Multi-electrode impedance sensing

A system, comprising:

• an elongate medical device comprising a shaft and a first electrode and a second electrode disposed on or in the shaft;
• and
• an electronic control unit (ECU) coupled to said elongate medical device and configured to select the first electrode as an electrical source and the second electrode as an electrical sink, to cause an electrical signal to be driven between the source and sink, to detect respective electric potentials on said first electrode and said second electrode while the electrical signal is driven, to determine an impedance respective of one of said first electrode and said second electrode according to the respective electric potentials, to determine the non-binary contact state between the medical device and the tissue based on the determined impedance, and output a signal indicative of the non-binary contact state;
• a display, communicatively coupled to the ECU, and configured to receive the output signal indicative of the non-binary contact state between the medical device and the tissue, and to visualize the non-binary contact state;
• and
• a patch electrode configured to be disposed on the body of a patient, wherein the respective electric potentials are referenced to an electric potential on said patch electrode;
• and
• wherein the non-binary contact state is indicative of a degree of contact between the medical device and the tissue.