Total Motion (6 DOF) Accelerometer Calibration Utilizing Known Dynamic Behavior

Six degree-of-freedom (DOF) dynamic accelerometer calibration allows for simultaneous, accurate calculation of primary and cross-axis sensitivities of an array of transducers. This calibration method relies on measured motion of geometrically well-defined structure with known dynamic behavior. Using an array of reference accelerometers, the global motion of a calibration platform is defined. Unlike traditonal calibration techniques, where a single DOF is excited while cross-axis DOF are assumed negligible, this method forces and measures all six DOFs. For low frequency calibration, a platform designed to act as a rigid body over the frequency range greatly simplifies post processing. Simple geometric transformation matrices allow extrapolation of the motion at any site (corresponding transducer-under-test (TUT) location) on the structure. However, at high frequencies, rigid body assumptions will not hold. Accordingly, a modal model of the calibration platform defines the structure's deformations over his extended frequency range. This dynamic model calculates accelerations at any test site. Using these accelerations and the TUT's output voltage as the system inputs and outputs, respectively, the response curves for each sensor's primary and cross-axis sensitivities result. By calibrating all six DOFs simultaneously, cross-axis contributes to a sensor's output are accounted for and do not contribute to measurement errors.