LSM9DS0 Datasheet, PDF (20/74 Pages) STMicroelectronics – iNEMO inertial module 3D accelerometer, 3D gyroscope, 3D magnetometer

Terminology
3
Terminology
LSM9DS0
3.1
Set / reset pulse
The set / reset pulse is an automatic operation performed before each magnetic acquisition
cycle to degauss the sensor and to ensure alignment of the magnetic dipoles and thus the
linearity of the sensor itself.
3.2
3.2.1
3.2.2
3.2.3
3.2.4
Sensitivity
The methods to determine sensitivity and offset are given below in the following paragraphs.
Linear acceleration sensor sensitivity
Sensitivity describes the gain of the 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 time. The sensitivity tolerance describes the
range of sensitivities of a large population of sensors.
Magnetic sensor sensitivity
Sensitivity describes the gain of the sensor and can be determined by applying a magnetic
field of 1 gauss to it.
Angular rate sensitivity
An angular rate gyroscope is a device that produces a positive-going digital output for
counter-clockwise rotation around the sensitive axis considered. Sensitivity describes the
gain of the sensor and can be determined by applying a defined angular velocity to it. This
value changes very little over temperature and time.
Zero-g level
The 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 will measure 0 g for the X-axis and 0 g for the Y-axis whereas the Z-axis will
measure 1 g. The output is ideally in the middle of the dynamic range of the sensor (content
of OUT registers 00h, data expressed as two’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” (LA_TCOff in Table 3).
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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