Owner's manual

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NAV440UserManual
7430‐0131‐01Rev.F
Page39
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Chapter4. MagnetometerCalibrationandAlignmentGuidelines
Thischa daligningthemagnetometerwiththe440Seriesunit.pterprovidesinformationforcalibratingan
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CompensationforMagneticFields,page39
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MagnetometerAlignmentUsingNAV‐VIEW2.2
• Code
,page39
MagnetometerAlignmentUsing ,page40
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InstallationGuidelines,page40
Thissectionprovidesguidelinestocalibrateandalignthemagnetometer.Thisinformationapplieswhen
implem
entingAHRSFunctionorNAVFunction(
AHRS440Functiononpage27,NAV440Functiononpage30).
NOTE:Foreffectivecalibrationresults,the440Seriesunitmustbeinstalledinthesystemduringthealignment
process..Ifcalibratedoutsideofthesystem,themagnetismofthesystemwillnotbemeasured.Withoutthose
values,theunitwillnotbeabletocompensatemagneticreadings:eitherheadingreadingswillbeincorrector
errormessageswillbedisplayed.
CompensationforMagneticFields
Magneticsensorsmeasuremagneticfieldswhicharethenusedtocomputeheading.Acorrectheadingangleisbased
onlyontheearth’smagneticfield.However,themagneticfieldsoftheNAV440unitandthesurroundings(suchas
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thesystem/vehicleinwhichtheunitisinstalled)arealsomeasured,whichaffectthemagneticreading.To
compensateforthesemagneticfieldsandensureaccurateheadingreadings,the440Seriesunitmustbecalibrated.
The440Seriesunitcompensatesfortheextramagneticfield(s)bytakingaseriesofmeasurementsandthen
applyingthosemeasurementstoatwo‐dimensionalalgorithm.Thealgorithmisusedtocalculatethehardironand
softironeffects,thevaluesofwhicharethenstoredasconstantsintheEEPROMoftheunit.Thoseconstantsare
usedforcorrectingthemagneticreadings,ensuringaccurateheadingoutput.Hardironeffectsareshiftsinthe
magneticfieldsfromferrousobjectsorothermagneticmaterialintheproximityofthemagneticsensor.Softiron
effectsarethechangeofdirectionofamagneticfield;thischangeiscausedbyhardironontheinputdirection.Hard
nmagneticfieldsaretemporary:softironcanbemagnetized
goperation.
ironmagneticfieldsarepermanentwhereassoftiro
andthendemagnetizedorhavevaryingeffectsdurin
Follo in
w gisanoverviewofthecalibrationprocess:
sed
1. Installthe440Seriesinthesystem(vehicle)inwhichitwillbeu
neticinterference
2. Selectanappropriatetestlocation,freeofmag
3. Runthecalibrationandalignmentprocedure
4. Setthecalibrationreadingsinthe440Seriesunit
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NOTE:Ensurethetestlocationisappropriateformagneticcalibration.Thecalibrationprocessprovidescorrections
formagneticfieldsfromfixedlocationsthatarerelativetothepositionoftheunit.Thecalibrationdoesnot
compensatefortimevaryingfields,orfieldscreatedbymagneticmaterialthatmovesrelativetothe440
Seriesunit.
MagnetometerAlignmentUsingNAV‐VIEW2.2
Duringthecalibrationprocedure,theunitmakesaseriesofmeasurementswhiletheusersystemisbeingturned
throughacomplete360degreecircle.A360degreerotationgivestheunitvisibilitytohardandsoftirondistortion