Autonnic A5023 Manuale operativo
A5023/24
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A5023 A5024 FLUXGATE COMPASS USER AND
INSTALLATION MANUAL
Software releases:
V016
Hardware versions:
7310-4
Autonnic Research Ltd
UK
www.autonnic.com
A5023 A5024 manual 03.docx
Jan 2019
19 Dec 2018
A5023/24
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Table of Contents
1 Introduction and description of fluxgate compass.
1.1 Description of compass
1.2 Connections
1.2.1 A5024
1.2.1 A5023
1.2.3 Variants with suffix -CP
1.3 Switches
1.4 Indicator light
1.5 Power supply.
1.6 Mounting
2 Connecting the compass to your application.
2.1 To a NMEA-0183 instrument.
2.2 To a PC serial port.
3 Output formats available from compass.
3.1 NMEA-0183
3.2 Furuno AD-10
4 Calibrating the compass.
4.1 Why the compass needs calibrating.
4.2 Starting calibration.
4.3 Aborting a bad calibration.
4.4 Setting reference NORTH heading
4.5 Set-up suggestions
5NMEA-0183 Inputs and Outputs
6 References
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1. Introduction and description of fluxgate compass.
1.1 Description of compass.
The Autonnic NMEA compass unit is a complete component for a compass
indicating system, RADAR ‘North-up’ input or autopilot. It is housed in a
water-resistant enclosure so it can be mounted outside a steel hull. It
delivers heading data in two industry-standard forms.
The A5023 and A5024 contain a fluxgate with floating core surrounded by
high-precision interface circuits which, together with the special
clockwise/anticlockwise and offset nulling sequence allow a
microprocessor to acquire a binary value from two orthogonal sensors of
the horizontal component of the Earth’s magnetic field. The processor
calculates the vector from these values, uses a calibration table to correct
for local field disturbance errors, offsets the result and then presents the
data in a manner which has been requested. Such requests alter the
frequency of the data, the degree of filtering and the offset value.
Calibration sequences can also be commanded.
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1.2 Connections
1.2.1 A5024
Conductor
Colour
Type
Function
1
Red
P
+Supply 8-30v
2
Yellow
O
NMEA OUT+
3
Brown
I
NMEA IN-
4
White
I
NMEA IN+
5
Black
P
GND
6
Blue
O
Furuno AD-10 Clock
7
Violet
O
Furuno AD-10 Data
8
Green
P
GND
Screen
Not connected
NOTE 1 Conductors 5 and 8 are connected together inside the A5024
NOTE 2 Wiring does not use the same colours as the A5022
1.2.2 A5023
Conductor
Colour
Type
Function
1
Red
P
+ Supply 10-30V
2
Yellow
I
NMEA IN -
3
Blue
O
NMEA IN +
4
Green
I
NMEA IN+
5
Screen
P
GND
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1.2.3 Variants with suffix -CP
A5023
Conductor
Colour
Type
Function
1
Red
P
+ Supply
2
Yellow
I
NMEA IN +
3
Blue
P
GND and NMEA IN -
4
Green
O
NMEA OUT +
NOTE Cable foil and drain wire internally NOT connected to GND
1.3 Switch Inputs
S1
S2
Fig 1
Except for variants with suffix -S, two push-button switches are provided for
calibrating the compass in the field.
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When the A5023-24 is viewed from the front face with the LED facing, then
Switch 1 is on the right and Switch 2 is on the left.
1Switch 1: Start the auto-calibration process
2Switch 2: Set reference NORTH heading. The A5024/4
must be mounted upright but at any azimuth. Pressing S2 sets the
heading to zero and so can be done when the whole installation is
headed North.
3Both together Pressing both together for at least one second causes
the auto-calibration process to halt and restores the previously saved
calibration values.
1.4 Indicator light
A blue light indicates three states of the A5023-24.
State 1 Uncalibrated long flash
State 2 In the process of calibration continuous
State 3 Calibrated short flash
After the reset command, $PATC,IIHDG,0CV<CR><LF>, the compass is
uncalibrated and will have a long flash.
Note that the LED can be turned off and on by the DLED command –see section
5.
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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 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 compass
may be rotated before fixing to North using a protractor. S2 is then pressed and
then the compass can be mounted on the chassis.
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A5022
COMPORTD
CONNECTOR
2
3
5
4NMEAIN+
3NMEAIN-
5GND
6NMEAOUT+
7GND
+POWER
SOURCE -1+8-30V
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 RS422. This means that two wires are need for send and two for
receive.
Fig 2
Note that the GND wire is used for the current return path. This might be
shared with the NMEA- wire in some installations.
2.2 Compass to a PC serial port
In many cases the wires can be joined directly as shown in Fig 2.
Alternatively use the Autonnic A3036 serial interface unit.
Fig 3
External NMEA device
6 NMEA OUT +
4 NMEA IN+
3 NMEA IN-
5 GND
NMEA current
source
+
-
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3 Output formats available from compass
3.1 NMEA-0183
The serial output format is: 4800 Baud, 8 data bits, 1 stop bit, no parity.
The compass sends information using the standard NMEA-0183 sentence
‘HDG’: Magnetic Heading, Deviation, and Variation. But note that the
information of Deviation and Variation is not sent and so blank fields are
defined by consecutive commas. In the A5024/4 the sentence may have
one of several forms typically of the general form:
$HCHDG,hhh.h etc
Where hhh.h is the magnetic heading from 000.0 to 359.9 degrees
Also the Rate-of-turn data is sent either with or without the heading
sentence.
For a complete list of output formats available see Section 5.11
3.2 Furuno AD-10 -A5024 only
The compass has a separate, dedicated output in Furuno AD-10 format.
This is a proprietary 4 character serial format, which gives heading in
degrees and tens of minutes. The string 0872 represents the heading 87°
20’ so that the precision is to 1/6 of a degree. At the same time the
A5024 would be also sending the NMEA data to a precision of 1/10 of a
degree.
480µs
100ms minimum
Duration of data is 16 clocks each
high=low=30µs. Total = 480µs.
Frequency of data packets is set by
the interval command. Max = 10Hz
Clock
Data
Fig 4
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4 Calibration
4.1 Why the compass needs calibrating
When any compass is installed the magnetic characteristics of the whole
installation affect the way the Earth’s field reaches the detector inside the
device. Each individual installation will be different and so the A5023 and
A5024 are equipped with an auto-calibration routine which corrects for
these installation distortions.
4.2 Starting calibration
-A NMEA-0183 command can be sent to initiate the process –
section 5.2.9
OR
-Switch 1 can be pressed.
There are two compass calibration techniques in common use:
1Constant angular velocity
2Double rotation without constant velocity.
The Autonnic compasses use the first method. The process consists of
rotating the whole installation in the Earth’s field so that both permanent
magnets and induced magnets are corrected. The method used is the
single turn at a constant rate and this rate should be in range 60 to 180
seconds for the full 400 degrees needed. The whole arrangement is turned
at constant angular velocity because the method relies on applying a
correction when the heading measured is uneven with time.
The second method is not used by us. Autonnic has evaluated the method
which uses a mathematical model of an ideal compass and treats errors as
arising from distortion due to magnetic objects. The ideal error plot of the
field vector would be a circle with no offset from the origin. Permanent
magnets (‘hard’) have the effect of shifting the centre from the origin and
induced magnets (‘soft’) modify the circle into an ellipse. The results of
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