An apparatus includes a shaft assembly, an end effector, and a sensor. The shaft assembly defines a longitudinal axis. The end effector is positioned at a distal end of the shaft assembly. A portion of the end effector is offset from the longitudinal axis. The sensor is configured to generate a signal in response to a magnetic field. The signal is configured to indicate a position of the end effector within three-dimensional space. The sensor is coaxially positioned about the longitudinal axis.