Standards-Based Open-Source PLC Diagnostics Monitoring

PLCs are widely used to control and monitor industrial processes at CERN. Since these PLCs fulfill critical functions, they must be placed under permanent monitoring. However, due to their proprietary architecture, it is difficult to both monitor the status of these PLCs using vendor-provided software packages and integrate the resulting data with the CERN accelerator infrastructure, which itself relies on CERN-specific protocols. This paper describes the architecture of a stand-alone "PLC diagnostics monitoring" Linux daemon which provides live diagnostics information through standard means and protocols (file logging, CERN protocols, Java Monitoring Extensions). This information is currently consumed by the supervision software which is used by the standby service to monitor the status of critical industrial applications in the LHC and by the monitoring console used by the LHC operators. Both applications are intensively used to monitor and diagnose critical PLC hardware running all over CERN.