LSM6DSTX datasheet(16/175 Pages) STMICROELECTRONICS

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4.6

Terminology

4.6.1

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 (see Table 2).

An angular rate gyroscope is a 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 (see Table 2).

4.6.2

Zero-g and zero-rate 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 measures 0 g on

both the X-axis and Y-axis, whereas the Z-axis measures 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 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 “Linear acceleration zero-g level change vs. temperature” in Table 2. 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 (see Table 2).

LSM6DSTX

Terminology

DS14039 - Rev 1

page 16/175

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