FOXBORO RH926HT

Core Technical Performance Parameters

• Compatible System: Foxboro I/A Series DCS FBM207, FBM208 digital input field modules
• Input Channel Support: 16 isolated digital input channels per module
• Field Input Voltage Range: 18–30 V DC logic ON signal, <5 V DC logic OFF threshold
• Channel Isolation Strength: 500 V AC isolation between channel-to-channel and channel-to-ground
• Response Time: 2 ms typical signal sampling response, software configurable delay filtering
• Overcurrent Protection: Individual channel mini blade fuse per input circuit
• Redundancy Support: Hardware redundant pairing for dual FBM module hot backup
• Operating Temperature: 0 °C to +60 °C continuous cabinet operation
• Humidity Tolerance: 5–95% RH non-condensing
• Mounting Standard: Horizontal DIN rail mounting on DCS standard 200 series baseplate
• Protection Class: IP20 internal cabinet installation only
• EMC Compliance: EN 61000-6-2 industrial immunity standard

Function & Feature Highlights

1. Independent channel fuse protection prevents single field wiring short circuit from damaging entire DCS field bus module
2. Galvanic channel isolation eliminates common-mode voltage interference from long-distance plant field wiring
3. Hardware redundant pairing design supports dual FBM module hot standby for zero downtime process control
4. Per-channel red LED fault indicator to visually identify blown fuse or open field wiring fault
5. Software configurable input signal filtering delay to suppress transient industrial electrical noise false trigger
6. Hardwired module address coding, no manual DIP switch setting required for rapid cabinet deployment
7. Rugged industrial design for continuous 24/7 unattended operation in refinery and power plant DCS control rooms
8. RoHS compliant low-hazard component construction for global industrial plant deployment

Working Principle

1. 24 V DC discrete field signals from process sensors (level switches, pressure limit switches, flame detectors) connect to RH926HT terminal input channels.
2. Each channel passes through independent fuse and isolation optocoupler to convert field voltage signal into digital logic signal.
3. Termination module transmits isolated digital signal to paired FBM field bus module via backplane baseplate bus.
4. If one primary FBM module fails, RH926HT redundant hardware circuit automatically switches signal path to standby FBM module without signal loss.
5. Fuse blown or open field wiring triggers channel LED alarm and transmits fault diagnostic data to DCS central operator station for maintenance alert.

Material & Structural Composition

• Module Housing: Black flame-retardant ABS plastic DIN rail housing
• PCB Substrate: High-temperature FR4 fiberglass circuit board, lead-free solder plating
• Isolation Components: High voltage withstand optocoupler chips
• Protection Components: Fast-acting miniature glass tube fuses per channel
• Terminal Block: Gray plastic screw terminal block, tin-plated copper contact pins
• Baseplate Connection: Gold-plated backplane edge connector for stable bus signal transmission

Installation Requirements

1. Horizontal DIN rail mounting on Foxboro standard 200 series DCS baseplate, vertical installation prohibited
2. Maintain 15 mm horizontal clearance between adjacent modules for heat dissipation
3. Field wiring cable must use shielded twisted pair cable, single-point cabinet grounding of shield layer
4. Module backplane bus connector must fully lock to avoid intermittent signal loss under plant vibration
5. Install inside air-conditioned DCS control room cabinet, ambient temperature controlled below 60 °C

Application Scenarios

• Petrochemical refinery process safety discrete signal monitoring
• Thermal power plant boiler, turbine auxiliary equipment limit signal collection
• Pharmaceutical batch production process interlock discrete signal input
• Oil & gas pipeline compressor station safety alarm signal acquisition
• Chemical plant reactor temperature/pressure interlock switch monitoring

Operation & Maintenance Precautions

1. Replace blown channel fuse only with manufacturer specified ampere rating fuse; higher rating fuse will lose circuit protection function
2. Do not apply AC voltage to DC digital input channels, will permanently damage optocoupler isolation circuit
3. Avoid installation near high-power variable frequency drives to reduce electromagnetic noise interference
4. Conduct quarterly visual inspection of LED fault indicators to detect hidden field wiring open circuit faults
5. Module disassembly and fuse replacement must be performed under DCS system partial power-off state to avoid bus signal crash