The NanoGage Model 100 available from Optra Inc. is an electro-optic short-range position sensor with a 3-mm standoff, low sensitivity to electromagnetic interference and a large-measurement bandwidth. The sensor is suitable for applications such as maintaining a closed-loop position, for automated focusing at a specific surface height, and for run-out and vibration measurements. Its compact cylindrical package facilitates installation. It measures ∼0.5 in. in diameter and 2.2 in. in length, and its structural body is made of aluminum. Linear measurement range is 100 µm, and signal capture range is ±400 µm. Resolution is 15 nm at a 100-kHz measurement bandwidth. The system has an ∼100-µm-diameter laser spot footprint at the target surface.