A compensation circuit has a predetermined, known complex impedance and is located in a handle of a catheter or in a distal end of a cable that connects to the catheter. The compensation circuit is probed with a pilot signal produced by a compensation control. The compensation control measures the complex impedance, which is the combination of the circuit's known impedance as well as that of the cable and then determines the difference between the measured and the known complex impedances which represents that which is attributable to the cable, and is used to cancel out such cable-related contributions to complex impedance in other electrical connections in the same cable. In another aspect, an unknown tissue is identified as one of a plurality of possible tissue types such as regular myocardium, scar and fat based on the measured phase angle of the complex impedance of the unknown tissue.