The CL-2400, a noncontact thickness measuring system offered by Ono Sokki Technology Inc., is for conductive and semiconductive materials. It calculates the thickness from gap capacitance, a method that the company says provides high accuracy and stability and that is immune to magnetic fields and ambient light. Built-in self-calibrating software requires calibration only every three years, and a large seven-segment LED display provides easy reading. The system can measure thicknesses of up to 4 in. with submicron accuracy and is supplied with RS-232C output for interfacing to a PC or data acquisition system. Response speed for in-line applications is 20 ms.