SG Brown Meridian User guide

A Division of VT TSS (UK) Limited
The information in this Manual is subject to
change without notice and does not represent
a commitment on the part of SG Brown
Abcdef
VT TSS (SG Brown Division) Ltd
1 Garnett Close
Greycaine Industrial Estate
Watford
Hertfordshire WD24 7JZ UK
Telephone [phone]
Facsimile [phone]
Meridian Gyrocompass
System Manual
Document P/N 060070
Issue 3.7
© SG Brown March 2004

Contents
DPN 060070 Issue 3.7 © SGBrown Page 1 of 6
CAUTIONARY NOTICES
Your attention is drawn to the following cautionary notices that apply throughout this Manual.
WARNING
The Meridian Gyrocompass weighs 15.5kg. To avoid personal injury, take proper pre-
cautions if you lift or move the equipment.
CAUTION
The Meridian Gyrocompass includes precision components and bearings. To avoid
causing damage to any part of the System, handle all items with care.
Retain the original transit cases so that you can use them to transport the system when
necessary. You will void the warranty if you use improper packing during transporta-
tion.
CAUTION
Severe damage to the Meridian Gyrocompass can occur if you move the gyrocompass
while the rotor is still spinning without the servo system in operation.
Note that the gyro rotor continues to spin for approximately five minutes after you
power-off the system.
To avoid potential damage to the Meridian Gyrocompass, always allow a period of five
minutes after power-off for the gyro rotor to come to rest before you attempt to move
the gyrocompass.
CAUTION
During operation, the gyrocompass must remain level to within ±45°. If it experiences
tilt greater than 45° in any direction, it will ‘topple’. Safety routines in the gyro software
will then power-off the gyro rotor and show alarm conditions on the RCU. To restore
normal operation, establish a level operating attitude and then power-on the gyrocom-
pass normally.
Never apply a tilt of more than 45° with the gyro rotor spinning or during the gyrocom-
pass initialisation procedure. Note that the gyro rotor continues to spin for approxi-
mately five minutes after you power-off the System.
CAUTION
If you install the gyrocompass in an enclosed space, make certain there is sufficient
ventilation and circulation of free air to allow effective cooling.
CAUTION
Do not make any connections to the gyrocompass with power on the supply cable.

Meridian Gyrocompass
Page 2 of 6 ©SGBrown Issue 3.7 DPN 060070
CAUTION
You will void the warranty if you make any modifications to this equipment without
prior permission from SG Brown.
DO NOT modify this equipment in any way without obtaining permission from SG
Brown.
CAUTION
You will void the warranty if you operate the gyrocompass outside the environmental
conditions detailed in Chapter 4 and in BS EN 60945.

Contents
DPN 060070 Issue 3.7 © SGBrown Page 3 of 6
CONTENTS
1 INTRODUCTION 1–1
1.1 System Description 1–3
1.1.1 Gyrocompass 1–3
1.1.2 Remote Control Unit 1–4
1.1.3 Auxiliary Inputs 1–4
1.1.4 Heading Outputs 1–5
1.2 Principle of Operation 1–5
2 INSTALLATION 2–1
2.1 Unpacking and Inspection 2–2
2.2 Physical and Electrical Installation 2–3
2.2.1 Selecting a location 2–3
2.2.2 Gyrocompass installation 2–4
2.2.3 External Remote Control Unit 2–9
2.2.4 Set the Gyrocompass DIP Switches 2–10
2.3 Alignment 2–12
2.4 Final Gyrocompass Installation Tests 2–12
2.5 Installation Drawings 2–13
3 OPERATING INSTRUCTIONS 3–1
3.1 Control Features 3–2
3.2 Initial Power-on 3–3
3.3 Operating Procedure 3–4
3.3.1 Latitude correction 3–4
3.3.2 Speed correction 3–4
3.3.3 DG operating mode 3–5
3.4 Error Modes 3–5
3.4.1 Loss of GPS 3–5
3.4.2 Loss of speed log 3–6
3.4.3 Gyrocompass system warnings and failures 3–6
3.5 Operating Considerations 3–8
3.5.1 General Operating Considerations 3–8
3.5.2 Corrections for Speed and Latitude 3–8
3.5.3 Operating at Extremes of Latitudes 3–8
3.5.4 Operating Considerations for High Speed Craft 3–9
4 TECHNICAL DATA 4–1
4.1 Specifications 4–1
4.1.1 Power Requirements 4–1
4.1.2 Performance (definitions as in ISO 8728) 4–1
4.1.3 Compensation 4–1
4.1.4 Environment 4–1
4.1.5 Signal Inputs 4–2
4.1.6 Signal outputs 4–2
4.1.7 Dimensions and Weight 4–2
4.1.8 Listener load requirement 4–3
4.1.9 Talker drive capability 4–3

Meridian Gyrocompass
Page 4 of 6 ©SGBrown Issue 3.7 DPN 060070
4.1.10 Standards 4–3
4.2 Data Formats 4–4
4.2.1 IEC 61162 Serial Data Formats – General information 4–5
4.2.2 Inputs 4–6
4.2.2.1 IEC 61162 input signals 4–6
4.2.2.2 Pulsed input 4–10
4.2.3 Outputs 4–11
4.2.3.1 IEC 61162 output signals 4–11
4.2.4 IEC 61162 sentence with Checksum 4–15
4.2.5 Other Output Formats 4–15
4.2.5.1 Course Recorder Output 4–15
4.2.5.2 Synchro Output 4–16
4.2.5.3 Resolver Output 4–16
4.2.5.4 Stepper S-Code 4–16
4.2.5.5 Rate of Turn 4–16
5 MAINTENANCE 5–1
5.1 Built-in Test Equipment 5–2
5.1.1 Azimuth Drift Adjustment 5–3
5.1.2 Azimuth Bias Adjustment 5–3
5.2 Test Connector 5–4
5.3 Diagnostic Output Sentence 5–6
A OPERATING THEORY A–1
A.1 North-seeking Gyroscope A–2
A.2 Gyrocompass Corrections A–5
A.2.1 Latitude Correction A–5
A.2.2 Gyro Damping A–5
A.2.3 Speed Error A–6
A.3 Summary A–7
B CERTIFICATION A–1

Contents
DPN 060070 Issue 3.7 © SGBrown Page 5 of 6
TABLE OF AMENDMENTS
Old Issue New Issue Date Details
-2.0 11 May 2000 New release.
2.0 2.0A 12 Dec 2000 Corrected identification of Azimuth Bias potentiometer and
other details. Include DIP switch default settings.
2.0A 2.0B 1 Mar 2001 Modify power connection details.
2.0B 2.0C 23 Apr 2001 Add notification to avoid product modifications.
2.0C 3.0 Aug 2002 Substantial amendments to reflect product enhancements
3.0 3.1 Sept 2002 completion of enhancement features including compliance with
IEC 61162
3.1 3.2 Jan 2003 Minor amendments and description of Diagnostic Output Sen-
tence.
3.2 3.3 Feb 2003 Modification to specifications and addition of Appendix B to
demonstrate Certificate of Type Approval.
3.3 3.4 Mar 2003 Minor amendments to a display warning and a note referring to
confirming software release.
3.4 3.5 July 2003 Note added regarding modification kit available for alternative
orientations when attempting correct speed compensation.
3.5 3.6 August 2003 Minor amendments to specifications throughout
3.6 3.7 March 2004 Amendments to alarm warning / failure designation

Meridian Gyrocompass
Page 6 of 6 ©SGBrown Issue 3.7 DPN 060070

1 – Introduction
DPN 060070 Issue 3.7 © SG Brown Chapter 1 Page 1 of 6
1 INTRODUCTION
The Meridian Gyrocompass is a master heading reference instrument that applies the charac-
teristics of a dynamically tuned gyroscope and the effects of gravity and earth rotation to pro-
vide a true north reference.
The Meridian Gyrocompass specification makes the System ideal for installation and opera-
tion on board vessels of almost any size and in a wide range of applications.
Among the standard features of the Meridian Gyrocompass are:
❐A short settling time
❐Operation from a 24V DC electrical supply
This Manual is an important part of the Meridian Gyrocompass. It describes the System and
contains full installation and operating instructions. You should retain the Manual with the
System for use by personnel who will install and operate it.
Installation and operation of the Meridian Gyrocompass are not complex tasks. However, you
should spend time to familiarise yourself with the contents of this Manual before you start to
install or use the System. Time spent in identifying the task sequence now will ensure your
System is operational in the minimum of time.
WARNINGS
Where appropriate, this Manual includes important safety information highlighted as
WARNING and CAUTION instructions. You must obey these instructions:
WARNING instructions alert you to a potential risk of death or injury to users of the
System.
CAUTION instructions alert you to the potential risk of damage to the System.
For your convenience, the Table of Contents section includes copies of all the
WARNING and CAUTION instructions included in this Manual.
Throughout this Manual all measurements conform to the SI standard of units unless other-
wise indicated.
For your convenience, this Manual includes several sections, each of which describes specific
features of the Meridian Gyrocompass:
You should read sections 1 and 2 before you attempt to install the System:
Section 1 contains introductory notes and describes those items supplied as standard.
Section 2 describes how to select a suitable location for the gyrocompass. This section
includes full instructions to install the System and connect it to external equipment.

Meridian Gyrocompass
Chapter 1 Page 2 of 6 © SG Brown Issue 3.7 DPN060070
You should read sections 3 and 4 before you use the System:
Section 3 describes how to operate the Meridian Gyrocompass.
Section 4 includes the System specifications and descriptions of the data formats.
You should read sections 5 if you suspect a fault on the System:
Section 5 describes how to use the internal 60-way test connector and explains how to con-
duct simple adjustments with the gyrocompass housing removed.
This Manual also contains the following appendices:
Appendix A explains how a gyroscope can be made north seeking for use in a gyrocompass.
CAUTION
You will void the warranty if you make any modifications to this equipment without
prior permission from SG Brown.
DO NOT modify this equipment in any way without obtaining permission from SG
Brown.

1 – Introduction
DPN 060070 Issue 3.7 © SG Brown Chapter 1 Page 3 of 6
1.1 SYSTEM DESCRIPTION
The Meridian Gyrocompass comprises two sub-assemblies:
❐The gyrocompass housing
❐The Remote Control Unit (RCU)
Figure 1–1 shows the combined gyrocompass housing with the RCU included as an integral
unit.
The Meridian Gyrocompass applies dynamic tuning to settle automatically to the meridian.
Due to the physical principles of a north-seeking gyrocompass, achievable accuracy depends
on the operating latitude and the vessel dynamics. To optimise its performance, the Meridian
Gyrocompass uses information supplied by external equipment, for example a GPS receiver
and a speed log, to apply latitude and speed corrections.
Refer to Appendix A for a simplified explanation of the gyrocompass theory of operation.
1.1.1 Gyrocompass
Figure 1–1: Gyrocompass housing with
integral RCU
Figure 1–1 shows the gyrocompass
housing, which contains the following
items:
❐True north seeking dynamically
tuned precision gyroscope and
gimbal suspension assembly.
❐Power supply board.
❐Digital and analogue control
boards.
❐RFI filter and distribution board.
It is a relatively simple operation to
install the gyrocompass and you
should be able to accomplish this
quickly without the need for special-
ised personnel or equipment. How-
ever, note that the gyrocompass
weighs 15.5kg and you must take due
care when you lift and move it.
The care that you take when you align the gyrocompass housing with the surveyed fore-aft
axis of the vessel will have a direct impact on the accuracy of heading measurements delivered
by the System. Since the Meridian Gyrocompass is an ideal source of heading information for
use by other systems on board, such as radars and satellite communication antennas, the accu-
racy of its heading measurements will have a wide impact throughout the vessel. You should

Meridian Gyrocompass
Chapter 1 Page 4 of 6 © SG Brown Issue 3.7 DPN060070
therefore take care when you install and align the gyrocompass. Refer to Section 2 for full
instructions to install, connect and align the Meridian Gyrocompass.
The only component available for user servicing is a 3.15A line fuse inside the gyrocompass
housing. In case of failure, refer to Section 5 for instructions to renew this fuse and check the
PSU board supplies.
1.1.2 Remote Control Unit
Figure 1–2: Remote Control Unit
The Remote Control Unit (RCU) provides all the functions and indicators necessary to control
and operate the Meridian Gyrocompass.
The four-character LED can show a range of information:
❐Heading in Degrees. 000.0 to 359.9
❐Latitude. 80S to 80N
❐Latitude Source
❐Speed in Knots. 00 to 90
❐Speed Source
❐Alarms and Status information
❐Seperate LED indicators show Power On and Compass Ready conditions
Refer to Section 3 for instructions to operate the Meridian Gyrocompass.
1.1.3 Auxiliary Inputs
Auxiliary inputs may be used for the Meridian Gyrocompass to apply latitude and speed cor-
rections.

1 – Introduction
DPN 060070 Issue 3.7 © SG Brown Chapter 1 Page 5 of 6
Ideally, the Meridian Gyrocompass should accept latitude and speed information from exter-
nal sources such as a GPS receiver or a speed log. However, you may supply this information
manually if external sources are not available. The advantage of using GPS or a speed log to
provide correction signals is that they allow automatic corrections to be applied without oper-
ator intervention.
Section 2 includes instructions to connect and configure the external sources of latitude and
speed information.
Section 3 includes instructions to set the latitude and speed manually.
1.1.4 Heading Outputs
The Meridian Gyrocompass is a self-contained precision navigation instrument that is capable
of supplying heading reference information simultaneously to a wide range of equipment on
board the vessel. Throughout a typical vessel, applications that can use information supplied
by the Meridian Gyrocompass include:
❐Autopilot
❐Radars
❐GPS
❐Radio direction finder
❐Course plotter and recorder
❐Satellite communication systems
❐Satellite television
To support this wide range of equipment types, the Meridian Gyrocompass can supply heading
information simultaneously through multiple channels using any of the common transmission
formats.
Refer to Section 3 for a description of the available output channels and their data formats.
1.2 PRINCIPLE OF OPERATION
In the absence of external influences, a free-spinning gyroscope will try to maintain a fixed
orientation in space. The Meridian Gyrocompass exploits this property and uses gravity con-
trol and earth rotation to align the gyroscope spin axis with the meridian, i.e. the true north
direction.
Refer to Appendix A for the general theory of gyrocompass operation.

Meridian Gyrocompass
Chapter 1 Page 6 of 6 © SG Brown Issue 3.7 DPN060070

2 – Installation
DPN 060070 Issue 3.7 © SG Brown Chapter 2 Page 1 of 16
2 INSTALLATION
To obtain the best performance from the Meridian Gyrocompass you must take care when you
install and connect it. This section includes all the information and instructions you will need
to complete these tasks.
You should read this section carefully and understand the important instructions that it con-
tains before you begin to install or connect the equipment.
2.1 Unpacking and Inspection Page 2
Explains the inspection checks that you should perform as you unpack the Meridian Gyrocom-
pass.
2.2 Physical and Electrical Installation Page 3
Choose a suitable location to install the Meridian Gyrocompass. Connect the system to an
electrical supply and to external equipment.
2.3 Alignment Page 12
The care that you take as you align the Meridian Gyrocompass with the fore-aft datum on the
vessel will have a direct influence upon its accuracy.

Meridian Gyrocompass
Chapter 2 Page 2 of 16 © SG Brown Issue 3.7 DPN 060070
2.1 UNPACKING AND INSPECTION
WARNING
The Meridian Gyrocompass weighs 15.5kg. To avoid personal injury, take proper pre-
cautions if you lift or move the equipment.
CAUTION
The Meridian Gyrocompass includes precision components and bearings. To avoid
causing damage to any part of the System, handle all items with care.
Retain the original transit cases so that you can use them to transport the system when
necessary. You will void the warranty if you use improper packing during transporta-
tion.
CAUTION
Severe damage to the Meridian Gyrocompass can occur if you move the gyrocompass
while the rotor is still spinning without the servo system in operation.
Note that the gyro rotor continues to spin for approximately five minutes after you
power-off the system.
To avoid potential damage to the Meridian Gyrocompass, always allow a period of five
minutes after power-off for the gyro rotor to come to rest before you attempt to move
the gyrocompass.
The Meridian Gyrocompass undergoes a full series of electrical and mechanical tests during
manufacture and before dispatch. The packing case has a special design to protect the contents
against shock during transit so that the equipment should arrive without damage or defect.
As soon as possible after you have received the system, check all items against the shipping
documents. Inspect all sub-assemblies carefully to check for any damage that may have
occurred during transportation. If you see any damage file a claim with the carrier and imme-
diately notify SG Brown.
To avoid loss or damage to any components of the system, store all sub-assemblies safely in
the transit case until you need to install them. Obey the storage temperature limits listed in
Section 4.
Notify SG Brown immediately if there are any components missing from the shipment.
The title page of this Manual lists the contact details for SG Brown.

2 – Installation
DPN 060070 Issue 3.7 © SG Brown Chapter 2 Page 3 of 16
2.2 PHYSICAL AND ELECTRICAL INSTALLATION
2.2.1 Selecting a location
There are certain guidelines that you should follow to install the Meridian Gyrocompass suc-
cessfully:
CAUTION
During operation, the gyrocompass must remain level to within ±45°. If it experiences
tilt greater than 45° in any direction, it will ‘topple’. Safety routines in the gyro software
will then power-off the gyro rotor and show alarm conditions on the RCU. To restore
normal operation, establish a level operating attitude and then power-on the gyrocom-
pass normally.
Never apply a tilt of more than 45° with the gyro rotor spinning or during the gyrocom-
pass initialisation procedure. Note that the gyro rotor continues to spin for approxi-
mately five minutes after you power-off the System.
❐The gyrocompass weighs 15.5kg. Choose a mounting location that is level, flat and suffi-
ciently strong to support the unit without flexing or experiencing extreme vibration. The
mounting location can be open, as on a chart table, or enclosed within a cabinet.
CAUTION
If you install the gyrocompass in an enclosed space, make certain there is sufficient
ventilation and circulation of free air to allow effective cooling.
❐Choose a location that protects the Meridian Gyrocompass from damage.
❐Do not install or operate the Meridian Gyrocompass where the ambient temperature could
fall below 0°C or rise above +45°C, or where rapid changes of temperature can occur.
❐Do not install the Meridian Gyrocompass close to strong mechanical or electrical noise
sources, or in a location susceptible to vibration or shock.
❐Allow a minimum distance of 0.4m between the gyrocompass housing and any standard
magnetic compasses.
❐Choose a location that allows convenient access to install, connect and service the Merid-
ian Gyrocompass. Refer to Figure 2–6 for clearance dimensions.

Meridian Gyrocompass
Chapter 2 Page 4 of 16 © SG Brown Issue 3.7 DPN 060070
2.2.2 Gyrocompass installation
You must align the Meridian Gyrocompass so that its fore-aft axis is parallel to the fore-
aft datum on the vessel. Any misalignment between the gyrocompass housing and the
vessel will have a direct effect on the accuracy of heading measurements delivered by
the system.
To install the Meridian Gyrocompass you will need the following tools:
❐Screwdriver 5.5mm × 150mm
❐Screwdriver 3mm × 75mm
❐Nut spinner 5.5mm
❐Combination spanner 10mm
❐Hexagon key 2mm
❐Adjustable spanner opening to at least 33mm
❐Suitable cables for the installation as indicated in Table 2–1.
There should be no need to remove the gyrocompass cover during installation. You may gain
access to make power and signal connections by removing the gland plate assembly, compris-
ing the Gland Plate and the Distribution Board. There is a removable panel on the top of the
gyrocompass that allows access to the internal DIP switches and a 60-way test connector.
1. During installation you must align the Meridian Gyrocompass so that its fore-aft axis is
parallel with the fore-aft datum on the vessel. It is not necessary for the gyrocompass to be
on the vessel centre line. There are alignment marks on the base of the Meridian Gyrocom-
pass to help you achieve the correct alignment.
2. Three elongated securing holes machined into the gyrocompass base allow you to make
fine adjustments to alignment after installation. With the gyrocompass positioned accu-
rately, mark the supporting surface with the centre positions for the three securing holes.
Refer to Figures 2–5 and 2–6 for dimensions.
Table 2–1: Suitable cable types
Purpose Suitable cable
Power supply 7/0.5mm (1.5mm2) HOFR sheathed to BS6883
Synchro heading output
Resolver heading output
Stepper S-code output
7/0.4mm (1.0mm2) butyl or EP rubber insulated, CSP
sheathed, wire braided and CSP oversheathed.
Serial data heading output
Serial data speed input
Serial data latitude input
1/0.85mm (0.6mm2) twisted pair, butyl or EP rubber insulated,
CSP sheathed, wire braided and CSP oversheathed.

2 – Installation
DPN 060070 Issue 3.7 © SG Brown Chapter 2 Page 5 of 16
3. Remove the gyrocompass and drill three 8.5mm diameter holes, using the marks you have
just made on the supporting surface as hole centres. Deburr the holes and remove any
swarf.
4. Reposition the gyrocompass and align it to the fore-aft datum. Use three M8 bolts with
washers and nuts to secure the gyrocompass in position.
5. Connect a 24V electrical supply (acceptable range 18V to 36V DC) to the Meridian Gyro-
compass at J1, the three-pin power inlet on the Gland Plate. Figure 2–1 shows the Gland
Plate.
Figure 2–1: Gyrocompass gland plate
CAUTION
Do not make any connections to the gyrocompass with power on the supply cable.
6. Connect the ship’s safety ground to the earthing stud adjacent to the power connector.
7. Make all necessary signal connections to the Meridian Gyrocompass at the Distribution
Board. The Distribution Board accepts open tails for all connections. Pass cables through
available glands in the Gland Plate. Glands A, D, E, F and J (identified in Figure 2–5)
Fuse
3.15AF
Compass Min. Safe Dist.
Build Standard No.
Serial No.
Mfg. Date
m
Watford, England.
CAUTION
Before removing the cover or the RCU
unit, remove the gland plate and
disconnect the RCU cable (TB1/17-22)
from the distribution board.
Gland plate release screws
Cover plate release screws

Meridian Gyrocompass
Chapter 2 Page 6 of 16 © SG Brown Issue 3.7 DPN 060070
accept cables up to 18mm diameter, while all other glands accept cables up to 14mm diam-
eter. Refer to Figure 2–3, and Tables 2–3 and 2–4 for cable connection details.
8. To maintain EMC compliance, connect all the wire braiding on the cables to the grounding
posts on the inside surface of the Gland Plate as shown in Figure 2–2.
Figure 2–2: Termination of wire braided cables
9. Refit the Gland Plate, making certain there are no trapped wires or cables.
Figure 2–3: Gyrocompass distribution board