Sealing and/or cutting instrument

A surgical instrument, comprising:

• a first arm having a first proximal end and a first distal end, the first distal end spaced from the first proximal end in a distal direction;
• a second arm having a second proximal end and a second distal end, the second distal end spaced from the second proximal end in the distal direction, the second arm having a surface that faces the first arm, and the second arm physically coupled to the first arm such that the first arm and the second arm are movable toward one another;
• a ferromagnetic heater forming a rigid loop, the rigid loop physically coupled to and extending from the first arm in the distal direction;
• and
• a sensor physically coupled to the surface of the second arm at a position distal of the first distal end with respect to the distal direction and aligned with the rigid loop with respect to a direction perpendicular to the distal direction, wherein the sensor monitors at least one property of tissue positioned between the ferromagnetic heater and the sensor.