Digital impedance measurement based on inverse sine function module

A digital method for the measurement of the real and imaginary parts of the impedance is described. The method depends on generating three analog signals. The first is proportional to the voltage (V_z) across the unknown impedance; the second is proportional to the current (I_z) through it, and the third is proportional to the phase (θ) between them. These three analog signals are then applied to a simple hybrid circuit that gives digital numbers that are proportional to (V_z/I_z)(sin θ) and (V_z/I_z)(cos θ), which are equal to the imaginary and the real part of the impedance.