ELECTROMECHANICAL MODEL FOR VIBRATING-WIRE INSTRUMENTS

A methodology to formulate equivalent electric circuits to vibrating-w ire sensors is presented, as well as examples of its application. Vibr ating-wire sensors have been used in a number of instruments built for measurement of the density and viscosity of fluids up to high pressur e and in wide temperature ranges. These instruments are based on a rig orous theoretic model describing both the mechanics of oscillation and the hydrodynamic effects arising from the presence of the sample flui d surrounding the vibrating wire. The equivalent circuits proposed in this work are essential in order to interpret the output signals of th e sensor in terms of its mechanical parameters. Design choices dictate the type of pertinent electromechanical analogy. The use of equivalen t circuits made possible the simultaneous measurement of the density a nd viscosity of fluids using one single sensor, which is a demonstrati on of a complete understanding of its behavior. (C) 1998 American Inst itute of Physics. [S0034-6748(98)04706-6].