Yokogawa AFG20D Duplexed Field Control Unit

Configured for duplexed control processing and remote input/output (RIO) routing in CENTUM VP platforms, the Yokogawa AFG20D (AFG20D Duplexed Field Control Unit) provides direct physical/electrical execution.

Hardware Specifications

Process Control and DCS Instrumentation

• 4-20 mA HART Loop Protocol Integration: The duplexed control architecture manages real-time process loops by executing synchronous scanning cycles that route 4-20 mA analog inputs and high-frequency HART digital diagnostic data directly into the 32 Mbyte memory map. This allows active instrument monitoring without processing latency.
• Galvanic and Channel-to-Channel Isolation: The internal communication backplane uses advanced dielectric isolation pathways to isolate individual I/O channels. This channel-to-channel isolation protects the main processor unit from field-side loop surges and potential ground loop interference across the remote I/O layout.

Frequently Asked Questions

Q: What is the main advantage of the AFG20D over standard field control units?

A: The AFG20D features an enhanced processor module containing 32 Mbyte of main memory (double the capacity of standard 16 Mbyte models), allowing it to handle larger RIO databases, more complex control logic loops, and more extensive system communication tables.

Q: How is memory protected on the AFG20D during a total power failure?

A: The AFG20D relies on an integrated battery backup system to preserve volatile RAM data. Upon power loss, the backup system maintains memory contents for up to 72 hours, requiring at least 48 hours of live operational recharging to reach full capacity.

Field Installation Guidelines

• Cabinet Earthing and Noise Abatement: Connect the cabinet's integrated copper grounding plate directly to the plant instrument ground bus. Ensure a solid, low-resistance connection (less than 1.0 Ohm) to protect the sensitive internal backplanes and guarantee noise-free communication for the 4-20 mA HART loops.
• Thermal Management and Heat Dissipation: Ensure the cabinet's internal cooling vents are completely unobstructed. The module dissipates a rated heating value of 230 W (828 x 10^3 J/h); maintaining clear airflow paths is necessary to prevent thermal stress within the enclosure during continuous duplex operation.
• Power Cable Isolation: Run AC utility power supply lines (100-120 VAC or 220-240 VAC) in separate steel conduits from the low-voltage DC communication and instrument signal cables. This physical segregation prevents high-voltage inductive coupling from corrupting the internal high-speed RIO bus.