Abstract: A spectrometer for measuring the complex impedance spectrum of tissue comprises: a multi-frequency excitation current generator; a demodulation signal generator; two identical amplification/demodulation circuits; an A/D converter; and a microprocessor for signal processing. In use, the current generator excites the tissue sample and a series-connected reference impedance. The voltages generated in the tissue and reference are measured, demodulated, and digitized in parallel using the demodulation signal generator, the two amplification/demodulation circuits, and the A/D converter. Demodulation is done using the same demodulation signal generated at a frequency with a preset difference from the excitation signal, which allows measurements to be made at a low frequency independent of the excitation frequency. The microprocessor then calculates the complex impedance spectrum in relation to the reference signal.