A system includes a frame having multiple separate supports and multiple flexible rails. Each support is configured to be secured in a position apart from another support, and each flexible rail is configured to be coupled to the supports and placed under tension. The system also includes a sensor head configured to be mounted on the rails and to move back and forth along the rails. The sensor head is substantially self-contained and configured to receive operating power over the rails. The frame may further include a tensioned member configured to be coupled to the supports, and the sensor head can be configured to move back and forth using the tensioned member. The sensor head can be self-contained in that the sensor head does not push and pull any wiring assembly during movement along the rails.