Freescale Semiconductor FRDM-FXS-MULTI 데이터 시트
MMA8652FC
Sensors
10
Freescale Semiconductor, Inc.
3
Terminology
3.1
Sensitivity
The sensitivity is represented in counts/g.
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In ±2 g mode, sensitivity = 1024counts/g.
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In ±4 g mode, sensitivity = 512counts/g.
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In ±8 g mode, sensitivity = 256counts/g.
3.2
Zero-g offset
Zero-g Offset (TyOff) describes the deviation of an actual output signal from the ideal output signal if the sensor is stationary. A
sensor stationary on a horizontal surface will measure 0 g in X-axis and 0 g in 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 0x00, data expressed as a 2's
complement number). A deviation from ideal value in this case is called Zero-g offset.
sensor stationary on a horizontal surface will measure 0 g in X-axis and 0 g in 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 0x00, data expressed as a 2's
complement number). A deviation from ideal value in this case is called Zero-g offset.
Offset is to some extent a result of stress on the MEMS sensor, and therefore the offset can slightly change after mounting the
sensor onto a printed circuit board or after exposing it to extensive mechanical stress.
sensor onto a printed circuit board or after exposing it to extensive mechanical stress.
3.3
Self-Test
Self-Test can be used to verify the transducer and signal chain functionality without the need to apply external mechanical
stimulus.
stimulus.
When Self-Test is activated:
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An electrostatic actuation force is applied to the sensor, simulating a small acceleration. In this case, the sensor outputs will
exhibit a change in their DC levels which, are related to the selected full scale through the device sensitivity.
exhibit a change in their DC levels which, are related to the selected full scale through the device sensitivity.
•
The device output level is given by the algebraic sum of the signals produced by the acceleration acting on the sensor and by
the electrostatic test-force.
the electrostatic test-force.