CPC A61B 18/1233 (2013.01) [A61B 18/16 (2013.01); A61B 2018/00077 (2013.01); A61B 2018/00083 (2013.01); A61B 2018/00845 (2013.01); A61B 2018/00869 (2013.01); A61B 2018/00875 (2013.01); A61B 2018/00892 (2013.01); A61B 2018/00904 (2013.01); A61B 2018/1286 (2013.01); A61B 2018/167 (2013.01)] | 18 Claims |
1. An apparatus to detect electrical contact between an anatomical tissue portion near a surgical site and a protective shield conductor surrounding an active conductor of an electrosurgical instrument comprising:
a transformer including a primary winding and a secondary winding;
an alternating current (AC) reference frequency signal generator coupled to inject an AC reference frequency signal to the primary winding;
a first reactive impedance coupled in parallel with the secondary winding between a first node and a second node;
wherein the primary and secondary windings are magnetically coupled such that the injected AC reference frequency signal in the primary winding induces an AC reference frequency signal in the secondary winding and the secondary winding is configured to reflect back to the primary winding a reflected AC reference frequency signal having a phase shift relative to the injected AC reference frequency signal that is indicative of an impedance between the first and second nodes; and
a phase match detector circuit is configured to detect a phase match between the AC reference frequency signal and the reflected AC reference frequency signal.
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