Description
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Part Number | 3BDH000031R1 |
| Module Type | Serial Fieldbus Module (Dual Channel) |
| Compatible Base Unit | AC 800F Controllers (PM 802F or PM 803F) |
| Physical Interfaces | Channel 1 & Channel 2 independently configurable (RS232, RS422, RS485 half-duplex) |
| Supported Protocols | Modbus RTU (Master/Slave), Modbus ASCII (Master/Slave) |
| Baud Rate Range | 1,200 bps to 38,400 bps (Configured via Freelance Engineering Tool) |
| Isolation Voltage | 2,500 V galvanic isolation between field interfaces and controller logic |
| Power Supply Input | 5 V DC (±3%) supplied directly through the AC 800F backplane |
| Power Consumption | 1.6 W to 2.6 W (Dependent on communication load) |
| Product Dimensions | 28 mm x 155 mm x 125 mm |
| Net Weight | 0.145 kg |
Product Introduction
The ABB FI820F (part number 3BDH000031R1) is a dual-channel serial communication module engineered for the Freelance Distributed Control System (DCS) platform. Designed to plug directly into AC 800F controller base units (such as the PM 802F or PM 803F), this module expands the processor’s capability to interface with diverse field equipment. It supports three major physical standards—RS232, RS422, and RS485—making it a highly versatile hardware option for integrating third-party PLCs, power meters, gas chromatographs, and variable frequency drives.
Crucial for demanding process automation layouts, the FI820F features robust 2,500 V galvanic isolation on both serial channels. This protects the core AC 800F backplane logic from ground loops, high-voltage surges, and electrical noise typical of remote field installations. By handling Modbus RTU or Modbus ASCII protocol execution at the hardware layer, it guarantees deterministic processor cycles, allowing the main controller to execute high-priority control loops without communication-induced latency.
- FI820F
- FI820F
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No LEDs illuminated on the FI820F faceplate | Controller slot has no 5 V logic power | ❌ Low | Verify the green power/run LEDs are active on the master PM 802F/803F base unit. Make sure the FI820F is firmly locked into the slot. | If the base controller is healthy but the remains dead after reseating, the onboard DC-DC converter on the serial module has failed. Replace the board. |
| Continuous communication timeout alarms in Freelance | Tx/Rx polarity swapped or baud rate mismatch | ✅ High | Check the physical DIP switch settings and program configurations. Use an oscilloscope or line sniffer to verify if Tx signals are generating a response. | Confirm baud rate, parity, stop bits, and station ID match your field device exactly. Correct any swapped RX/TX or A/B wiring. |
| Intermittent data packet errors or CRC failures | Missing end-of-line termination resistors on RS485 link | ✅ High | Measure resistance across the Rx/Tx line pair (A and B lines) with field power isolated. It should read approximately 60Ω (two parallel 120Ω terminators). | Install 120Ω termination resistors at both physical ends of the RS485 daisy-chain network to eliminate signal reflections. |
| Individual field device stops communicating | Field device lost auxiliary power or has damaged transceiver | ❌ Low | Connect a laptop directly to the field device via a local serial adapter and attempt to poll it using standard Modbus testing software. | Do not replace the card. Focus your efforts on repairing or replacing the isolated field transmitter, barrier, or local power supply. |
Frequently Asked Questions (FAQ)
Does the support true online hot-swapping inside an active AC 800F rack?
Yes. The AC 800F controller backplane design and the module support hot-swapping (online replacement). You can extract a failing card and slide in a new one while the controller is powered and running without interrupting the main processor state. However, remember that any active serial loops passing through the card will be temporarily offline until the replacement module initializes and establishes its handshakes.
How do I switch a channel from RS232 mode to RS485 mode?
The physical standard selection is not governed by physical DIP switches on the card itself. Instead, the physical port adaptation and pin assignments are configured dynamically inside the Freelance Engineering Tool, combined with using the correct pinout on your DB9 connection cables. Ensure your cable termination matches the pinout guidelines outlined in the ABB AC 800F hardware manual for your chosen mode.
What is the purpose of the 2,500 V isolation rating on the serial channels?
Industrial environments are prone to high electromagnetic interference and differing ground potentials between the control room and field-mounted devices (which might be over 1,000 meters away). The 2,500 V galvanic isolation on the physically decouples the field wire’s copper paths from the controller’s delicate microprocessors. If a field cable is struck by lightning or shorted to a high-voltage motor frame, the isolation barrier acts as a circuit fuse, sacrificing the communication port to save the main controller.
Can I run both RS232 and RS485 simultaneously on the two different channels?
Yes, absolutely. The two serial channels on the are completely independent. You can run a short-run RS232 link to a nearby local operator panel on Channel 1 while operating a long-distance, multi-drop Modbus network on Channel 2 to collect data from a string of flow meters.
Why choose New Surplus inventory instead of ordering directly from the factory?
The Freelance AC 800F series is a mature platform, meaning ordering legacy components directly through the original factory channels often carries high markups and lead times spanning several weeks. Our New Surplus inventory consists of unused modules in original boxes, stored in climate-controlled environments and ready for immediate shipment. This gets your system back to full hardware redundancy immediately, and we back every card with our comprehensive 1-year replacement warranty.
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