Instrument requirements for determining the dynamic properties of elastomers are particularly stringent because of the inherently low phase shift between force and displacement. Some currently available instruments and their tradeoffs are briefly discussed. A basic concept of employing matching circuits to eliminate the necessity for measuring both of the across variables, namely, position and velocity, is described, as well as the computational circuits to recover the missing variable. A scheme for compensating the phase-lagging characteristics of the transducer-amplifier combination is also presented.