A four-electrode low frequency impedance spectroscopy measurement system using the AD5933 measurement chip

This paper presents the design of a four electrode impedance measurement circuit dedicated to bioimpedance embedded applications. It extends the use of the AD5933 measurement chip to allow it to operate in a four electrode configuration in order to limit the effects of the parasitic impedances between the medium under test and the electrodes. The circuit has shown a good measurement accuracy on various test circuits. In association with a four microband electrode system it has been successfully used to characterize small physiological samples (50 mu l) with conductivities ranging from 0.14 to 1.2 S m(-1). It can be used as an alternative bioimpedance measurement approach for embedded applications operating in the four electrode configuration.