Instruction Manual

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Page40
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GNAV540UserManual
7430‐0808‐01Rev.B
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inthehorizontalplane.UsingNAV‐V ironeffectsIEW2.2,thehardandsoft canbeviewedbyselectingthe
ationMenu
MisalignmentoptionontheConfigur emagneticci
Forcalibrationinstructions,referto
,andviewingth rcleduringthecalibration.
AligningtheMagnetometeronpage57.
MagnetometerAlignmentUsingCode
Theunitprovidesacommandinterfaceforinitiatingthehardiron/softironcalibrationwithoutusingNAV‐VIEW
2.2.Todoso,senda commandtoinitiatethecalibration,andthenrotatetheusersystem360degrees.The C
WC W
dhastwooptions:auto‐terminationandmanualtermination.
• Withauto‐termination,theunittrackstheyawmovementandafter380degreesofrotationreturnsthe
calibrationcompleteresponse,

comman
CC.Theauto‐terminationsequencecanfalselyterminateifthe360degree
so
rotationisnotcompletedwithintwo(2)minute fthe
WCcommandinitiation.
• Manualterminationrequiressendingasecond
WCcommandwiththeterminationcodeinthepayload.
Manualterminationisagoodoptionwhentheusersystemmovesveryslowly(e.g.,largemarinevessel)and
te
completingthe360degreerotationmayrequiremorethantwominu s.
ThestatusofthemagnetometercalibrationisindicatedbythesoftwareErrorÆdataErrorÆmagAlignOutOfBounds
errorflagavailableinthe
T0packet.YoucanaccessthehardIronScaleRatioandsoftIronScaleRatiocalibrationdata
asconfigurationfieldsinNAV‐VIEW2.2,orbyusingthecommunicationprotocol.Also,thesoftwareErrorbitofthe
ftw
masterFailbytewithintheBITwordistransmittedineverymeasurementpacket.Whentheunithasnotbeen
properlycalibrated,thisso areErrorbitwillbesettofail(high).
Thecalibrationcomplete(
CC)commandresponsemessagecontainstheXandYhardironbias,aswellasthesoft
ironratio.Thisinformationcanbeinterpretedtogiveanindicationofthequalityofthecalibration.Formore
informationonthehardironbiasandsoftironratioeffectsreferto
CompensationforMagneticFieldsonpage39.
Referto
Chapter9.CommunicatedwiththeGNAV540UnitfordetailsofWCandCCcommands.
InstallationGuidelines—ExternalMagnetometer
FieldInstallation
• Forapropercalibrationandalignment,theGNAV540unitmustbeinstalledinitsoperatingenvironment,
whichitwillbeused.
suchasthelandvehicleoraircraftin
• Ifusinga
nexternalmagnetometer:
o Themagnetometermustbemountedatleast24”awayfromlargeferrousobjectsandfluctuating
magneticfields.Failuretolocatethemagnetometerinacleanmagneticenvironmentwillaffectthe
attitudesolution.
o Configuringthepitchandleveloffsetsofthemagnetometermustbeperformedbeforecalibrating
theGNAV540unit.
EMIProtectionandGrounding
• Ensurethemagnetometerisnotexposedtolargemagneticfields.Thiscouldpermanentlymagnetize
internalcomponentsanddegrademagneticheadingaccuracy.
• ForEMIprotection,themagnetometermustbeconnectedwithashieldedcablethatisconnectedtotheI/O
conn
ectorshell.
o connectorshell.
EnsurethecaseofthemagnetometeriselectricallyconnectedtotheI/O
o Theshellshouldbeelectricallyconnectedtotheuser’scableshield.