CMA3000-D0X Datasheet, PDF (27/35 Pages) VTI technologies – 3-axis accelerometer

CMA3000-D0X Series
Pin #1
Y-axis in +1 g
Z
X
position
X
Z
Y-axis in -1 g
position
Pin #1
Figure 19. CMA3000 positions for Y-axis sensitivity measurement.
Sensitivity is calculated by
Equation 3
Sens_{Y −axis}
=
Output_{Y −axis@+1g} − Output_{Y −axis@−1g}
2g
,
Earth’s
gravitation
where Sens_Y-axis is sensor’s Y-axis sensitivity in [counts/g], Output_Y-axis@+1g sensor’s Y-axis output
reading [counts] in +1 g position and Output_Y-axis@-1g is sensor’s Y-axis output reading [counts] in -1 g
position.
8.2.1 Sensitivity calibration error
Sensitivity calibration error is the difference between sensor’s measured sensitivity and the nominal
sensitivity at room temperature conditions. Error is calculated by
Equation 4
Sens_{Y −axisCalibEr}
=
Sens_{Y −axis} − Sens
Sens
⋅100% ,
where Sens_{Y-axisCalibEr} is sensor’s Y-axis sensitivity calibration error in [%], Sens_Y-axis sensor’s Y-axis
sensitivity [counts/g] at room temperature conditions and Sens is sensor’s nominal sensitivity
[counts/g].
8.2.2 Sensitivity temperature error
Sensitivity temperature error is the difference between sensor’s sensitivity at different temperatures
and the calibrated sensitivity. Error is calculated by
Equation 5
Sens_{Y −axisTempEr@T}
=
Sens_{Y −axis@T} − Sens_{Y −axis@ RT}
Sens_{Y −axis@ RT}
⋅100% ,
where Sens_{Y-axisTempEr@T} is sensor’s Y-axis sensitivity temperature error in [%] in temperature T, Sens_Y-
axis@T ^{is sensor’s measured Y-axis sensitivity [counts/g] at temperature T and Sens}Y-axis@RT ^{is sensor’s}
measured Y-axis sensitivity [counts/g] at room temperature RT.
8.3 Linearity
The needed accurate input acceleration in linearity characterization is generated using centrifugal
force in centrifuge, see Figure 20. The RPM of the centrifuge is swept so that wanted input
acceleration values are applied in parallel to the sensor’s measuring axis.
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