MULTIPLE PARAMETER FAULT DETECTION IN ELECTROSURGICAL INSTRUMENT SHIELDS

1 . A method of detecting faults within a shielded electrosurgical instrument, the shielded electrosurgical instrument having an active electrode, the method comprising:

sensing at least two of:

an active voltage in the active electrode;

a current in the active or return electrodes; or

power in the electrosurgical instrument shield;

determining whether a power fault exists, wherein determining whether a power fault exists comprises multiplying the sensed current and the sensed active voltage;

determining at least one of:

(a) whether one or more current faults exists; or

(b) whether a capacitance fault exists; and

altering power delivery to the active electrode if any of the power fault, current faults, or capacitance faults exist.

2 . The method of claim 1 , further comprising determining whether a resistance fault exists, wherein determining whether a resistance fault exists comprises determining whether the expression W shield R trip >V active 2 K scale is true, wherein V active 2 is equal to the mean, squared, active electrode voltage, wherein W shield is equal to the mean, real shield power, wherein R trip is equal to the resistance below which a resistance fault is tripped, and wherein K scale is equal to a scaling constant.

3 . The method of claim 1 , wherein determining whether a current fault exists comprises determining whether the expression I shield 2 >I trip 2 is true, wherein I shield 2 is equal to the mean, squared shield current, and wherein I trip 2 is equal to a constant representing the square of current below which a current fault is tripped.

4 . The method of claim 1 , wherein determining whether a capacitance fault exists comprises determining whether the expression V active 2 >I shield 2 Z fault 2 is true, wherein V active 2 is equal to the mean, squared, active electrode voltage, wherein I shield 2 is equal to the mean, squared, shield current, and wherein Z fault 2 is equal to a constant representing the square of the magnitude of the impedance at which a capacitance fault should be tripped.

5 . The method of claim 1 , wherein determining whether a power fault exists comprises determining whether the expression (W shield >W trip ) is true, where W shield is equal to the mean, real power in the shield and W trip is equal to a constant representing the maximum average value of power above which a power fault may trip.

6 . A system for detecting faults within a shielded electrosurgical instrument, the shielded electrosurgical instrument having an active electrode, the system comprising:

at least one sensor for sensing at least two of:

an active voltage in the active electrode;

a current in the active or return electrodes; or

power in the electrosurgical instrument shield;

a processor configured to determine whether a power fault exists, wherein determining whether a power fault exists comprises multiplying the sensed current and the sensed active voltage, the processor further configured to determine at least one of:

(a) whether one or more current faults exists, or

(b) whether a capacitance fault exists,

the processor further configured to alter power delivery to the active electrode if any of the power fault, current faults, or capacitance faults exist.

7 . The system of claim 6 , wherein the processor is further configured to determine whether a resistance fault exists, wherein determining whether a resistance fault exists comprises determining whether the expression W shield R trip >V active 2 K scale is true, wherein V active 2 is equal to the mean, squared, active electrode voltage, wherein W shield is equal to the mean, real shield power, wherein R trip is equal to the resistance below which a resistance fault is tripped, and wherein K scale is equal to a scaling constant.

8 . The system of claim 6 , wherein determining whether a current fault exists comprises determining whether the expression I shield 2 >I trip 2 is true, wherein I shield 2 is equal to the mean, squared shield current, and wherein I trip 2 is equal to a constant representing the square of current below which a current fault is tripped.

9 . The system of claim 6 , wherein determining whether a capacitance fault exists comprises determining whether the expression V active 2 >I shield 2 Z fault 2 is true, wherein V active 2 is equal to the mean, squared, active electrode voltage, wherein I shield 2 is equal to the mean, squared, shield current, and wherein Z fault 2 is equal to a constant representing the square of the magnitude of the impedance at which a capacitance fault should be tripped.

10 . The system of claim 6 , wherein determining whether a power fault exists comprises determining whether the expression (Wshield>Wtrip) is true, where Wshield is equal to the mean, real power in the shield and Wtrip is equal to a constant representing the maximum average value of power above which a power fault may trip.