A technique for measuring and selectively adjusting a clearance between a stationary object and desirably a rotating object includes a non-contact, sensing system having a sensor attachable to the stationary object, a mask having a predetermined sized viewport or aperture that sets or limits the sensing or operation of the sensor, and a controller. The sensor is operable for sensing within a field of view a portion of the rotating object and generating a signal in response thereto. The field of view varies in response to varying the clearance between the sensor and the second object. Desirably, the portion of the second object includes a varying pattern. The controller is operable to determine the clearance between the first object and the second object in response to the signal. In another embodiment, sensing system is operable to adjust the clearance by controller providing an electrical current to a resistive heating element in the thermally expandable portion of a plurality of segmented labyrinth seals. The sensing system is also operable to measure vibration of the rotating object.