Abstract
The main errors of MEMS accelerometers are misalignments of their sensitivity axes, thermal and long-term drifts, imprecise factory calibration, and aging phenomena. In order to reduce these errors, a two-axial tilt sensor comprising a triaxial MEMS accelerometer, an aligning unit, and solid cubic housing was built. By means of the aligning unit it was possible to align the orientation of the accelerometer sensitive axes with respect to the housing with an accuracy of 0.03°. Owing to the housing, the sensor could be easily and quickly recalibrated, and thus errors such as thermal and long-term drifts as well as effects of aging were eliminated. Moreover, errors due to local and temporal variations of the gravitational acceleration can be compensated for. Procedures for calibrating and aligning the accelerometer are described. Values of thermal and long-term drifts of the tested sensor, resulting in tilt errors of even 0.4°, are presented. Application of the sensor for monitoring elevated loads is discussed.
Highlights
MEMS accelerometers are currently widely used in many electronic and mechatronic devices for a number of purposes primarily related to the sensing of linear acceleration, and vibration [1], mechanical shock [2], and one-axis tilt, i.e., inclination [3], or two-axial tilt [4]
Despite numerous advantages of these microsensors, including low price, robustness, small size, high shock-resistance and easy integration with electronics, there are a few disadvantages that characterize their performance. These are mainly: misalignments of the sensitivity axes [8]; thermal and long-term drifts of the output signals [9]; errors related to factory calibration of the accelerometer and aging of the silicon structure [8]; and attenuation of amplitude and phase shift over frequency [10]
Physical alignment enables a precise positioning of the accelerometer with respect to the sensor housing, i.e., the particular accelerometer sensitivity axis is oriented in such a way that it is either parallel or perpendicular to the housing external faces
Summary
MEMS accelerometers are currently widely used in many electronic and mechatronic devices for a number of purposes primarily related to the sensing of linear acceleration, and vibration [1], mechanical shock (jounce) [2], and one-axis tilt, i.e., inclination [3], or two-axial tilt [4]. Despite numerous advantages of these microsensors, including low price, robustness, small size, high shock-resistance and easy integration with electronics, there are a few disadvantages that characterize their performance These are mainly: misalignments of the sensitivity axes (including their non-perpendicularity) [8]; thermal and long-term drifts of the output signals (affecting both the offset and the scale factor) [9]; errors related to factory calibration of the accelerometer and aging of the silicon structure [8]; and attenuation of amplitude and phase shift over frequency [10]. The following errors were fully eliminated: imprecise factory-calibration of the offset and the scale factor for each sensitivity axis of the accelerometer, as well as aging effects of the sensor-chip
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