Using Accelerometers for Measuring Rotational Degrees-of-Freedom

In many applications, such as structural testing or vehicle collision studies, rotational data are required. Modal analysis will mainly use it to identify rotational degrees of freedom (DOFs), where crash testing will mainly look into rotational inertia. Measuring rotational acceleration can be done by computing measurements from linear sensors, but this leads inevitably to an increase in measurement errors. The Kistler quartz rotational accelerometers, Types 8838 and 8840 have been developed for direct measurement of angular acceleration. In the first part of this article, we are going to compare the internal design of the rotation accelerometers Type 8838 and 8840 to solutions based on computing measurements from linear sensors. We will look into optimization of the assembly as well as a calibration procedure. In the second part, we will focus on how the rotational sensors have been used to identify and investigate shaker planar rotation. We will then look into how these undesirable planar rotations can influence linear sensor measurement.