[en] A fundamental characteristic of a power pulse due to a reactivity insertion (>$1.00) in a reactor with a large prompt negative temperature coefficient is the minimum period. Normally, the period is determined by plotting appropriately the reactor power versus time, using data from a high-speed chart recorder (e.g., Visicorder). For short periods (∼1 millisecond) a very high-speed recorder is required. A specially designed analog computer can be used to measure this period (or the inverse period) directly from the current produced by a standard power detector. This report describes an analog computer for peak inverse period that has been designed, constructed, and tested. The operation of this device to measure peak inverse periods for typical TRIGA pulses will be described. (author)