Calibration of very-low-frequency accelerometers a challenging task

Abstract

The calibration of accelerometers in the very low frequency range below 1 Hz is a special challenge. Since in this frequency range the maximum acceleration that can be provided by a calibration vibration exciter is limited by its maximum stroke, the acceleration and also the electrical output of the accelerometer decreases rapidly with the frequency (12 dB/ octave). Thus the lower the frequency the bigger the problems with noise generated by the shaker bearings, electrical noise or subsonic noise coming from the laboratory floor. As a consequence the use of an excellent air bearing long-stroke vibration exciter mounted on a heavy rigid table that is well isolated from environmental vibrations is mandatory. Also an appropriate reference standard and algorithms for signal processing (Timing Problems, DC-coupling vs. High-pass filter, sine-approximation) must be chosen carefully for good calibration results. Also mechanical problems due to heavy sensors to be calibrated like seismometers, can cause trouble. This paper gives an overview over the requirements that a very-low-frequency calibration system has to meet in order to reach best measurement uncertainties. ©2010 Society for Experimental Mechanics Inc.