Frequency-response analysis and parameter measurement of a d.c.-excited drag-cup tachogenerator

An analysis is presented which shows how the electrical time constant of the rotor of a drag-cup tachogenerator gives rise to nonlinear characteristics with respect to mean speed and the frequency of speed variation, when used with d.c. excitation as an accelerometer. Simple and accurate methods for the measurement of the rotor time constant and for the calibration of the accelerometer are described.