MEASUREMENT METHODS
Voltage output from the tissue was amplified using a Wheatstone Bridge circuit and a differential amplifier. Multiplication of this signal with the in-phase and out-of-phase versions of the sinusoidal, followed by low pass filtering produces the outputs from the circuit, Y and Z, which are proportional to the magnitudes of the resistive and reactive components of the body impedance. Patient isolation was again provided by the use of optically coupled amplifiers on the measurement side.