An automatic transfer function measuring and recording system

IN making frequency response tests of various devices, the phase and amplitude of the output must be measured when a signal having a known phase and amplitude is applied to the input. These data may be recorded in the form of a polar, or Nyquist, plot of amplitude with phase, frequency being varied as the parameter. If the input is set as the reference corresponding to a unit vector with its tip at the point (1,0) on the polar plot, then the locus of the vector representing the output of the device on the same polar plot will be the transfer function of the device throughout the range of frequencies being tested.