Underflow error in substructure testing

The main difficulty for substructure testing is to develop methods that measure moments and angular accelerations, as well as shear forces and tangential motions in order to adequately model the interface. Also the precision and consistency requirements of the test data used in substructure testing are high. Previously, the authors discussed several errors associated with substructure testing; i.e., the DOF deficiency error, the bias error, and the noise error [1]. Since the FRF's used to predict the dynamic characteristics of the combined structures are obtained experimentally, the limited dynamic range of the Analog to Digital Converter (ADC) can make the acquired FRF's incomplete; particularly, if the ADC's limited dynamic range is either insufficient or is not fully utilized by poor testing procedure. This limited dynamic range leads to an underflow error or bit dropout error in certain cases. This paper investigates the consequence of the underflow error in substructure testing.