Foxboro FBM218 HART Communication Redundant Output Interface Module

External 24VDC power supply not connected or voltage abnormal (below 21.6V or above 26.4V).

Loose power terminal connections, poor contact, or cable open circuit.

Damaged module power interface or internal power circuit failure.

Use a multimeter to check the power input voltage, ensuring it is within the range of 24VDC±5%.

Inspect power terminal block wiring, re-tighten, or replace cables (shielded twisted pair is recommended).

If the power supply is normal but the indicator remains off, attempt to replace the module power interface or contact the manufacturer for maintenance

Voltage fluctuations in the power input (e.g., interference due to poor grounding).

Internal power overload or poor heat dissipation in the module (operating temperature exceeds -20°C~+70°C).

Check if the power grounding meets requirements (independent grounding, grounding resistance <100Ω), and add a voltage stabilizer if necessary.

Clean dust from the module's cooling holes, ensure good ventilation in the installation environment, and avoid high-temperature conditions

Incorrect wiring or disconnection of DeltaV fieldbus (e.g., ControlNet/EtherNet/IP).

Bus terminal resistors not installed or damaged (ControlNet requires 120Ω resistors at both ends).

Module address conflict or communication protocol mismatch with the controller.

Use a multimeter to check the continuity of bus cables and confirm correct polarity (ControlNet requires distinguishing between A/B wires).

Inspect the installation status of terminal resistors and replace damaged ones.

Verify the uniqueness of the module address in DeltaV configuration software, redownload the configuration, and restart the module

HART signal cables not connected as required (250Ω load resistor needs to be connected in parallel).

HART address conflict in intelligent instruments or incorrect setting of communication parameters (e.g., baud rate, parity).

Faulty module HART communication chip or electromagnetic interference.

Check HART loop wiring to ensure correct resistor connection and cable length does not exceed 1500 meters.

Reconfigure the instrument's HART parameters through the DeltaV system or handheld operator (e.g., Rosemount 475).

Add a shielding layer to HART cables and ground them reliably; replace the module if necessary

Abnormal power supply to field instruments (e.g., 24VDC power interruption).

Signal cable open circuit, short circuit, or poor contact (e.g., loose terminal block screws).

Damaged module channel hardware (e.g., ADC converter failure).

Check the instrument's power supply and use a multimeter to measure the voltage at the signal terminal (4-20mA loop should be ≥10VDC).

Inject standard signals (e.g., 4mA, 12mA, 20mA) into the channel input with a signal generator and observe if the module display is normal.

If there is still no response after injecting the signal, try changing the channel configuration in DeltaV configuration; replace the module if ineffective

Signal cables subject to electromagnetic interference (e.g., laid close to power cables).

Zero drift in field instruments or mismatch between range settings and the module.

Gain drift in module channels or improper setting of filtering parameters.

Re-lay signal cables, maintain at least 30cm distance from power cables, and use twisted shielded wires with single-end grounding.

Calibrate the instrument's zero and range (via HART communication or field buttons) to ensure consistency with module configuration.

Adjust the module's filtering time constant in the DeltaV system (e.g., increase from 0.1s to 1s) to reduce noise interference