A method and apparatus for displaying complex impedance and related physical characteristics of an object (30) at a plu- rality of sinusoidal frequencies over a wide frequency range. Excitation signal waveforms (10, 14, 18) are stored in digital form. Digital sampling and processing circuitry (84, 86) provide high form. Digita l sampling and processing circuitry (84, 86) provide high noise immunity and accurate measurement at all impedance phase angles. The technique is particularly well-suited to the measurement of complex impedances in living biological tissue because the digital implementation results in highly accurate mea- surement values over a plurality of selectable frequencies within a wide sinusoidal frequency region. A novel adaptation of digital cross-correlation (84) and convolution (86) techniques is used to simultaneously display (72) real and imaginary electrical imped- ance of living biological tissue at several selectable sinusoidal frequencie s.
METHOD AND APPARATUS FOR DISPLAYING MULTI-FREQUENCY BIO-IMPEDANCE