LSM303DLHC Datasheet, PDF (14/43 Pages) STMicroelectronics – Ultra compact high performance e-compass 3D accelerometer and 3D magnetometer module

Module specifications
LSM303DLHC
2.6
2.6.1
2.6.2
Terminology
Linear acceleration sensitivity
Linear acceleration sensitivity describes the gain of the accelerometer sensor and can be
determined by applying 1 g acceleration to it. As the sensor can measure DC accelerations,
this can be done easily by pointing the axis of interest towards the center of the Earth,
noting the output value, rotating the sensor by 180 degrees (pointing to the sky) and noting
the output value again. By doing so, ±1 g acceleration is applied to the sensor. Subtracting
the larger output value from the smaller one, and dividing the result by 2, leads to the actual
sensitivity of the sensor. This value changes very little over temperature and also very little
over time. The sensitivity tolerance describes the range of sensitivities of a large population
of sensors.
Zero-g level
Zero-g level offset (TyOff) describes the deviation of an actual output signal from the ideal
output signal if no acceleration is present. A sensor in a steady-state on a horizontal surface
measures 0 g in the X axis and 0 g in the Y axis whereas the Z axis measures 1 g. The
output is ideally in the middle of the dynamic range of the sensor (content of OUT registers
00h, data expressed as 2’s complement number). A deviation from the ideal value in this
case is called Zero-g offset. Offset is, to some extent, a result of stress to the MEMS sensor
and therefore the offset can slightly change after mounting the sensor onto a printed circuit
board or exposing it to extensive mechanical stress. Offset changes little over temperature,
see “Zero-g level change vs. temperature”. The Zero-g level tolerance (TyOff) describes the
standard deviation of the range of Zero-g levels of a population of sensors.
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