In its very basic configuration, CROME system is composed of 3 mains devices : the CMPU, the alarm unit (CAU) and the CUPS.
Each device is composed of various electronic boards. The CMPU is the core monitoring and processing unit. It is composed essentially of 3 boards :
- A front end that is composed to collected charges that are generated by the detector. The measurement ranges covers 9 decades without auto-scaling going from the femto-ampere to the micro-ampere. This board can also generate high voltage going from 0 to 2000V.
- The processing boards
- The connection and power supply board
CROME has the ability of measuring very low dose rates down to 50 nSv h−1, whilst being able to measure radiation over a range extending over 9 decades without autoscaling. To reach these performances, the CROME Measurement and Processing Unit (CMPU) is based on the versatile architecture that includes new read-out electronics developed by the Instrumentation and Logistics (IL) section of the RP group coupled with a Zynq reconfigurable System on Chip (SoC) capable of performing complex processing calculations. CROME uses the FPGA section of the SoC for all safety critical functions.
The CMPUs are able to autonomously generate safety output signals that can be routed to physical alarm units and interlock systems. The states of these outputs are determined by the ambient equivalent radiation dose levels and a combination of run time configurable parameters.
The SoC's dual core ARM processors are running an embedded operating system which is used both for communication with REMUS (Radiation and Environment Monitoring Unified Supervision) supervisory system and for data management.
Even if the form factor is different, the CMPU rack version has the same functional bloc as shown before.