Selection of measurement references using the TRIP technique

The selection of multiple reference points for a modal test can be very difficult in many testing situations. If improper reference points are selected, then certain modes of the system may not be adequately excited and important modes may be poorly represented in the modal extraction process. This situation was observed for a large chiller system. In order to better identify the best set of references, a pre-modal test was performed using the Test Reference Identification Procedure (TRIP). The preliminary test was performed with a very limited set of potential reference locations selected and data obtained. Using the TRIP process, the best set of practical references were identified and the modal test performed. The results of the TRIP procedure and its usefulness in guiding this modal project are presented.