User manual


 DocumentMT0100P.N
©XsensTechnologiesB.V. MTiandMTxUserManualandTechnicalDocumentation

17
Accelerometer Specificationamendment
±50m/s
2
(5g)(default) None,seetable1
±17m/s
2
(1.7g) None,seetable1
±180m/s
2
(18g) Noisedensity: 0.004m/s
2
/√Hz

Rategyroscope Specificationamendment
±1200deg/s(MTxdefault) Noisedensity:0.1°/s/√Hz
±300deg/s(MTidefault) None,seetable1
±150deg/s Noisedensity:0.04°/s/√Hz

Specificationsofcustomunitsmayvary.

4.5 Calibrateddataoutputmode

NOTE: This section is intended to give detailed information on the definition of the calibrated inertial data
outputmodesoftheMTiandMTx.Theoutputsequenceoftheelementsofthevectorsdefinedhereholdsfor
all interface levels (RS‐232/422, API, GUI). For more detailed information about the respective interfaces
pleaserefertotheirspecificdocumentation;
Direct ÆMTiandMTxLow‐levelcommunicationDocumentation
API  ÆMTSoftwareDevelopmentKitDocumentation
GUI  ÆMTManager

4.5.1 Physicalsensormodel
ThissectionexplainsthebasicsoftheindividualcalibrationparametersofeachMTiandMTx.Thisexplainsthe
valuesfoundontheMTTestandCalibrationCertificatethatcomeswitheachMTiandMTx.

The physical sensors inside the MTi and MTx (accelerometers, gyroscopes and magnetometers) are all
calibrated according to a physical model of the response of the sensors to various physical quantities, e.g.
temperature.Thebasicmodelislinearandaccordingtothefollowingrelation:

1
()
T
K
−
=−
T
sub
1, 1, 1,


The model really used is more complicated and is continuously being developed further. From factory
calibrationeachMTi/MTxhasbeenassignedauniquegainmatrix,K
T
andthebiasvector,b
T
Thiscalibration
data is used to relate the sampled digital voltages, u, (unsigned integers from the 16 bit ADC’s) from the 
sensorstotherespectivephysicalquantity,s.

The gain matrix is split into a misalignment matrix, A, and a gain matrix, G. The misalignment specifies the
directionofthesensitiveaxeswithrespecttotheribsofthesensor‐fixedcoordinatesystem(S)housing.E.g.
thefirstaccelerometermisalignmentmatrixelementa
1,x
describesthesensitivedirectionoftheaccelerometer
onchannelone.Thethreesensitivedirectionsareusedtoformthemisalignmentmatrix:

2, 2, 2,
3, 3, 3,
x
yz
x
yz
x
yz
aaa
aaa
A =
⎢⎥
⎢⎥
⎣⎦
aaa
⎡⎤
⎢⎥
1
00G

2
3
00
00
GG
G
⎡
⎤
⎢
⎥
=
⎢
⎥
⎢
⎥
⎣
⎦

