WARNING: MODAL TEST SENSORS CAN LIE!

摘要

This paper is intended for relatively new members of the modal testing community who may not be aware of the many ways in which the motion and force data they acquire can be wrong. The paper focuses on the accelerometers and force sensors used in modal testing. It briefly explains how these sensors work (concentrating on piezoelectric types), and points out similarities and differences between these sensors. The paper gives suggestions on selecting and using them. Mechanical difficulties such as internal resonance, attachment resonance, base bending sensitivity, lateral sensitivity and mounting are considered. Electrical difficulties such as ground loops and triboelectric noise are explored. Calibration is mentioned. Users are reminded that modal test demands electrical signals accurately representing motion and force measurements. Otherwise the finest analysis cannot deliver accurate data.