An apparatus includes an elongate body and a sensor. The elongate body has a proximal end and a distal end. The distal end is sized and configured to fit through a naturally occurring orifice of a human body. The sensor is positioned at the distal end of the elongate body. The sensor includes an electrically conductive coil. The coil extends along a longitudinal axis. The coil has a distal terminal winding and a proximal terminal winding. The distal terminal winding extends along a plane that is obliquely oriented relative to the longitudinal axis. The proximal terminal winding extends along a plane that is obliquely oriented relative to the longitudinal axis.
