Accelerometer sensors exhibit several types of limitations, including offset error, drift error, sensitivity
error, and noise. Offset and sensitivity errors are corrected by calibrating the sensor against known
accelerations. Drift errors are typically related to temperature changes but can be minimized by
maintaining a consistent environment temperature. Noise is the random variations introduced into the
sensor system. Oversampling algorithms and signal filters minimize the effects of sensor noise. Each
of these sensor errors affect how the data is processed into a usable result. For example, integrating
acceleration to determine displacement is heavily skewed due to the drift and noise characteristics of
the sensor.
Accelerometer sensors detect translation motion within the axis of the proof-mass. Rotational motion
causes centripetal acceleration that is interpreted as translational motion by the accelerometer. For
example, spinning about the z-axis will cause acceleration in the x/y axes even though there is no
translational motion in the x/y plane. A gyroscope sensor, which measures rotational velocity about an
axis, is needed to discern rotational motion from translational motion. An accelerometer sensor and
gyroscope sensor are required to determine the six variables of 3D motion. This combination of
sensors is considered an inertial measurement unit (IMU) system. Some IMU systems include an
additional magnetometer sensor (compass) and GPS to further aid the calculations of motion.
Gulf Coast Data Concepts
Page 25
X16-5, Rev New
Figure 23: Simplified MEMS Accelerometer Design (L) and Actual MEMS
Accelerometer (R)
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