Thursday 27 May 2010

Safe processing of analogue values

The new automation system PSS 4000 from Pilz, now includes safe analogue input modules, which significantly extend the system’s application range. Modular, fine-granular hardware gives the automation system flexibility, enabling the design to be tailored exactly to the requirements of the plant or machine.

The control system PSSuniversal PLC of the automation system PSS 4000 now has various head modules available, to which I/O modules can be connected individually. The head modules are available in different performance classes, either for control functions, for a local preprocessing function or in the form of a pure communication interface for SafetyNET p. All head modules can be used for standard control tasks as well as safety-related control functions up to SIL3 of IEC 61508.

Applications – safe and decentralised
Applications requiring safe, decentralised recording of analogue values are now accessible with the new, failsafe analogue input modules for PSS 4000: due to the redundant input data, a safety assessment in accordance with EN ISO 13849-1 PL e (Cat. 4) and EN/IEC 62061 SIL CL 3 can be achieved.

Two different modules are available for safety-related evaluation of voltage signals from -10 to +10 V or current signals from 0 to 25 mA.

Decentralised, safe recording of analogue values enables the installation work required in widely distributed plants to be reduced, thanks to short cable routes. At the same time, interference on the measuring lines is minimised, shielding measures can be reduced and compliance with installation regulations for control and power cables is much easier.

Analogue modules for extended application range
In addition to the modules for the normal application range, special versions of the module are also available for more extreme application areas. The modules have an identical function, but special measures enable them to be used under heightened environmental conditions – such as in a temperature range of -40 °C to +70 °C. Higher mechanical robustness values for vibration and shock stress also reduce the cost of mechanical compensation measures for items such as mechanical spring or absorption elements. Additional measures for control cabinet air conditioning or dehumidification are no longer needed.

Other potential application areas for safe analogue input modules include monitoring of valve positions, temperature or fill levels on process machinery, or in the field of building automation.

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