Marine Magnetics SeaQuest2 User manual

SeaQuest2
Operation Manual
Revision 1
Marine Magnetics Corporation
135 SPY Court
Markham, Ontario
L3R 5H6
Canada
Tel: [phone]
fax: [phone]
[e-mail]
www.marinemagnetics.com

Contents
1INTRODUCTION.....................................................................................................................................................1
1.1 SEAQUEST2SYSTEM COMPONENTS:..............................................................................................................................2
1.2 IMPORTANT NOTES ON OPERATION...............................................................................................................................4
1.3 PERFORMANCE CHARACTERISTICS .................................................................................................................................5
1.4UNDERSTANDING THE SYSTEM COMPONENTS .................................................................................................................6
1.4.1 Overhauser total field sensors ......................................................................................................................6
1.4.2 Leak Detector................................................................................................................................................6
1.4.3 Pressure Sensors ...........................................................................................................................................7
1.4.4 Altimeter echo sounder.................................................................................................................................7
1.4.5 IMU (Inertial Measurement Unit) .................................................................................................................8
1.4.6 Electronics Module / Pod ..............................................................................................................................8
1.4.7 Frame............................................................................................................................................................8
1.4.8 Isolation Transceiver .....................................................................................................................................9
1.4.9 AC Power Supply ...........................................................................................................................................9
1.4.10 Tow Cable ...................................................................................................................................................10
1.4.11 Deck Cable ..................................................................................................................................................10
1.4.12 USB Cable....................................................................................................................................................10
1.4.13 RS232 Cable - Optional ...............................................................................................................................10
1.4.14 Adjustable Floats ........................................................................................................................................10
1.4.15 BOB Software..............................................................................................................................................11
2COMMUNICATION VIA THE ISOLATION TRANSCEIVER ........................................................................................12
2.1 TRANSCEIVER SERIAL INTERFACE .................................................................................................................................12
2.2 TRANSCEIVER INTERNAL REAL-TIME CLOCK...................................................................................................................12
2.3 TRANSCEIVER OUTPUT VOLTAGE ................................................................................................................................12
2.4 TRANSCEIVER STATUS LEDS.......................................................................................................................................13
3ASSEMBLING THE SEAQUEST2 PLATFORM ..........................................................................................................14
3.1 SEAQUEST2COMPONENTS........................................................................................................................................14
3.2 TOOLS...................................................................................................................................................................15
3.3 FASTENER AND O-RING SIZES.SPARE PARTS ..................................................................................................................16
3.4 ASSEMBLY INSTRUCTIONS..........................................................................................................................................17
3.4.1 General assembly precautions ....................................................................................................................17
3.4.2 Tail assembly procedure .............................................................................................................................17
3.4.3 Wing assembly procedure...........................................................................................................................18
3.4.4 Float adjustment procedure........................................................................................................................19
4CONNECTING THE EQUIPMENT ...........................................................................................................................20
4.1 MAIN TOW CONNECTOR...........................................................................................................................................22
5DEPLOYMENT......................................................................................................................................................23
5.1 RECOMMENDED DEPLOYMENT SEQUENCE.....................................................................................................................23
5.2 CHECKING CONNECTIVITY AND COMMUNICATION...........................................................................................................23
5.3 SETTING PRESSURE SENSOR ZERO-DEPTH LEVEL ..............................................................................................................23
5.4 HOISTING POINTS ....................................................................................................................................................24
5.5 DEPLOYING THE PLATFORM .......................................................................................................................................25
5.6 BEGIN DATA COLLECTION...........................................................................................................................................25
6SEAQUEST COMMANDS ......................................................................................................................................26
6.1 NORMAL COMMANDS ..............................................................................................................................................26

6.2 ISOLATION TRANSCEIVER COMMANDS .........................................................................................................................29
7SEAQUEST DATA FORMAT...................................................................................................................................30
7.1 SEAQUEST RAW DATA FORMAT .................................................................................................................................30
7.2 CALCULATING THE MAGNETIC GRADIENTS....................................................................................................................31
8INTERFACING TO A SIDE SCAN SONAR ................................................................................................................32
8.1 ANALOG SYSTEMS....................................................................................................................................................32
8.2 DIGITAL SYSTEMS.....................................................................................................................................................32
8.3 COMMUNICATION....................................................................................................................................................33
8.4 BAUD RATE ............................................................................................................................................................33
8.5 ELECTRICAL POWER..................................................................................................................................................33
8.6 MECHANICAL TOW POINT AND ELECTRICAL CONNECTOR PIN-OUT.....................................................................................33
9MAINTENANCE....................................................................................................................................................34
10 TROUBLESHOOTING ........................................................................................................................................35
10.1 TRANSCEIVER TEST PROCEDURE..................................................................................................................................35
10.2 SEAQUEST TEST PROCEDURE .....................................................................................................................................36
10.3 SIDE SCAN INTEGRATION TEST PROCEDURE...................................................................................................................37
10.4 TROUBLESHOOTING..................................................................................................................................................39
10.5 ELECTRICAL SPECIFICATIONS.......................................................................................................................................41
11 HOW TO REACH US..........................................................................................................................................42
11.1 WARRANTY ............................................................................................................................................................42
11.2 INDEMNITY.............................................................................................................................................................42
11.3 DISCLAIMER............................................................................................................................................................42

SeaQuest2 Operating Manual Introduction 1
1
1Introduction
The SeaQuest2 is a 3-axis magnetic gradiometer that is designed to detect ferrous objects and magnetic targets in
marine environments. The SeaQuest frame contains multiple magnetic sensors separated by a fixed and known
distance so that the total gradient of the local magnetic field can be measured directly. The SeaQuest is the first and
only marine gradiometer that allows measurement of all three axial gradients simultaneously. These are: transverse
(across track), longitudinal (along track), and vertical. Measuring all three gradients simultaneously is equivalent to the
direct measurement of the Total Magnetic Gradient, also referred to as the Analytic Signal. The Total Magnetic
Gradient is a superb metric for highlighting near-surface magnetic sources and suppressing the distant background, and
is unaffected by the diurnal magnetic variation.
The SeaQuest2 frame is a significant improvement over the original SeaQuest, featuring a rigid and streamlined frame
that reduces tow drag dramatically, and has fewer parts to assemble before deployment. The rugged SeaQuest2
platform is designed to be towed behind a vessel, and is exceptionally stable. SeaQuest2 comes equipped with a 3-axis
gyro-compensated IMU.
The twin floats enable the SeaQuest2 to remain near the surface when not being towed. The floats are movable, which
allows the user to set the pitch angle of the frame, thus offering control over the desired towing depth.
The built-in altimeter and pressure sensor keep track of the height above seafloor and depth below surface, while the
IMU accurately monitors the attitude angles of the SeaQuest frame. All of this auxiliary data is made available to the
data analyst in both real-time and post-processing.
SeaQuest2 is available in one standard configuration: with 4 sensors, enabling 3 axial pairs with the following fixed
sensor separations:
Gradient Axis
Sensor Separation
Horizontal Transverse
1.5 m
Horizontal Longitudinal
0.81 m
Vertical
0.75 m
Table 1-1 - SeaQuest2 Sensor separations
SeaQuest2 is designed to work with Marine Magnetics BOB data logging and visualization software, which uses the
specified sensor separations when computing the Total Magnetic Gradient (Analytic Signal) in real-time during the
survey.

SeaQuest2 Operating Manual Introduction 2
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1.1 SeaQuest2 system components:
Gradiometer frame that contains 2 wings, a keel and a tail, each equipped with highly-accurate Overhauser
sensors, and a central pod with the driving electronics and auxiliary sensors.
Altimeter single-beam echo sounder, with 1-90m range and 0.1m resolution.
3-axis gyro-compensated IMU, reporting the pitch, roll and yaw angles of the frame.
Pressure (depth) sensor, with 300m range and 0.1m resolution.
Tow cable connector and streamlined nose cone.
High-strength marine tow cable, containing a single twisted wire pair, used for both power delivery and data
transfer.
Deck leader cable that is waterproof, but not designed to be submerged in water.
Isolation transceiver for powering and communicating with the SeaQuest from the deck of a vessel.
Choice of USB or RS232 interface cables that connect the isolation transceiver to a standard PC USB or
RS232 port.
24V DC power supply, universally compatible with 100-240VAC 50/60Hz input.
BOB data acquisition, visualization, and control software for Windows.
External GPS (supplied by the user) capable of GPGGA and GPRMC data output at 1 Hz or higher. 5 Hz
recommended. The GPS can be connected to the isolation transceiver to ensure best possible time
synchronization accuracy between the SeaQuest readings and positions during the survey.
Figure 1-1 - SeaQuest2 System components with a GPS-enabled Isolation Transceiver.
A y-adapter branch of GPS cable connects to the Transceiver for ideal time synchronization with the towfish.

SeaQuest2 Operating Manual Introduction 3
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Figure 1-2 - SeaQuest2 System components with a standard Isolation Transceiver
GPS connects to a separate port on the PC. Data logging software pairs GPS data with magnetometer readings based on
time, and maintains clock synchronization with the towfish.

SeaQuest2 Operating Manual Introduction 4
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1.2 Important Notes on Operation
Similarly to all high performance geophysical instrumentation, there are a few simple rules to ensure optimum
operation of the SeaQuest:
The SeaQuest2 should never be submerged unless all sensor cables are plugged in. Failing to ensure this may
result in leaks and damage to the electronics.
The platform must be towed completely submerged underwater, and ideally below the wave base, to ensure
smooth motion. Do not allow the sensors to break the surface while measuring data.
As with all magnetometers, the platform must be towed far enough behind the survey vessel, so that the
magnetic influence of the vessel is negligible. Generally a minimum distance equal to 3 times the length of the
survey boat is recommended.
The SeaQuest requires a small crane or davit on your vessel for safe and easy deployment and retrieval. Never
allow the frame or the sensor to hit hard surfaces or sides of the vessel, as it may alter the geometry of the
frame and adversely affect the towing characteristics, or damage the sensors.
Always calibrate the zero-level of the depth sensor at the surface before the survey, to ensure accurate readings.
For best results, allow a few minutes for the SeaQuest to adjust to the water temperature before calibrating the
depth zero level.
The float position affects the dive angle and towing depth, and needs to be determined experimentally for each
new survey location and optimal towing depth. Always begin with a conservative position of the floats that
produce only a very minor downward angle under tow, and monitor the depth and altitude carefully as towing
begins, to prevent striking the bottom and causing damage to the platform and sensors.
Never hoist the SeaQuest by its floats. Make sure the hoisting line does not wrap around or push against the
floats. The float assembly is not designed to take the full weight of the SeaQuest frame when out of the water.
Applying excessive load to either wings, floats, tail or sensor pods can lead to damage or deformation, which
may adversely affect the towing characteristics, or cause damage to the sensors.
Never allow the frame or sensor pods to swing out of control while hoisted, or hit any hard surfaces. This may
lead to permanent damage to the sensors or frame.
Note that the altimeter is located in the nose bulkhead, approximately 0.76m higher than the lowest point of the
vertical wing. Be sure to account for this ‘draft’ when interpreting the altitude readings, to avoid striking the
bottom with the keel sensor.
Figure 1-3 - Altimeter echo-sounder location relative to lowest point on the frame
Refer to the following sections for details on each of the auxiliary sensors and float positioning.

SeaQuest2 Operating Manual Introduction 5
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1.3 Performance Characteristics
The SeaQuest’s most important characteristic is the superb absolute accuracy of its Overhauser sensors. A magnetic
gradiometer must be able to reliably report an accurate zero-gradient to be useful. The only way this can be achieved is
by having extremely accurate repeatability between sensors. The SeaQuest’s Overhauser sensors are repeatable to
better than 0.01nT, and they show zero detectable heading error.
Another important characteristic is platform stability. In order for the magnetic field readings to have meaning, a
gradiometer must provide accurate spatial position data for its sensors. The SeaQuest incorporates an acoustic
altimeter and pressure sensor to report its vertical position in the water column, and an accurate 3-axis gyro-
compensated IMU to report pitch, roll and yaw angles of the frame. Most importantly, the platform is extremely hydro-
dynamically stable, which minimizes the need for dynamic compensation for motion effects as long as the platform is
towed at a depth unaffected by surface waves.
The SeaQuest provides a base noise spectral density of 0.01nT-RMS/rt-Hz per sensor. This translates to roughly
0.009nT/m noise in horizontal gradient, and 0.028nT/m noise in vertical gradient.
Relating noise levels to actual detectable changes requires us to define a threshold signal-to-noise ratio (SNR) that we
can use to identify anomalies. Using a practical SNR of 10:1, the SeaQuest’s practical magnetic gradient detection levels
are 0.1nT/m horizontal and about 0.25nT/m vertical. This is an order of magnitude finer than the deviation one would
see from gradiometers based on other technologies simply by rotating them in place, and measuring their heading
error.
Although the SeaQuest features a superb sensitivity and extremely low intrinsic noise, it is important to take into
account the local background noise present at and unique to each survey site, which can be significant, depending on
the type of location and presence or proximity to man-made infrastructure.

SeaQuest2 Operating Manual Introduction 6
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1.4 Understanding the System Components
1.4.1 Overhauser total field sensors
Marine Magnetics supplies a separate document titled the SeaSPY Technical Application Guide containing an in-depth
description of how the Overhauser sensors work as well as general guidelines for estimating the size of magnetic
anomalies produced by a given amounts of ferrous iron. Marine Magnetics provides this document to anyone free of
charge, so please contact us if you do not already have a copy.
All SeaQuest gradiometers are supplied with omnidirectional sensors that are completely isotropic with respect to
magnetic field direction. The only restriction that must be observed is that SeaQuest2 must not be oriented vertically
with the nose facing upwards. This is a restriction with respect to the direction of gravity, not magnetic field.
The Overhauser sensor measures magnetic flux density, the unit for which is the Tesla (T). Magnetic flux density on the
surface of the Earth typically varies between about 18T to 70T, depending on location. The flux density at any fixed
location on the Earth’s surface also varies with time of day, due to diurnal effects, which include influence from the Sun
(mainly the interaction of the Sun’s radiation with Earth’s atmosphere, which is subject to regular and random
changes), and movement of the Earth’s molten interior.
One often speaks of a magnetometer as measuring magnetic field instead of flux density, since the two values are
directly related given an environment of constant magnetic permeability (such as air or water). Some materials will
distort the surrounding magnetic flux density by ‘amplifying’ or adding to the ambient magnetic field. Such objects are
known as paramagnetic. Some materials (such as iron, nickel, cobalt and alloys containing these materials) exhibit this
effect very strongly, and are known as ferromagnetic. Objects made from these materials are very easily detectable by
a magnetometer. Most building materials, especially those used to build modern boats and ships, contain iron alloys
and are therefore magnetic. Some stainless steels (austenitic alloys such as 316) are only weakly ferromagnetic, but will
become more strongly magnetic if their microstructure is disturbed by annealing, welding, machining or severe
stressing. In addition to ferrous construction materials, there is a number of naturally-occurring minerals (e.g. iron
oxides) that can be strongly magnetic. Such minerals are commonly found in igneous and volcanic rocks, as well as
pottery, and any accumulations of gravel and boulders derived from igneous rocks. Surveying in environments
dominated by igneous or volcanic bedrock can present challenges to the data analyst, and requires especially careful
control of survey altitude.
Carbonate-based rocks, on the other hand, do not contain any magnetic minerals, and areas dominated by limestone
or sedimentary bedrock do not usually create a strongly-variable magnetic background, but tend to be affected by
diurnal variation to a greater degree. For this reason the use of a base station magnetometer is especially
recommended in non-magnetic bedrock environments.
When an object of high magnetic permeability distorts the flux density around it, it creates a magnetic gradient that is
proportional to the magnitude of its permeability. If the magnetic gradient through the volume of the magnetometer
sensor is too great, the sensor will not operate correctly. For this reason, massive magnetic objects must be kept away
from the sensor. Do not expect the magnetometer to produce good results on the deck of a ship, or inside a building,
or next to a rocky outcrop containing igneous or volcanic rocks, any more than you would expect a high-powered
telescope to see distant stars in the middle of the day or through a dirty window.
For more information on magnetic fields and operation of the Overhauser magnetometers, please refer to the SeaSPY
Technical Application Guide. This document can be obtained from Marine Magnetics.
1.4.2 Leak Detector
Each SeaQuest is equipped with a leak sensor that triggers a warning in BOB when water is present inside the
electronics pod. The message “WARNING! WATER DETECTED IN CENTER POD” will also appear in the command
window every 10 seconds. Even a small drop of water will activate the leak sensor. In the event of a leak warning, the
SeaQuest should be retrieved immediately, as it is very likely that a leak has developed in the electronics housing.
Water inside the electronics pod may damage the electronics module and Overhauser sensors.

SeaQuest2 Operating Manual Introduction 7
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1.4.3 Pressure Sensors
The standard SeaQuest pressure sensor is a Wheatstone bridge on a silicon diaphragm. The maximum pressure that
this sensor can withstand before potentially suffering damage depends on the pressure rating of the housings.
Exceeding the rated depth can cause a change in the calibration tuning of the sensor, and its accuracy may suffer as a
result. The pressure sensor will not suffer serious mechanical damage (i.e. will not rupture and cause a leak) until
exposed to twice its rated operating pressure.
Note that the SeaQuest2 housing is available with a single depth rating of 300m. Take care not to exceed this depth to
prevent damage to the housing.
SeaQuest can interface seamlessly to a variety of other pressure sensors, suited for shallow or deep work. In general, a
larger pressure sensor range will result in lower precision in the pressure reading.
Range (psi)
Range (m)
Precision
Installation
150
100
0.1 m
optional
500
345
0.1 m
standard
table 1-1: Pressure sensor options
The pressure sensor is an analog device that may drift with temperature and with time. For proper operation, the
pressure sensor zero-level should be reset before every survey, after allowing the SeaQuest to adjust to the
temperature of the water. For optimal results the platform should be submerged for several minutes to allow the
temperature of the pressure sensor to reach the ambient water temperature. Following that, the pressure sensor zero-
level can be calibrated at the surface or above water. The zero-level calibration can be done through BOB, or by
sending a p(lower-case p) command via a serial terminal.
The P(upper-case P) command will display the current pressure range calibration settings, and will offer the option to
set the full-scale pressure calibration. The full-scale calibration is factory-set, and does not need to be altered by the
operator unless below-nominal full-scale accuracy is suspected. Unless specifically instructed to do so by Marine
Magnetics technical support, do not attempt to alter the pressure range calibration as it requires full control of the
water pressure and may adversely affect the accuracy of the sensor readings if done incorrectly.
Refer to Section 6 (page 26) for details on the command interface.
1.4.4 Altimeter echo sounder
A 200kHz narrow-beam echo sounder is located on the bottom of the nose bulkhead. This device senses the distance
from the face of the transducer to the sea floor by emitting 10 sound pulses per second, and providing these altitude
readings to the SeaQuest electronics. Note that the bottom of the SeaQuest vertical wing will be closer to the sea floor
than the transducer, so be careful to ensure that the bottom wing does strike the sea floor or any obstructions that
may cause physical damage to the frame of sensors.
The SeaQuest altimeter has a range of 0.5m to 90m, and a resolution of 0.01m. To see the current altitude of the
platform, use the dcommand. Altitude is displayed in meters as ‘A005.00m’. In addition, an altitude reading is included
in every magnetic field reading to allow real-time monitoring. Note that the altitude data field does not appear if the
altimeter is not installed in the platform.
The altimeter does not work when out of the water, and will display a value of 599m, representing an out-of-range
condition. This indicates that the altimeter cannot ‘find’ a surface underneath the platform, but otherwise working
properly. If the altimeter were to stop working, the altitude reading would disappear from the data stream completely.

SeaQuest2 Operating Manual Introduction 8
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1.4.5 IMU (Inertial Measurement Unit)
The SeaQuest is equipped with a 3-axis IMU containing a 3-axis gyro that provides very accurate measurements of the
pitch, roll and yaw attitude angles of the SeaQuest frame. The yaw angle (+/- 180) is converted to heading (0-360)
automatically by the SeaQuest2 electronics.
Although the platform orientation does not impact the operation of the sensors, or the value of the Total Magnetic
Gradient, it is important to keep in mind that it does impact individual gradient measurements if one were to study and
interpret those individually. (e.g. with a pitch angle of 45 degrees, the vertical gradient is no longer vertical, etc.)
If you observe a regular rhythmic oscillation in the vertical gradient when under tow, it could be that the SeaQuest is
not deep enough below the surface waves, causing it to move unevenly through the water.
IMU readings are added at the end of each magnetic field data string as p00.0, r00.0, h00.0, and can be monitored in
real time using the Attitude Indicator tool in BOB, or in graph form on the BOB Profile Plot. Please refer to the BOB User
Manual for details.
The pitch, roll and heading (yaw) angles use the following sign convention:
pitch
Positive direction with nose downward: Range: +/-179.9
roll
Positive direction with starboard side down. Range: +/-179.9
heading
Positive counter-clockwise from magnetic north. Range: 0 - 359
Table 1-2 - IMU attitude angle sign convention
The IMU is factory calibrated prior to shipment and does not require user calibration. However, a small deviation of the
heading angle from the true magnetic north direction may be observed in some situations.
To see a high-frequency IMU data feed, use the mcommand in the terminal. Refer to Section 6 (page 26) for details
on the command interface.
1.4.6 Electronics Module / Pod
The SeaQuest electronics module is the core of the SeaQuest system, located in the center of the frame. It controls all
of the sensors in the platform, monitors their performance, and reports their data to the host acquisition device
digitally over the tow cable connection. Interface to the electronics module is through a single two-wire connection,
which has DC Power and telemetry multiplexed into it.
All SeaQuest electronics modules are completely interchangeable. The only difference between them is a 16-bit serial
number that is stored in non-volatile RAM within the unit.
The SeaQuest2 should never be submerged unless all sensor cables are plugged in.
The electronics pod is not fully pressure-sealed unless all sensor cables are plugged into it. The protective dust caps for
connectors and tubes do not offer protection against water pressure.
1.4.7 Frame
The SeaQuest2 frame is a rigid streamlined structure consisting of two wings, one keel, and one tail boom, all
connected to a central core. The wings and keel feature the same streamlined design of rigid hard-anodized aluminum
that provides strength and rigidity. Sacrificial anodes are attached to aluminum parts to reduce corrosion. The keel and
wings are identical, except for their weight –the keel is made to be heavier. The keel can be identified by a distinct
color of surface anodizing, as well as additional drainage hole near the sensor pod.
Four Overhauser sensors are mounted in pods at the tips of the horizontal and vertical wings, as well the tail boom.
The central core contains the electronics module, which also includes the IMU, pressure sensor and altimeter
electronics.

SeaQuest2 Operating Manual Introduction 9
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The nose contains a brass tow connector that is designed to bear the entire load of the tow system in addition to
providing a two-conductor electrical connection. Note that the shell of the connector is AC-coupled to the system
ground, and is connected electrically to the water, providing a sea ground.
The pressure housings for Overhauser sensors and the electronics pod consist of a filament-wound fiberglass cylinder
coated with polyurethane for abrasion and shock resistance.
SeaQuest2 is available in one single depth rating: 300m.
Only completely non-magnetic materials are used in the entire SeaQuest assembly, including all fasteners and
components. This is to ensure a zero heading shift and to eliminate any sources of magnetic interference and
guarantee the excellent signal quality and low noise characteristics of the SeaQuest.
Should any of the fasteners require replacement, be sure to request the appropriate original fasteners from Marine
Magnetics, which are made from specific materials such as naval brass and titanium. Do not attempt to replace the
fasteners with anything else.
For a list of O-ring sizes in the housing seals, refer to Section 3.3 (page 16).
1.4.8 Isolation Transceiver
The SeaQuest2 Isolation Transceiver consists of power-conditioning electronics that supplies clean constant power to
the SeaQuest, as well as a microprocessor to bridge the communication between the SeaQuest’s FSK protocol and the
PC’s RS232 interface. Power and RS232 are both fully isolated from the supply ground, providing extremely high
immunity to noisy power supplies at all frequencies. The wide input range of +9VDC to +28VDC allows for operation
with both 12VDC and 24VDC lead acid batteries. Internal regulators produce a constant +48VDC to power the
SeaQuest. The power and communication to the SeaQuest are multiplexed together for use with a two-conductor
cable. This hardware is sealed in a rugged housing that is splash proof, but not waterproof.
The transceiver also supports USB for use with computers that do not have a standard serial port. For more
information on how to connect the transceiver, refer to Section 2(page 12).
An Isolation Transceiver is able to communicate with a SeaQuest platform across up to 10,000m (32,808ft) of the
standard SeaQuest twisted-pair tow cable.
A new generation Isolation Transceiver is available as of 2022, which includes a GPS input connector. This allows the
boat-mounted GPS to be connected directly to the Transceiver through a Y-adapter, in addition to being connected to
the PC. This allows the Transceiver to use the NMEA UTC time and date for perfect time synchronization between the
GPS positions and magnetometer readings.
1.4.9 AC Power Supply
In most cases, electrical power to the SeaQuest towfish will be supplied by the Isolation Transceiver, which produces a
clean, constant +48VDC to power the unit. The input range for the Isolation Transceiver is +9 to +28VDC.
If the Isolation Transceiver isn’t used in the deployment, power conditioning should be as follows:
SeaQuest requires DC power with a range of +30V to +50V
For long tow cables (longer than 300m) it is recommended to keep the supply voltage above +35V
It is always recommended to keep the supply voltage as close to the upper limit as possible in order to compensate
for the voltage drop in the tow cable
The maximum power consumed by the towfish is approximately 20W when acquiring data (including the
altimeter), and is typically around 8W when in standby. The Isolation Transceiver consumes an additional 2W.
The standard SeaQuest AC power powers the Isolation Transceiver with 24VDC output, and can accept any input AC
power from 100 to 240VAC, at 50/60Hz offering worldwide compatibility.

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Note that the AC power supply uses a 3-prong North American style plug. It is extremely important that the third
(middle) prong from this plug is connected to a proper ground, boat hull or sea ground. Without a good ground
connection, you may experience communication problems, or even a degradation of magnetometer performance.
Battery Clip Cable (Optional) is an alternative method for powering the Isolation Transceiver, and can be connected to
any 12V or 24V battery. 24V is recommended for gradiometers.
Note that the voltage of a typical 12VDC lead-acid battery will vary from approximately 14VDC when fully charged to
approximately 9VDC when nearly discharged. A 24VDC lead-acid battery set will provide a range of 18 to 28VDC going
to the SeaQuest system over the full charge cycle of the battery set.
The SeaQuest Isolation Transceiver contains protection against polarity reversal. Therefore, connecting the black clip to
the positive terminal, and the red clip to the negative terminal will cause no damage. However, no protection exists
against over-voltage. Use caution not to connect the battery clips to any voltage higher than 28V.
1.4.10 Tow Cable
The standard SeaQuest tow cable (yellow in color) is a shielded twisted pair (two conductors plus shield) with a high
strength, lightweight braided Vectran strength member. The tow cable can withstand loads of up to 1000lb without any
damage, and loads of up to 6000lb without breaking. It is sheathed in a tough polyurethane jacket and is fully water
blocked. This means that if the jacket is cut or damaged, water migration through the tow cable will be greatly slowed,
but not completely stopped depending on the external pressure. A damaged cable jacket should be repaired as soon as
possible.
The two conductors in the tow cable carry both the DC power and the telemetry signals, for powering and
communicating with the SeaQuest. The red conductor carries the positive voltage and telemetry, and the black
conductor carries the negative voltage and common ground. The outer braid is only used to shield the inner two wires
from external noise, not to carry electric current. It is connected to the cable’s negative conductor at the source
(topside) end of the cable only.
1.4.11 Deck Cable
The deck leader cable is designed to connect the main tow cable spool, which is usually left on the deck of the
deployment vessel near the stern, to the Isolation Transceiver, which is normally kept in a controlled interior
environment. The deck cable’s jacket is very tough polyurethane that is designed to withstand rain, extreme abrasion
and crushing, but is not designed to withstand towing force.
1.4.12 USB Cable
The USB cable connects the Isolation Transceiver to your PC. It is a gray cable with one USB connector that plugs into
the PC, and one female 8-pin circular connector that connects to the Isolation Transceiver.
This cable is useful for laptops or computers that do not have a standard serial port. The Isolation Transceiver contains
a built-in RS232-USB adapter, which acts as a virtual COM port on the computer. The USB driver for this adapter is
supplied with BOB software. Please note that this virtual COM port is available only when the transceiver is powered.
1.4.13 RS232 Cable - Optional
The RS232 cable is an optional replacement for the USB cable. It is a gray cable with one female 9-pin DSUB connector
that plugs into the serial port of your PC, and one female 8-pin circular connector that connects to the Isolation
Transceiver. An RS232-USB adapter (commercially available) can be used for computers lacking a serial port. Unlike the
USB cable, using an external RS232-USB adapter makes the virtual COM port available even when the transceiver is not
powered.
1.4.14 Adjustable Floats
SeaQuest2 has two floats above the electronics pod, which can be adjusted by sliding them forward of aft.

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This allows the user to change the center of buoyancy of the entire frame, and change the pitch angle of the wings.
Moving the floats forward will reduce the pitch angle, and allow the SeaQuest to remain at or near the surface when
under tow. Moving the floats aft will increase the pitch angle, and force the SeaQuest2 to dive when under tow.
The float position needs to be determined experimentally for each new survey location and desired towing depth, as it
depends on the towing velocity and the pitch angle of the frame, and the optimal towing depth for each specific
survey.
Always begin with a conservative position of the floats that allows the SeaQuest2 to remain close to the surface, which
exposes approximately 7” of the forward end of the float. Try towing and observe the behavior.
Refer to Section 3.4.4 (page 19) for details on float adjustment.
Figure 1-4 - Default position of the floats
1.4.15 BOB Software
Marine Magnetics BOB is a Windows application that interfaces with your magnetometer, to allow full control
over the towfish, data collection, survey planning and data visualization. For detailed information on using this
program refer to the BOB Operation Manual. Visit: https://bob.marinemagnetics.com/

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2Communication via the Isolation Transceiver
By default, all communication with the SeaQuest is via the Isolation Transceiver, which inserts an intelligent layer
between data logging software and the towfish. The transceiver assumes complete control over the tow cable
communication link, and time synchronization with the GPS, as well as supplies optimal power to the towfish for a wide
variety of cable lengths and specifications.
2.1 Transceiver Serial interface
The connection between the data logging computer and the Transceiver is via RS232 interface, using:
115200 baud
8 data bits
No parity
1 stop bit
Communication is full-duplex. Any commands that are sent to the SeaQuest while it is transmitting will not disrupt the
transmission.
When using the supplied USB cable, the transceiver’s integrated RS232-USB converter is used, which emulates a virtual
COM port with the same settings.
When you send a command to transceiver, you may get a response even if there is no SeaQuest connected. For
example, you can query and set the transceiver’s internal time and date without the SeaQuest connected. As soon as
you connect the SeaQuest, the transceiver will recognize the SeaQuest, and set its time as necessary.
Refer to Section 6 (page 26) for details on the command interface.
2.2 Transceiver Internal Real-Time Clock
The Isolation Transceiver contains a real-time clock that it used to synchronize the clock inside the SeaQuest during the
survey. The transceiver real-time clock continues running when power is disconnected. The clock is powered by an
internal lithium battery that automatically recharges when power is applied to the transceiver. The clock will keep time
accurate to 0.65 seconds per day in ambient temperatures of –40 to +85˚C, or accurate to 0.15 seconds per day in
ambient temperatures of 0 to +40˚C.
Note that after an extended storage period between surveys (several weeks), the internal real-time clock battery may
discharge and the clock will reset to zero. For this reason, it is recommended to “charge” the transceiver for at least 6
hours prior to the survey following an extended period of storage. This will ensure that the real-time clock battery will
be sufficiently charged to ignore any power cycles that may occur during the survey.
2.3 Transceiver Output Voltage
Standard isolation transceiver units are built to output +48VDC to the SeaQuest tow cable, using input voltages of +9 to
+28VDC. Power and RS232 are both fully isolated from the supply ground, providing extremely high immunity to noisy
power supplies at all frequencies.
Note that all isolation transceiver units use a 1.0A resettable input fuse. If your input voltage is too low, the transceiver
will have to draw more current to supply the same power to the SeaQuest tow system. For this reason a 24V input
source is recommended for most situations.
The resettable fuse has a variable trip delay based on the amount of over-current. For example, if the transceiver is
drawing 1200mA, you may find that the SeaQuest system will work well for a short while, and then trip the fuse for no
apparent reason. If your transceiver seems to ‘go dead,’ it is possible that you have simply tripped the fuse due to input
voltage being too low. Simply power down the system, wait a few seconds, and then turn it on again.
You can monitor the transceiver input and output voltages and currents at any time using the dcommand. Refer to
Section 6 (page 26) for details on the command interface.

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2.4 Transceiver Status LEDs
The Isolation Transceiver has two status LEDs, one for power and one for communication. The LED modes indicate the
following states:
Power LED
Orange
SeaQuest not
connected/maidetected.
Green
SeaQuest is detected and
powered.
Red
Fault condition. Or Transceiver
disabled power to towfish.
Communications LED
Blue (flashing)
Data is being transmitted.
Table 2-1 - LED indicators on the Isolation Transceiver

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3Assembling the SeaQuest2 Platform
3.1 SeaQuest2 Components
Figure 3-1 - SeaQuest2 assembly showing individual components
Core with the electronics pod and floats
Tail with sensor pod and stabilizer fins.
Note the correct orientation, for optimal stability when
under tow

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Two wings with sensor pods
Keel with sensor pod
Note the distinct color of anodizing, and an additional
drainage hole on the keel
Hardware required for assembly:
Wing anchor bushing –
Long
x6
Wing anchor bushing –
Short
x6
Wing anchor bolt
(socket head)
x6
Tail tube screw
(Phillips)
x6
All hardware must be completely non-magnetic to ensure correct operation of the SeaQuest. Contact Marine
Magnetics for spare parts whenever necessary.
3.2 Tools
3/16” hex Allen wrench (for tail section clamp)
Phillips screwdriver (for tail section tube flange)
5/16” hex Allen wrench (for wings and float assembly)
11/16” socket wrench (for wings)

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3.3 Fastener and O-ring sizes. Spare parts
Tail connection detail
O-ring and screw sizes
Tail sensor cable connector
O-ring size
Wing fastener detail
O-ring and screw sizes
Wing sensor cable connector
O-ring size

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3.4 Assembly Instructions
3.4.1 General assembly precautions
Always ensure you have a clean surface to work on, free of debris and sand, to prevent contaminating the seals on the
tail tube flange, and inside the sensor cable connectors.
Sand is highly-abrasive, and often magnetic. Getting sand into any part of the frame could compromise the water seals,
and introduce a source of magnetic noise.
If any debris is present on the seals or seal surfaces, wipe all the mating surfaces with a lint-free cloth, and apply extra
silicone lubricant. Replace the O-ring seals if you see any signs of damage on the rubber.
Never allow water to get into the sensor cable connectors. If necessary, blow the water out with compressed air, or
wait for it to dry. Presence of water inside the coaxial sensor connector may compromise the sensor signals and result
in poor sensor performance, or damage to the electronics.
3.4.2 Tail assembly procedure
Place the core module upside-down on a clean flat surface free of abrasives
Fit the tail section through the clamp at the rear of the core
Fasten the electrical connectors –hand-tight only! Observe the color coding.
Slide the tail tube over the lubricated O-ring seals
Carefully align the screw openings with the corresponding threaded holes on the core flange
Carefully thread the flange screws in. To prevent cross-threading, always start turning the screw counter-clockwise
first, until you feel the screw “click” into the start of the thread, and then proceed to turn it clock-wise.
Do not overtighten flange screws to prevent damage to the core flange threads. The water seal is ensured by the
O-rings, not the screws!
Figure 3-2 - Tail attachment detailed view