2.8.1 Accelerometer: At-Rest Noise
Accelerometer output values can drift by up to ±0.02G due to noise in the sensor itself, called at-rest noise. You must ensure that there is no impact on the ability to progress in the application if accelerometer output drift of ±0.02G occurs during a scene where the accelerometer is used. You can do this, for example, by configuring a tolerance for changes in acceleration between samplings (calling the AccelerometerReader::SetSensitivity function) or by taking similar steps.
If there is inadequate tolerance for variation in accelerometer readings—especially when the application is determining whether the system is at rest—a problem can occur where variation between characteristics of individual systems causes readings to show a constant drift of ±0.02G. This, in turn prevents the application from ever judging the system to be “at rest” no matter how long the user waits.
2.8.1.1 Accelerometer: Handling At-Rest Noise
Guideline Item |
Application progress must not be negatively affected if drift of ±0.02G occurs due to at-rest noise in the accelerometer.
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Software to Be Tested |
Applications that use the accelerometer.
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Test Method |
Check the source code.
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Pass/Fail Determination |
Passes if the player can progress in the game without issues in situations where the accelerometer is used, even in the presence of at-rest noise.
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2.8.2 Accelerometer: Sensitivity Drift
The sensitivity of the accelerometer can drift by up to ±8%, but there is no means of correcting this. After factoring in the potential offset from zero-point drift, design your application to use values 10% lower than the theoretical maximum measurable input value—even though the accelerometer can detect up to approximately 1.8G, do not design your application to anticipate values above approximately 1.62G. For example, it is prohibited to design an application where events occur when the accelerometer input value is 1.7G or higher.
Assuming the maximum sensitivity drift and zero-point drift, input values could be smaller still than this 1.62G maximum input value. However, these sensitivity drift and zero-point drift values both include an adequate margin, so your application does not need to assume a maximum input value smaller than 1.62G.
2.8.2.1 Accelerometer: Handling Sensitivity Drift
Guideline Item |
The maximum input acceleration value must be 10% less than the measurable limit.
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Software to Be Tested |
Applications that use the accelerometer.
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Test Method |
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Pass/Fail Determination |
Passes if the application can be played without problems in steps 2 and 4.
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