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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4.5.3 Un‐calibratedrawoutputmode
In un‐calibrated raw output format the “raw” readings from the 16‐bit AD‐convertersin the MTi / MTx are
outputted. This means the physical calibration model described in the previous section is not applied. This
gives you open access to the basic level of the sensor unit, but in most cases this level of use is not
recommended.However,ifyourmainpurposeisforloggingandpost‐processing,itmaybeadvantageousasit
is always possible to go back to the “source” of the signal. In this mode the device temperature is also
outputted(housingambientonly).
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NOTE:Thedatafieldsare2bytes(16bits)asopposedtothe3bytefloatsfortheotheroutputmodes.
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Temperatureoutputformat
The2 bytetemperaturedatafieldintheun‐calibratedrawoutputmodeoftheMTi/MTxcanbeinterpreted
asa16bits,2‐complementnumber.However,pleasenotethattheresolutionofthetemperaturesensorisnot
actually16‐bitbut12‐bit.
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Forexampleyoucaninterpretthe2‐bytetemperatureasfollows:
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00.00hex=0.0°C
00.80hex=+0.5°C
FF.80hex=‐0.5°C
19.10hex=+25.0625°C
E6.F0hex=‐25.0625°C
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Thetemperature‐fieldisa16‐bittwo‐complementnumberofwhich thelastbyterepresentsthevaluebehind
thecomma.Tocalculatethetemperaturevalueusetheformula:
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T=(–2
16
+x)/256 ifx≥2
15
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or T=x/256  ifx<2
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,wherexisthe16‐bitvalueoftheTempfield.
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Forexample,thevalue59120(0xE6F0)correspondswithatemperatureof‐25.0625°C.
4.6 Resetofoutputorreferenceco‐ordinatesystems
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4.6.1 Outputwithrespecttonon‐defaultcoordinateframes
InsomesituationsitmayoccurthattheMTsensoraxesarenotexactlyalignedwiththeaxesoftheobjectof
whichtheorientationhastoberecorded.Itmaybedesiredtooutputtheorientationand/orcalibratedinertial
data in an object‐fixed frame, as opposed to a sensor‐fixed frame. Four methods have been added to the
softwaretofacilitateinobtainingtheoutputinthedesiredcoordinateframes,theyarediscussedbelow.
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1. SettinganarbitraryrotationmatrixtorotateStothechosenobjectcoordinatesystemO.
Theoutputdefinitioninun‐calibratedRAWinertialdataoutputmodeis:
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MTData DATA = 
MID50(0x32)
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EachdataelementinDATAfieldis2bytes(16bit)unsignedintegers.
Seebelowforreadingthetemperaturedata
tempmagZmagYmagXgyrZgyrYgyrXaccZaccYaccX