Calibration enhancement of ShapeAccelArray technology for long term deformation monitoring applications

ShapeAccelArray (SAA) provides precise 3D position along a continuum using hundreds of low cost MEMS sensors. The technology has been applied to long term soil monitoring applications, where long-term accuracies in the 50 part-per-million (ppm) range have been achieved. Industrial demand for the technology in structural monitoring applications where 10 ppm would be desirable has magnified the importance of modelling and compensating for temperature sensitivities of each sensor. In such applications, dramatic temperature changes are possible, unlike the relatively stable, sub surface environment. Pure silicon MEMS devices have exceptional mechanical characteristics and low temperature coefficients, but achieving 10-50 ppm accuracy requires exceptional characterization and compensation for the nonlinear response of gain and offset to temperature. An automated polynomial fit temperature calibration procedure was developed to improve the reliability of SAA measurements over an extended temperature range. This paper includes a discussion of issues and problems encountered in developing the nonlinear calibration process, and compares the results with those obtained using linear calibration techniques.