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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WhentheMTi/MTxisinMeasurementState,theinternalDSPcontinuouslyrunsalooproughlyaccordingto
the above diagram. The triggering can be generated by device internal sampling triggers, or by external
software triggers (polling), or even hardware triggers (normally not recommended). For more information
abouttriggeringseesection5.5.
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Thetimedelaybetweenaphysicalevent(e.g.anorientationchangeoracceleration)isdictatedbytwofactors;
1. Internalacquisitionandcalculationtime
2. Serialtransmissiontime
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Theinternalacquisitionandcalculationtimeisdependentonthescenarioandtheoutputmode.Thefollowing
tableshowstheinternalacquisitionandcomputationtimesofallscenariosandoutputmodes.SincetheXsens
Kalman Filter applies different calculations depending on the data available, the computation time is not
constant.Inthetablebelowthelongest(worstcase)computationtimesarelistedsincetheseareusuallyof
particularimportanceforcontrolapplications.Internalacquisitiontimeofrawdatais0.19ms.
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Scenario+outputmode Calibrateddata
acquisitionand
computationtime
Orientationworstcase
acquisitionand
computationtime
XKF‐3scenario
–
Human 0.31 ms 2.55ms
XKF‐3scenario
–
Human_largeaccelerations 0.31 ms 2.55ms
XKF‐3scenario
–
Machine 0.31 ms 2.55ms
XKF‐3scenario
–
Machine_nomagfield 0.31 ms 2.01ms
XKF‐3scenario
–
Marine 0.31 ms 2.55ms
There is no difference between the internal acquisition and computation time of orientation data and
calibrateddata/orientationdatatogether.
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Theserialtransmissiontimecaneasilybecalculated:
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timeontransmissi
sbitsbaudrataioncommunicat
bytebitsmessageinbytestotal
_
)/(_
/10*___
=
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ThesetwofactorswillbediscussedusingtheexampleofthetwocommonoutputmodesoftheMTiandMTx.
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The bytes in the message consist of the Preamble, BusID, MessageID, length indicator, data itself and the
checksum:
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PREAMBLE BID MID LEN DATA CHECKSUM
Sampling
ADC
Sensor
Fusion
Output
Triggering
Hardware/
softwaretriggers
Physical
Calibratio
n
Data
Hardware
triggeronly