Power supply and physical layer diagnostics on the bus
R. STAHL’s new Advanced Fieldbus Power Supply (A-FPS) is the first and only power supply module for FOUNDATION™ fieldbus H1 segments to additionally provide a wide range of physical layer diagnosis functions. At a mere 10% premium over the standard supply module from the same series, the integrated devices enable complete and continuous plant monitoring. In the past, the integration into asset management systems required separate, cost-intensive diagnosis modules and software tools. Each Advanced Fieldbus Power Supply (A-FPS) not only detects overload and short circuits on its segments, but also continuously registers the physical parameters of the fieldbus, such as voltage and current on the trunk, communication level, noise level, asymmetries and jitter.
Error messages can be routed to a management software via the Diagnosis Communication Module (DCM) and the FF H1. Additionally, they are signalled via a potential-free relay contact. A serial interface on the front side makes it possible to read out detailed data on site by means of standard terminal programs. Lastly, colour LEDs in a traffic light design following the NAMUR NE107 scheme ensure that untrained staff members can identify problems at the module at first glance. In case of deteriorating transfer quality on the bus, warning messages can be triggered proactively, allowing users to make adjustments before a segment fails. The line quality threshold value can be manually adjusted by means of a control dial at the module. The compact units can be installed on a DIN rail or on a bus-Carrier which houses modules for up to eight standard-supply segments or four segments with a redundant supply. The carrier systems are also available as adapted, easy-to-handle models for specific host systems and their plug connectors, such as Emerson Delta V and Yokogawa Centum VP (upcoming models will be suitable for Honeywell and Invensys controllers). Each power supply module features an integrated terminating resistor which can be turned off in host systems with their own bus terminator. Just like the basic version, the Advanced Fieldbus Power Supply System supplies the fieldbus with 28 V and 500 mA and enables a 1 A supply via a parallel connection of two devices in “Boost” mode. If users decide on a redundant supply setup in which two modules provide 250 mA each, they will automatically also benefit from redundant diagnosis functions.