System for measuring impedance between a plurality of electrodes of a medical device

Abstract

The present disclosure is directed to measuring impedance across a plurality of electrode pairs. The disclosed systems and methods may simultaneously provide drive signals between electrode pairs and then sense the voltage signals that develop at the electrodes. Digital signal processing may be used to synchronously demodulate the voltage signal at each electrode to determine impedances at the electrodes. Each electrode pair may be driven at a unique frequency to allow for significantly increasing a number of electrode pairs and/or increasing drive current magnitudes. Synchronous demodulation allows the unique frequencies to be detected independent of each other while minimizing crosstalk. Typically, the drive frequencies are made orthogonal by setting the drive frequencies at harmonics of a common base frequency and measuring a response over an integer number of cycles. In an embodiment, quadrature demodulation may occur providing a real component for resistive impedance and an imaginary component for reactive impedance.