Patent ID: 8836345

Claim:
An apparatus for use in performing impedance measurements on a subject, wherein the apparatus includes a processing system for: a) causing a first signal to be applied to the subject, the first signal being voltage drive signals to be applied to the subject via first electrodes b) determining sensed current signals caused by the voltage drive signals; c) determining an indication of a second signal measured across the subject, the indication of the second signal being a body centre voltage derived from sensed voltages measured via respective second electrodes; d) using the indication of the second signal to determine if an unacceptable imbalance exists; and, e) if an unacceptable imbalance exists: i) determining a modified first signal in accordance with the imbalance by: determining upper and lower impedances for the subject using the sensed current signals, the voltage drive signals, and the body centre voltage; and determining modified voltage drive signals using the upper and lower impedances and an ideal current signal indication; and, ii) causing the modified first signal to be applied to the subject to thereby allow at least one impedance measurement to be performed.