Vol. 141, No. 6, June 2012, pp. 106-118

Abstract: An implantable displacement sensor for postoperative stability evaluation of THA (Total Hip Arthroplasty) or TKA (Total Knee Arthroplasty) implants proposed in our previous paper [5] features a self-calibrated algorithm to balance the DVRT bridge in the sensor before the measurement starts. The calibration process is accomplished by adjusting the frequency and phase of the output signal of the bridge iteratively until the bridge output is 0. Whether or not the calibration can be successfully accomplished depends on the errors of the intermediate parameter adjustments occurring in the calibration process. In this paper the influence of the frequency and phase adjustment errors on the calibration results is theoretically investigated. Simulation results indicate that such influence can be ignored given that the adjustment errors are in a specific range, and thus the calibration process can be simplified due to the high tolerance of the frequency adjustment error. Part of the hardware realization of the self-calibration process is also described in this paper and its feasibility is validated by the phase adjustment tolerance analysis.

Keywords: Displacement sensor, Calibration, Tolerance, Phase detector

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