LSM9DS0 datasheet(20/74 Pages) STMICROELECTRONICS

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Terminology

LSM9DS0

20/74

DocID024763 Rev 2

Terminology

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

Sensitivity

The methods to determine sensitivity and offset are given below in the following paragraphs.

3.2.1

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.

3.2.2

Magnetic sensor sensitivity

Sensitivity describes the gain of the sensor and can be determined by applying a magnetic

field of 1 gauss to it.

3.2.3

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.

3.2.4

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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