Product Core Brief
- Model: 125720-01
- Brand: BENTLY
- Series: 3500/32 Relay Output Module Line for 3500 Machinery Protection Racks
- Core Function: Receives rack alarm status signals and drives four isolated DPDT dry-contact relays with configurable AND/OR voting logic for shutdown and alert circuits.
- Product Type: Full-width rack slot relay output I/O module
- Key Specs: 4 independent DPDT relay channels | 30 V DC / 5 A resistive contact rating | Backplane 24 V DC powered
- Condition: New Original (New Surplus)
Product Introduction
The BENTLY 125720-01 is a full-slot relay output module built to translate internal 3500 rack vibration and thrust alarm states into hard-wired external control signals. It delivers isolated dry contacts to actuate shutdown solenoids, horn annunciators, and DCS status inputs.This unit supports custom per-channel voting logic to suppress nuisance trips, cutting unplanned equipment downtime by roughly 75% versus fixed-logic relay alternatives. Its TDXnet backplane bus enables real-time diagnostic reporting to the rack CPU—though your mileage may vary with mixed firmware revision racks.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Module Slot Format | Full-width single slot for standard 3500 rack chassis |
| Backplane Supply Voltage | 18 V DC to 32 V DC nominal 24 V DC rack rail |
| Max Module Power Draw | 6 W at full four-relay energized state |
| Relay Channel Count | 4 fully independent DPDT dry-contact outputs |
| Contact Resistive Load Rating | 5 A at 30 V DC maximum per channel |
| Internal Logic Function | User-programmable AND / OR voting per relay channel |
| Backplane Communication Bus | TDXnet proprietary rack interface |
| Continuous Operating Ambient Temp | -40 °C to +70 °C cabinet air |
| Unit Physical Dimensions | 152 mm × 102 mm × 229 mm (H × W × D) |
| Net Assembly Weight | 0.30 kg unpopulated terminal block |
| Compliance & Safety Standards | API 670 Rev 4, CE EMC Class A, UL 508 listed |
| Built-In Diagnostics | Relay coil fault detection, backplane bus loss monitoring |
Quality Control Process (Engineer’s Perspective)
- Incoming Verification: Cross-reference serial numbers against OEM production logs, scan factory anti-counterfeit QR labels, inspect PCB edge connectors for bent pins, cracked terminal blocks, or discolored relay coils.
- Live Functional Test: Insert the unit into a calibrated 3500 rack, supply nominal 24 V DC backplane power, run a 24 hour cycling test that energizes all four relays every 30 seconds with contact resistance logged hourly.
- Electrical Parameter Test: Run 500 V Megger insulation sweep; pass threshold reads >10 MΩ between relay contact terminals and rack backplane ground.
- Firmware Verification: Read and record module internal firmware revision, cross-check compatibility matrix, photograph terminal screw torque tension consistency.
- Final QC & Packaging: Wipe assembly with anti-static isopropyl wipe, seal inside shielding ESD bag, attach printed QC Passed sticker stamped with exact test completion date.
Replacement Pitfall Guide
❗ Firmware Mismatch: 3500 rack CPU firmware Revision F cannot read extended voting logic parameters on this module. Always upgrade rack CPU cards to Revision G before physical swap.❗ DIP Switch / Jumper Misconfiguration: Factory default voting logic sets all channels to OR logic; critical trip circuits require manual reconfiguration to AND logic to avoid false shutdowns.❗ Terminal / Cable Incompatibility: Do not run AC control wiring adjacent to relay terminal strips; induced noise creates intermittent contact chatter during machine transients.❗ Power Supply Mismatch: Each fully populated 3500 rack with multiple relay modules draws extra DC load; calculate total rack power draw with a mandatory 20% load headroom to avoid backplane voltage droop.❗ ESD Damage: Low-humidity winter cabinet air raises static discharge risk by 3.8x. Place a dedicated anti-static foam mat under the rack before hot-swapping this live backplane module.Keep these in mind and you’ll cut 90% of rework time.
Compatibility Matrix & Benchmarks
Compatibility Matrix
- 125720-01 → All 3500 Series Monitor / CPU / Power Supply Cards : Direct — TDXnet backplane bus match, zero adapter hardware required
- 125720-01 → 3500/30 Analog Output Module : Incompatible — Analog output cards lack relay drive circuitry and voting logic firmware
- 125720-01 → External DIN Rail Relay Termination Blocks : Needs Adaptation — Requires separate interposing relays to reduce contact load below 5 A rating
Benchmarks
- Relay contact resistance (new unit): ≤0.05 Ω per DPDT channel at 25 °C
- Backplane bus scan latency: 2.8 ms full four-channel status refresh
- Terminal screw cycle durability: 1,000 wire insert/remove cycles with no contact resistance shift exceeding 0.10 Ω
