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].