This article describes a user‐controlled detector simulator to aid development of the grazing incidence spectrometer (GIS), which forms part of the coronal diagnostic spectrometer on‐board the solar and heliospheric observatory. The simulator was a vital element in carrying out full range tests of the GIS processing electronics in the absence of real detectors, including extreme conditions not easily achievable by other means. With a large degree of flexibility, the simulator provides a wide range of characteristics of output events of realistic shapes. Although the simulator was designed specifically to simulate the spiral anode as used by the GIS, the design is applicable to any three channel detector system and has since been used for theFONEMAinstrument for the Russian Mars96 mission. The simulator functionality, performance parameters, software and hardware design, and the overall grounding scheme are presented. The simulator performance with some test results are also discussed. ©1996 American Institute of Physics.