User manual

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 DocumentMT0100P.N
©XsensTechnologiesB.V. MTiandMTxUserManualandTechnicalDocumentation
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7 OperatingGuidelines
7.1 Normaloperatingprocedure
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NOTE:PleasealsorefertotheQuickSetupSheetthatcameinyourDevelopmentKitpackage.
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1. Power‐onthedevice
2. Optional:checkthedeviceisusingthesettingsyouneed
3. Allowelectronicstowarmupforabout15minutesforoptimalperformance
4. Startmeasurements
5. Stopmeasurements
6. Poweroffdevice
7.2 Placementconsiderations
7.2.1 Transientaccelerations
The 3D linearaccelerometers in the MTi and MTx areprimarily used to estimate the direction of gravity to
obtainareferenceforattitude(pitch/roll).Duringlong periods(morethanafewseconds)oftransient“free”
accelerations(i.e.2
nd
derivativeofposition) theobservationofgravitycannotbemade.TheXKFsensorfusion 
algorithmstakethese effectsintoaccount,butnonethelessitisimpossible toestimate truevertical without
addedinformation.
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The impact of transient accelerations can be minimized when you take into account a few things when
positioningthedevice.
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IfyouwanttousetheMTiorMTxtomeasurethedynamicsofamovingvehicle/craftitisbesttopositionthe
measurement device at a position where you expect the least (smallest) transient accelerations. This is
typicallyclosetothecentreofgravity(CG)ofthevehicle/craftsinceanyrotationsaroundthecentreofgravity
translateintocentripetalaccelerationsatanypointoutsidethepointofrotation,whichisusuallyclosetothe
CG.Theaccelerationofthevehicleasawholecanofcoursenotbetakenintoaccount.
7.2.2 Vibrations
Forbest performancethe MTi or MTx should be mechanically isolated from vibrations as much aspossible.
Vibrationsaremeasureddirectlybytheaccelerometers.Thisisnotnecessarilyaproblem,buttwoconditions
canmakethereadingsfromtheaccelerometersinvalid;
1. The magnitude of the vibration is larger than the range of the accelerometer. This will cause the
accelerometertosaturate,whichmaybeobservedasa“drift”inthezero‐leveloftheaccelerometer.
Thiswillshowupinthe3Dorientationestimatesasanerroneousroll/pitch.
2. The frequency of the vibration is higher than the bandwidth of the accelerometer. In theory, such
vibrations are rejected, but in practice they can still give rise to aliasing, especially if close to the
bandwidth limit. This can be observed as a low frequency oscillation. Further, high frequency
vibrationsoftentendtohavelargeaccelerationamplitudes(seeitem1).
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7.2.3 Magneticmaterialsandmagnets
WhenanMTiorMTxisplacedcloseoronanobjectthatcontainsferromagneticmaterials,orthatismagnetic
byitself,themeasuredmagneticfieldisdistorted(warped)andcausesanerrorinmeasuredyaw/heading.The
earthmagneticfieldisalteredbyferromagneticmaterials,permanentmagnetsorverystrongcurrents(several
amperes).Inpractice, thedistancetotheobjectandtheamountof ferromagneticmaterialdeterminesthe