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THE VERTICAL PLANAR MOTION MECHANISM; A DYNAMIC TEST APPARATUS FOR EVALUATING CURRENT METERS AND OTHER MARINE INSTRUMENTATION
Citation:
Kalvaitis, A. THE VERTICAL PLANAR MOTION MECHANISM; A DYNAMIC TEST APPARATUS FOR EVALUATING CURRENT METERS AND OTHER MARINE INSTRUMENTATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-78/145.
Description:
The overall objective was to provide a dynamic test apparatus that can produce known, controlled high frequency dynamics for the evaluation of current meters and other marine instrumentation. Of primary interest is the establishment of flow sensor measurement capabilities, and hence, data quality in an unsteady flow environment. The culmination of this development is a Vertical Planar Motion Mechanism (VPMM) that generates three major modes of dynamics--vertical circular, vertical and horizontal--at length scales from .15 to 1.22 meters and time scales from 5 to 12 seconds. The VPMM mounts on a tow carriage which provides the steady velocity while the VPMM superimposes oscillatory motions on full size current meters. The VPMM is instrumented such that the instantaneous velocities of the test sensors and their outputs may be measured at a 20Hz sampling rate; an on-board computer allows for near-real time data analysis. This report describes the development, and wet acceptance testing of the VPMM using several types of current sensors, including an electromagnetic and acoustic variety. Current sensor dynamic response is also documented. No deleterious interactions were noted between the VPMM and the test instruments; the VPMM performance was within specifications for all conditions investigated.