A New Method for Measurement of Bioelectrical Impedance

The paper describes the theory and practical implementation of a four-electrode method for measuring complex bioimpedance of local tissue. This new method adopts three independent voltages V_in+, V_in-, V_R respectively from the two voltage electrodes and a sample resistor R, which is connected in serial with one of the two voltage electrodes. Theoretical analysis shows that real part Z_real and imaginary part Z_imag of the complex impedance between two voltage electrodes can be acquired from the modular ratios (|V_in+|/|V_R|), (|V_IN-|/|V_R|) and phase difference (_IN+ - _R), (_{IN +} - _R) through simple calculation. The problems with the conventional methods are avoided with this novel technique.