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1.5
Power supply
The compass is compatible with any DC power supply of between 8 and 30 Vdc. Typical supply
current during operation is approx. 25mA. The compass is protected against reversed
polarity.
Note that the operation of the LED adds another 10mA and that during auto-calibration the
consumption can be as high as 60mA.
Care should be taken to make sure the compass is not situated too close to the power supply, as
it's accuracy may be affected by either the iron in the mains transformer, or by magnetic field
' noise' from a switching power supply. It is not possible to cover all possible scenarios here,
and it remains up to the user to determine the suitability of a possible location for the
compass.
Note that the output from the FG1 takes several seconds to stabilize after a power is applied;
the time taken depends on the damping settings. There is a command - see section 5 –
which can be used to suppress the output after power-up.
1.6
Mounting
The compass is fixed to the chassis of the vessel or vehicle in the upright position using the fixing
holes shown in the data sheet. It does not matter which way it faces as the azimuth can be
set to North at any time the chassis is orientated North. Alternatively if the azimuth of the
chassis is known, then the FG1 may be rotated before fixing to North using a protractor.
S2 is then pressed and then the compass can be mounted on the chassis.
2 Connecting the compass to your application
2.1 Compass to a NMEA-0183 instrument
The hardware on which the NMEA-0183 standard is based on is a balanced serial protocol called
R S422. This means that two wires are need for send and two for receive.
6
NMEA OUT +
5
GND
4
NMEA IN+
+
NMEA current
source
3
NMEA IN-
-
E ternal NMEA device
Fig 2
5 of 12
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