Patent ID: 8454505

Claim:
An electronic medical device for continuously and simultaneously measuring an impedance signal and a biopotential signal on a biological subject's skin, the device comprising: input and output electrodes provided for being attached to the biological subject's skin and connected to input and output terminals of the device; a current source connected to the output terminals configured to generate a predetermined alternating current having a first frequency above a predetermined minimum frequency, the predetermined alternating current being applied to the output electrodes for creating an alternating voltage signal over the input electrodes; an impedance signal extraction module connected to the input terminals and configured to extract the alternating voltage signal from an input signal which is measured on the input electrodes and to determine the impedance signal from the alternating voltage signal, the impedance signal extraction module comprising a first amplifier connected to the input terminals and configured to amplify the input signal and a demodulation module connected to the first amplifier and configured to demodulate the input signal using a control signal having a frequency equal to the first frequency; and a biopotential signal extraction module connected to the input terminals and configured to extract the biopotential signal from the input signal, wherein the demodulation module comprises first and second demodulation modules using two control signals having a frequency equal to the first frequency but 90° phase shifted with respect to each other, the first and second demodulation modules being configured to extract in parallel a first and a second baseband voltage signal representative of real and imaginary components of the impedance signal.