Determination of the parameters of an electrodynamic transducer

One of the most interesting areas of contact between the studies of electrical and mechanical systems is that exemplified by the electrodynamic transducer. In such a device the electrical and mechanical aspects profoundly influence one another, so that in problems of performance and design it is frequently necessary to measure the parameters of the system. The electrodynamic transducer, whose mechanical system consists of mass, compliance and damping having a single degree of freedom and whose coil has inductance and resistance, is first treated in detail via its equivalent circuit. This therefore consists, over the working frequency range of the transducer, of five elements and it is to the measurement of these, and a sixth, the constant of transduction, that the bulk of the paper is devoted. Several methods of measurement of each of the mechanical parameters are described allowing the principle of intercomparisons of different determinations to be used. The methods described for measuring the electrical parameters, believed to be original, readily accommodate the frequency dependence, which due to eddy-current effects sometimes occurs in practice. Brief mention is made of some of the experimental techniques which have been successfully used for the measurements and some consideration is given to the factors which limit the accuracies attainable in practice.