GS720 TRANSMITTING MAGNETIC COMPASS (TMC) SYSTEM
CONTENTS
Introduction & Equipment Description, GS720 (ref: FW4720), GS502 TCM1 Sensor c/w
CABLE & PLUG (ref: FW4602), GS503 Junction Box (ref: FW4603)
Pages 1 - 2
GS720 Operating Instructions
Pages 3 - 5
NMEA 0183 Output Specification
Page 6
GS720 Faultfinding Guide
Page 7 - 8
GS720 System Block Diagram. Drawing 3379-A4-16
GS720 System Connection Details. Drawing 3379-A4-14
GS720 NMEA Unit. Dimension Drawing 3379-A3-15
GS502 TCM1 Sensor Coil c/w cable & plug. Dimension Drawing 3379-A4-13
GS503 Junction Box Dimension Drawing 3379-A4-17
GS720 Iss1 Rev 4
RJA 12/02
Gs720/hbk/ra/054
GS720 TMC System
The term TMC is used to describe a system using a sensor on the Magnetic Compass to
provide a Heading signal.
Here, the Heading signal is processed to provide a Digital Heading Display and two
independently buffered NMEA 0183 outputs.
The system is made up of the following units.
GS720 NMEA Unit Drawing 3379-A3-15 (FW4720)
The GS720 NMEA Unit is designed to fit into a Yokogawa PT500 Autopilot Standard
Frame.
The two primary functions of the unit are to provide an independent heading to the Off
Course Alarm (integrated within the Autopilot) and to provide back up Heading
information in the event of a Master Gyro failure. Both of these outputs are in the form of
NMEA 0183 serial data.
Standard features also include:
•
Deviation Correction
•
Power recognition voltage free relay contacts
•
Integral Membrane Switch panel; IP67 rated
•
LCD Display with variable illumination for night viewing
•
Heading data fail alarms
•
Power requirement less than 5 Watts at 24vDC
GS502 TCM1 Heading Sensor Drawing 3379-A4-13 (FW4602)
In most installations, Lilley & Gillie will be supplying the Magnetic Compass, to which
the TCM1 Sensor is supplied fitted and aligned to the Magnetic Compass Heading. The
GS502 TCM1 has a 1 metre cable with a 6 pole connector fitted which plugs directly into
the GS503 socket. The GS502 sensor coil can be fitted in any orientation. It is important
however to centralise the sensor coil as best as possible when fitting to the underside of
the compass.
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GS503 Junction Box Drawing 3379-A4-17 (FW4603)
This box is splash proof and will be supplied fitted onto the top shelf within the Binnacle.
On installation, run the feed cable up through the base of the Binnacle electric tubes ¾”
diameter, through the 20mm cable gland to the GS503 position. Terminate connections
within the GS503, as shown on the connection diagram 3379-A4-14.
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GS720 TMC Operating Instructions
Switch On
Press the ON/OFF key once to switch the unit ON (on condition will be signalled to an
external monitor by closure of a volt free normally open contact).
The display will show a four digit Magnetic Heading with readings to one tenth of a
degree. If no sensor is detected, display will show “Lo” and the TMC INPUT LED will
be lit and the Alarm buzzer will sound (see fault finding guide).
Press the ON/OFF key once more to turn unit off.
Illumination
With the unit switched on, four levels of illumination are available to the operator. Each
press of the ILLUM key will alter the red backlight intensity in steps as follows:Off – 1 – 2 – Maximum – Off.
Deviation
Pressing the DEV key during normal operation permits inspection of deviation status.
“nonE” = Coil calibrated: no deviation,
“dAtA” = Coil calibrated: deviation table programmed,
“rSt” = reset; ie, un-calibrated.
Calibration
Press CAL key for 5 seconds to enter calibration menu. Note that CAL LED is turned on
and will remain on for the duration of the calibration procedure. The TMC default LED
will remain lit for a few seconds before extinguishing.
1) “CAL” is displayed.
The unit is auto-calibrating the sensor coil and “CAL” is displayed for the
duration of the coil calibration.
The unit will automatically proceed to the second item on menu once coil
calibration has been completed.
If “FAIL” appears in display window, no sensor coil has been detected. In this
case, press CAL key to exit calibration mode. Check all sensor connections then
re-try. (See fault finding guide)
2) “XXX.X” is displayed.
Use the UP/DOWN arrow keys to align displayed heading with ships magnetic
compass heading. Note that each individual press will adjust the displayed
reading by 1.4°. A maximum change of +/- 180° can be applied at this stage.
Press CAL key once to proceed to final item on menu.
3) “d000” is displayed.
This is an instruction to steer 360° for the first of 12 headings in order to
programme the Deviation Table.
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3) continued:
With ship steady on 360° magnetic, (i.e., Compass heading corrected with the
deviation figure obtained from the vessels’ latest Magnetic Compass Deviation
Card), press DEV key to enter. Repeat with ship steady on Magnetic Heading
030°, then move to 060°, 090°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and
330°, pressing the DEV key when ship is steady on each heading and the compass
has been allowed to settle. Display will always indicate the heading to steer.
If a difference of more than 12.5° is registered between actual compass heading
and perceived (sensed) compass heading, the entry will be rejected and the
display will not move to the next 30° step. Check that the vessel is steering the
correct magnetic heading. If this is so, the Deviation table set-up procedure must
be aborted (see below) and calibration tried again.
When all headings have been entered successfully the display will show “End”.
If the buzzer sounds whilst on a particular heading, the Deviation table set-up
procedure must again be aborted (see below). Ensure that the vessel remains on
the heading that resulted in the buzzer sounding previously and press the CAL
key for 5 seconds to again enter the calibration menu. Follow steps 1 and 2 as
previously and then proceed to step 3 to programme the Deviation Table. All
headings should now be entered successfully and the display will show “End”.
Press CAL key to exit the Calibration Mode and resume normal operation.
To abort Deviation table set-up
If a mistake is made during the Deviation Table Programming which requires a restart
OR if a table already entered is to be Erased / Reprogrammed, then perform DEV table
erase as follows:At (or enter) calibration menu item 3.
Press UP Arrow key for 5 seconds to erase table. “nonE” is displayed until UP key is
released.
Table is erased and normal operation is resumed.
-4-
Reset to factory default settings
In the event of complete confusion for any reason, compass headings and deviation table
can be erased as follows.
Whilst in normal operation mode;
Press CAL and UP Arrow keys simultaneously for 5 seconds. “rSt” will be displayed
whilst both keys are depressed. When unit is reset the TMC DEFAULT LED will be lit.
Unusual messages
At switch on following the self test routine, but prior to any calibration, the unit may
show the following fail message(s):1) “Lo”. This indicates no signal from the compass coil; on front panel “Heading
Data Fail Alarms” section, “TMC INPUT” LED lit and alarm buzzer sounds.
2) “TMC CPU” LED lit; indicates an internal fault. Disconnect power to unit, and
then re-connect. If fault has not cleared (LED still lit), unit will have to be
returned to supplier.
3) “TMC DEFAULT” LED lit. Magnetic sensor alignment cannot be read from
internal memory. Coil calibration will be set to nominal value and deviation table
data will be set to “NONE”.
Note that messages referred to and displayed on the LCD can be in a combination of
upper and lower case characters.
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NMEA 0183 Output
Two NMEA 0183 serial output ports are available from terminals on the rear of the unit.
Outputs conform to the NMEA 0183 standard for the interfacing of Marine Electronic
Devices Version 2.30.
Data is transmitted in serial asynchronous form. The first bit is a start bit and is followed
by data bits, least-significant-bit first as illustrated below.
The sentences generated are as follows:With Deviation Table not calibrated:$HCHDM,xxx.x,M*hh<CR><LF>
$HCHDG,xxx.x,,,,*hh<CR><LF>
With Deviation Table calibrated:$HCHDM,xxx.x,M*hh<CR><LF>
$HCHDG,xxx.x,xx.x,a,,*hh<CR><LF>
Baud Rate: 4800
Output Frequency: 10 Hz
Data Form:Start Bit
Data Bit
Parity
Stop Bit
1
8 (d7=0)
None
1
D0
D1
D2
D3
D4
D5
D6
D7
DATA BITS
START
BIT
STOP
BIT
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GS720 FAULT FINDING GUIDE.
Problem: Switching GS720 on gives no display readout.
Solution: Test for 24vDC on GS720 rear connector terminals 17 (+ve) and 16 (-ve).
If voltage not present check ships DC supply.
If voltage present, switch OFF, then switch ON again.
If still no display, GS720 is defective; return to supplier.
Problem: Difference between Magnetic Compass Heading and GS720 Display.
Solution: Re-align sensor on Compass to remove error and / or perform deviation
calibration as soon as convenient.
Problem: GS720 alarms.
Solution: “Lo”. This indicates no signal from the compass coil; on front panel “Heading
Data Fail Alarms” section, “TMC INPUT” LED also lit and buzzer sounds.
Check sensor / cabling is correct. (see below).
Also ensure calibration has been carried out in accordance with the instructions
given in handbook (see pages 3 and 4).
“TMC CPU” LED lit and buzzer sounds; indicates an internal fault.
Remove power from unit, re-apply power and press ON key. If fault has not
cleared (LED still lit), unit will have to be returned to supplier.
“TMC DEFAULT” LED lit. Magnetic sensor alignment cannot be
read from internal memory. Power up alignment will be set to nominal value
and any existing deviation table will be ignored.
Perform Calibration procedure.
Sensor Testing.
The TCM1 Heading Sensor (FW4602) may be tested using a digital multi-meter as
follows.
At the terminal block in the GS503 Junction Box, disconnect the 5 cores of the 6 core
cable connecting to the GS720. With the digital multi-meter set to measure resistance,
check readings, measuring between:1) GS503 Terminal “44” and Terminal “46”. Reading should be approximately 4 ohms.
2) GS503 Terminal “45” and Terminal “48”. Reading should be approximately 6 ohms.
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Sensor Testing: continued
3) GS503 Terminal “45” and Terminal “47”. Reading should be approximately 6 ohms.
4) GS503 Terminal “47” and Terminal “48”. Reading should be approximately 6 ohms.
Insulation:
Between GS503 Terminal “44” or Terminal “46” and all other terminals (i.e., Terminal
“44” to “45”, “44” to “47”, “44” to “48”), should be 50K ohms or more.
Reconnect the 5 cores of the 6 core cable into the appropriate GS503 terminals after
successful testing of sensor.
-8-
JOHN LILLEY & GILLIE LIMITED
(INCORPORATING THOMAS WALKER)
GS720 TRANSMITTING MAGNETIC COMPASS SYSTEM
 John Lilley & Gillie Limited
Clive Street • North Shields
Tyne and Wear NE29 6LF • United Kingdom
Phone: 44 (0)191 257 2217 • Fax: 44 (0)191 257 1521
http//www.lilleyandgillie.co.uk