Relation Between Electrical and Mechanical Parameters of a Permanent-Magnet Movable-Coil Instrument Having a General Circuit

This is an analysis of the relations between the mechanical parameters and the electrical parameters as measured at the terminals, of a permanent-magnet movable-coil instrument, or other similar electromechanical device, the movable coil of which is free to oscillate, and the circuit of which may consist of any network of resistors which in general may be unknown. It is shown further that by measuring the apparent resistance, inductance and capacitance at the terminals by a special bridge and oscillator and the current per unit deflection, that the values of the undamped period, specific damping coefficient, moment of inertia, and spring stiffness can be computed regardless of the character of the instrument circuit resistor network, or whether it be known or unknown.