LSM9DS1 datasheet(18/72 Pages) STMICROELECTRONICS

18 / 72 page

Module specifications

LSM9DS1

18/72

DocID025715 Rev 3

2.6

Terminology

2.6.1

Sensitivity

Linear acceleration sensitivity can be determined, for example, by applying 1 g acceleration

to the device. Because the sensor can measure DC accelerations, this can be done easily

by pointing the selected axis towards the ground, noting the output value, rotating the

sensor 180 degrees (pointing towards 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 over time. The sensitivity tolerance describes

the range of sensitivities of a large number of sensors.

An angular rate gyroscope is device that produces a positive-going digital output for

counterclockwise rotation around the 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.

Magnetic sensor sensitivity describes the gain of the sensor and can be determined, for

example, by applying a magnetic field of 1 gauss to it.

2.6.2

Zero-g, zero-rate and zero-gauss level

Linear acceleration 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 on both the X-axis and Y-axis, whereas the Z-axis will

measure 1 g. Ideally, the output is 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 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 “Linear

acceleration zero-g level change vs. temperature” in Table 3. The zero-g level tolerance

(TyOff) describes the standard deviation of the range of zero-g levels of a group of sensors.

Zero-rate level describes the actual output signal if there is no angular rate present. The

zero-rate level of precise MEMS sensors is, to some extent, a result of stress to the sensor

and therefore the zero-rate level can slightly change after mounting the sensor onto a

printed circuit board or after exposing it to extensive mechanical stress. This value changes

very little over temperature and time.

Zero-gauss level offset (M_TyOff) describes the deviation of an actual output signal from the

ideal output if no magnetic field is present.

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