Caracappa, A. Danneil, C. Fliller, R.P. Padrazo, D. Singh, O. JACoW Geneva, Switzerland 978-3-95450-177-9 10.18429/JACoW-IBIC2016-TUPG37 English 423-426 TUPG37 timing PLC linac operation monitoring Contribution to a conference proceedings 2017 2017-02 http://dx.doi.org/10.18429/JACoW-IBIC2016-TUPG37 http://jacow.org/ibic2016/papers/tupg37.pdf Part of the NSLS-II Personnel Protection System (PPS), the Accumulated Charge Monitor Interlock (ACMI) was developed to ensure the Accelerator Safety Envelope (ASE) limits for charge generation in the NSLS-II Injector are never violated. The ACMI measures the amount of charge in each injection shot using an Integrating Current Transformer (ICT). For logistical reasons, adding a redundant ICT was impractical so in order to achieve the high reliability required for PPS this system is designed to perform self-tests by injecting calibrated charge pulses into a test coil on the ICT and analyzing the returning charge signal. The injector trigger rate is 1.97Hz and self-tests are performed 250 mSec after every trigger pulse. Despite the lack of a redundant charge measurement the ACMI achieved the high reliability rating required for PPS with a mean time between failure (MTBF) rate greater than 10⁶ hours. The ACMI was commissioned in 2014 and has operated to date without any major problems. In 2015 a second ACMI system was commissioned at another location in the injection system.