the oxygen sensor. Data can be stored
internally and read after retrieval if an ordinary mooring line is used.

Computing Unit 3346

Data Storage Units DSU 2990 and 2990E
COMPUTING UNIT 3346
SERIAL NO:
with analog output are standard data storage devices for Aanderaa data collecting instruments.
3 4 1 2
2

9
5

8
6

7
OFF 3

5
They are rugged, waterproof and have an LCD that shows the total
number of data word stored. The 2990 version
can store 65 000 10-bit data words and the
Made by

AANDERAA BERGEN
INSTRUMENTS NORWAY

Winch
2990 E version can store 262000 data words.
A built-in quartz clock allows the time of the first
measurement to be recorded in the DSU. Time
Profiling Cable 3650 is also recorded for the first measurement after
up to 200m long
For cables longer than 200m, midnight.
use Cable 3669

Reading of Stored Data

The data can be transferred from the DSU to a
PC using the DSU Reader 2995 and a suitable
communication program. The reader is an RS
232 interface between the PC and the DSU.

Protecting Ring FILING OF DATA

RCM 9 equipped with DSU READER 2995

a Vane for stabilizing

Serial No.

the instrument during

profiling

DATA STORAGE DSU READER PERSONAL COMPUTER PRINTER PROVIDING

UNITS LISTINGS AND GRAPHS

Data Reading Program 5059 is a new software program that may be used to download DSU 2990 data to a Personal Computer. The
program is based on the latest software technology and is designed for use with Windows 95, Windows 98 and Windows NT and 2000.
In addition to enable downloading and exporting of DSU
data, it may also be used for data analysis. The 5059 in-
cludes extensive charting and analysis facilities, and the re-
sulting analysis graphs may be exported to programs such
as Microsoft Word and Excel. The modern user interface, in-
cluding drag & drop facilities, and an extensive built-in Help
system makes the 5059 easy to use.
A sensor, station and instrument library allows you to build

Representative’s Stamp

Engineering_data_graph from Data Reading Program 5059

Latest version is on the Internet

5851 BERGEN, NORWAY TEL. +47 55 109900 FAX. +47 55 109910 E-MAIL: info@aanderaa.no WEB:http://www.aanderaa.no

DATA SHEET, D 328, OCTOBER 2004 8 STATE-OF-THE-ART SCIENTIFIC PRODUCTS