Bently Nevada 3500/25 (125800-01) Keyphasor Module – Stable Phase Reference and Speed Input for the 3500 System

The Bently Nevada 3500/25 Keyphasor Module, model 3500/25 with part number 125800-01, provides a precise once-per-turn phase reference to the 3500 rack. It’s the piece that lets your machinery protection system synchronize vibration data with actual shaft position—critical for 1X diagnostics, balancing, vector plots, and reliable speed tracking.

In many cases, plants pair it with 3300 XL proximity transducers or a magnetic pickup to generate clean reference pulses. From my experience, it’s a go?to choice on turbines, compressors, and high?speed trains where phase certainty matters as much as the amplitude.

• Accurate once-per-turn reference – Generates the Keyphasor signal used for phase-based vibration analysis and balancing.

• Dual-channel capability – Typically supports up to two independent Keyphasor inputs for multi-marker or redundant pickup strategies.

• Sensor flexibility – Accepts proximity probe systems (e.g., 3300 XL 5 mm/8 mm) or a magnetic pickup, depending on your machine design.

• Integrated with 3500 rack – Provides conditioned reference pulses to all relevant monitors over the backplane; no external power or network box needed.

• Service-friendly diagnostics – Buffered/logic outputs available on the rear I/O module (varies by option) to scope the signal during commissioning.

• Status and OK monitoring – Channel health and module status tie into 3500 system events, so issues are visible immediately.

• Software configurable – Configure speed range, pulse polarity, and related parameters through standard 3500 configuration tools.

You’ll typically find the 3500/25 on rotating assets where phase coherence is essential:

• Gas and steam turbines – phase reference for 1X amplitude/phase, startup coastdown profiles, and speed tracking.

• Centrifugal and axial compressors – stable reference for vector plots and unbalance diagnostics.

• Large motors, generators, and fans – balancing work and cross-channel phase analysis.

• Gearboxes – phase-marked vibration for gear mesh investigations and runout compensation.

• Reliability – Proven architecture within the widely deployed 3500 platform; seems to be the standard in many critical services.

• Compatibility – Works with common Bently Nevada proximity systems and magnetic pickups, so you can reuse existing sensors in most cases.

• Efficiency – Dual-channel capability can reduce slot count and simplify wiring versus separate single-channel cards.

• Lifecycle support – Documentation, spares, and configuration tools are consistent across the 3500 family, which helps maintenance teams.

• Signal integrity – Clean triggering improves the quality of phase-based diagnostics, often resulting in faster, more confident fault identification.

• Rack and cabinet – Install in a certified 3500 rack within a clean, ventilated enclosure. Keep ambient conditions within the 3500 system spec.

• Wiring practices – Use shielded, twisted-pair cabling for proximity/magnetic pickups; ground shields at one end only. Route away from VFD and high-current lines.

• Probe setup – Set correct probe gap and align the Keyphasor target to ensure a crisp, once-per-turn pulse. Verify with the I/O buffered output on a scope.

• Safety – De-energize the rack before inserting/removing modules. Observe ESD precautions. For hazardous areas, follow the approved installation drawings.

• Routine checks – Periodically verify pulse stability during runups, inspect connectors/terminal tightness, back up configuration, and document any threshold changes.

• Designed for use within the Bently Nevada 3500 platform and aligned with CE and North American safety marks (UL/cUL, CSA for applicable rack installations).

• Typical manufacturer warranty: 1 year. Extended coverage and service agreements are available in many regions.

If you’re replacing an existing card, please confirm your rack slot position, I/O module option, and sensor type; that detail helps ensure the 3500/25 125800-01 lands plug?and?play with your current configuration.