AbstractThe design and construction phase for the national spherical torus experiment (NSTX) is under way at the Princeton Plasma Physics Laboratory (PPPL). Operation is scheduled to begin on April 30, 1999. This paper describes the conceptual design for the NSTX central instrumentation and control (I&C) system. Major elements of the central I&C system include the process control system, plasma control system, network system, data acquisition system, and synchronization system to support the NSTX experimental device.