Description
The Bently Nevada 125768-01 is the Rack Interface Module (RIM) I/O card engineered exclusively for the 3500 Series Machinery Protection System. Installed in Slot 1 of the 3500 rack adjacent to the power supplies, this module provides the physical communication routing interface for configuration, data collection, and diagnostic monitoring. It bridges external configuration software and legacy communications processors with the internal rack backplane.
Commercial Availability & Terms
- Condition: New Original (New Surplus) or Refurbished (fully cleaned and backplane-tested)
- Availability: In stock; typical fulfillment is within 24 to 48 hours
- Warranty: 12-month comprehensive warranty
- Pricing Note: Price depends on market availability and surplus supply metrics. Contact our sales engineering division for an official, firm quote.
Technical Specifications
| Parameter | Value / Specification |
| Manufacturer | Bently Nevada (Baker Hughes) |
| Part Number | 125768-01 |
| Associated Module | 3500/20 Rack Interface Module |
| Serial Communication | RS-232 and RS-422 differential signaling |
| Baud Rate Range | Up to 38.4 kbaud (auto-baud capable) |
| Maximum Cable Length | RS-232: 30 m (100 ft)
RS-422: 1,200 m (4,000 ft) |
| On-Board OK Relay | SPDT type; rated for 5 A @ 24 V DC / 120 V AC max |
| Processor Compatibility | TDXnet, TDIX, DDIX external communications hardware |
| Operating Temperature | −30 to +65 °C (−22 to +149 °F) |
| Storage Temperature | −40 to +85 °C (−40 to +185 °F) |
| Relative Humidity | 95% non-condensing |
Hardware Architecture & Field Routing
The 125768-01 mounts to the rear of the 3500 chassis directly behind the 3500/20 main interface card.
Interface Elements & Switching
- RS-232/RS-422 Slide Switch: A physical hardware switch on the card establishes the electrical standard used by the host configuration port. Ensure this switch matches your cable pinout before inserting the module.
- System OK Relay: This dry-contact relay operates on a “Normally Energized” logic scheme. If the rack drops its internal “OK” state due to a power failure or self-diagnostic error, the relay drops out to trip external alarm annunciators.
- Dedicated Discrete Intputs: Includes dedicated terminations for system resets, alarm channelling, and initiating “Trip Multiply” behavior required during machine startup cycles.
Engineering Constraints & Deployment Practices
Isolation from Critical Protection Path
The 125768-01 does not process machinery shutdown logic or direct sensor voting loops. Because it sits outside the critical safety execution path, you can remove, inspect, or exchange this I/O card while the machinery is operating without dropping the safety interlocks or triggering false machine trips.
Hardware Configuration Lock
The main 3500/20 card utilizes a physical key switch to move between RUN and PROGRAM profiles. When working via the 125768-01 interface to adjust system parameters or upload channel calibration scales, the physical key lock must be turned to the PROGRAM position to unblock the backplane write-protection.
Verification Note: Always confirm the physical switch position for the serial mode (RS-232 vs. RS-422) matches the plant engineering drawings before executing online replacement. Misconfiguration will instantly disable remote SCADA collection paths.
Frequently Asked Questions
Can the 125768-01 be utilized in a Triple Modular Redundant (TMR) rack configuration?
Yes, but the 3500 system architecture requires a dedicated TMR version of the companion front module to run channel comparison. The 125768-01 acts as the downstream termination layer for standard serial connection profiles.
What causes communication connection losses through this card?
In field scenarios, communication drops are typically caused by exceeding the 30-meter design threshold for RS-232 signals, or bad earth grounding on the serial cable shield that allows high levels of EMI to distort the data packets.
Does the 125768-01 support Ethernet or USB connections?
No. The 125768-01 is a legacy serial interface card restricted to RS-232 and RS-422 standards. For modern Ethernet or USB connectivity profiles, the 3500 rack must be upgraded to the newer 3500/22M Transient Data Interface (TDI) module and its corresponding modern I/O footprint.
