Abstract
Natural aging of commercial triaxial low-g MEMS accelerometers, manufactured by surface micromachining, was evaluated in terms of changes of their offset voltages and scale factors, assigned to each sensitive axis. Two pieces of two models of triaxial accelerometers (ADXL 330 and ADXL 327 by Analog Devices Inc.) with analog outputs were tested within a period of ca. 4.5 years. Two different computer-controlled test rigs were used for performing relevant experimental studies, employing tilt angles as the reference source. Methodology of determining the proposed indicators of aging was based on cyclic repetition of the calibration procedure for each accelerometer. Changes of the output signals of the tested accelerometers were observed, resulting in respective indication errors of ca. 0.8% or even 2.2% while related to determining tilt. Since the accelerometers were operated under mild conditions while tested, much bigger errors are to be expected in the case of harsh conditions. Both pieces of ADXL 330 accelerometers ceased to operate properly within the testing period, approximately at the same time, for no apparent reason; thus, it is recommended to introduce redundancy in relevant reliable measuring circuits by doubling the number of the applied accelerometers.
Highlights
Since their introduction to the market as detectors in automotive airbag systems in the 1980s, Microelectromechanical System (MEMS) accelerometers have been employed in an ever-increasing number of mechatronic and electronic systems
It was accepted that the subscripts of the offset ox::z and the scale factor sx::z are consistent with the particular sensitivity axes of the accelerometers
Even though values of errors Δmx::z and δmx::z listed in Table 3 are of the same magnitude for all the tested accelerometers, only one piece of them (ADXL 327#1) revealed some systematic tendencies in changes of the analyzed parameters that can be attributed to aging: the offset (Figure 6) as well as the scale factor (Figure 9) took on values perceptibly different than the original ones; the maximal error (Figure 12) features a tendency to increase its value over time, being insignificant at the beginning of the study
Summary
Since their introduction to the market as detectors in automotive airbag systems in the 1980s, Microelectromechanical System (MEMS) accelerometers have been employed in an ever-increasing number of mechatronic and electronic systems. E.g., in smartphones [1] and the like (tablets, photo cameras, and smartwatches [2]), may not be so strategic, there are other devices, e.g., automotive safety systems like the said airbag or a new generation of motorcycle ABS [3], or even diving instruments [4], where MEMS accelerometers are directly responsible for the protection of human life—the related aging effects become as critical as the results of aging of, e.g., social infrastructures such as bridges and other essential infrastructure systems [5]; health monitoring of such structures is a solution increasing safety of their users [6, 7]. If calibration was not repeated within a longer period of time, it would be advantageous to take into account errors due to aging and compensate for them
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