A review of transductor principles and applications

The transductor is a fairly recently rediscovered simple electrical device of considerable adaptability and usefulness in a wide range of electric circuit techniques. The mechanical structure of a transductor is analogous to that of an iron-core transformer, but electrically the device is a d.c.-controlled ferromagnetic-core inductor of variable effective impedance, the impedance being changed by altering the magnitude of the controlling direct current. A transductor is fundamentally an a.c. apparatus which may be designed to operate, with either laminated or wound-strip core, at frequencies up to about 20 kc/s. Transductors are at present successfully employed as economically and technically efficient apparatus: (a) in heavy-current engineering for manually and for automatically operated power control in a great variety of specific modes, for measurement of heavy direct current and of high direct voltages, for remote control and for telemetering; and (b) in light-current engineering for magnetic amplification of weak direct currents for precision instrument work, computer circuits, servo mechanisms, and various other types of automatic control and of metering. The published literature of approximately the past 10 years is summarized to give a picture of transductor performance and of typical circuit applications.