[en] The design of the instrumentation system for the Large Coil Test Facility (LCTF) is described. Sensors are divided into two categories: coil diagnostic sensors, installed in the test coils; and facility sensors, installed in the various systems of the test facility in order to monitor their performance. After signal conditioning, data from the ''fast'' channels are multiplexed, digitized, and stored in four microcomputer systems programmed to be used in a ring buffer mode to record data before and after receipt of a random trigger from the normal zone detection circuitry. ''Slow'' channels are digitized by a scanner and buffered by a microcomputer. Selected data channels are continuously displayed on digital or recorded on strip chart recorders. The microcomputer systems are interfaced to a central minicomputer system for display and archival storage. Facility variables are digitized by a separate scanner system. Certain critical fault variables are compared with set point values, and if they are out of range, cause a programmable logic controller to initiate an emergency coil energy dump. 2 refs