Brand: Bently Nevada

3500/25 Keyphasor® Module

Name: Bently Nevada 3500/25 Keyphasor Module – Datasheet & Quote
Brand: Bently Nevada

Description

Overview

The Bently Nevada 3500/25 Keyphasor® Module provides the precise once-per-revolution phase and speed reference that unlocks advanced diagnostics in a Bently Nevada 3500 rack. By conditioning proximity-probe or magnetic-pickup tach signals into a clean Keyphasor reference, the 3500/25 enables order tracking, orbit/polar plots, startup/coast-down analysis, and accurate correlation of alarms across the rack—without interfering with protection logic. Deployed alongside vibration monitors such as 3500/40M (Proximitor) or 3500/42M (Velocity/Accel), and streamed via a 3500/22M TDI to System 1, the Keyphasor module turns raw vibration into actionable, phase-aware insight for compressors, turbines, large motors/generators, pumps and fans.

Why a Keyphasor Matters

A machinery protection rack can alarm on overall levels, but fault identification (unbalance, misalignment, rubs, looseness, fluid-induced instabilities, blade-pass, gear mesh) often requires knowing phase vs. speed. The 3500/25 Keyphasor Module delivers a stable one-per-rev (or scaled) reference so you can:

Track phase angle of shaft vibration, create orbits and polar plots, and separate synchronous from asynchronous content.
Run order-based diagnostics during startups, coast-downs and variable-speed operation.
Align alarms and events from multiple monitors in time and rotational position for fast root-cause analysis.

How the 3500/25 Works

Inputs & Transducers: Accepts eddy-current proximity (tach) or magnetic pickup signals. Each input is validated, shaped and converted to a Keyphasor pulse train.
Dual Independent Channels: Two channels can be configured redundant (two sensors on one machine), diverse (two different machines), or gear-scaled (tooth count) for multi-target applications.
Scaling & Validation: Supports once-per-rev (keyway/notch) or gear-ratio scaling to derive true RPM. Signal validation maintains clean triggering across low and high speeds.
Rack Integration: The Keyphasor reference is distributed to other 3500 monitors for protection and to System 1 (via 3500/22M TDI) for trends, waveforms, orbits and order plots. Protection remains in the monitors; the 3500/25 supplies the reference only.

Integration with System 1 (Data & Diagnostics)

When your rack includes a 3500/22M TDI, the 3500/25 provides synchronized phase/speed data so System 1 can store phase-referenced waveforms, build Bode/Cascade/Waterfall plots, and correlate temperature, process and vibration events by rotational position. This gives maintenance teams higher confidence during balancing, alignment checks, and post-trip investigations.

Typical Channel Architectures

Single Train (Redundant Tach): CH-A once-per-rev proximity on keyway; CH-B magnetic pickup on gear tooth—redundancy plus cross-validation.
Twin-Train Machine: CH-A on Compressor-1; CH-B on Compressor-2—single module serving two shafts.
High-Tooth Gears: Gear with N teeth; configure pulses/rev to 1 using scaling so monitors and System 1 see accurate RPM.
Keyphasor + Keyphasor (Dual Bearings): Use two once-per-rev targets for complex trains needing multiple phase references.

Setup & Configuration Checklist (Practical)

Transducer data: type (prox/mpu), gap, sensitivity, cable length.
Targeting method: once-per-rev notch/keyway or gear tooth count (N).
Speed range: min/max RPM for reliable triggering and anti-bounce filtering.
Channel use: redundant vs. separate machines; assign scaling per channel.
Rack map: confirm slot, monitor dependencies (e.g., 40M/42M), and System 1/TDI versions.
Validation: live check RPM stability vs. DCS/PLC tach; verify phase coherence with radial probes.

Applications & Fault Coverage

Turbomachinery: gas/steam turbines, expanders—order plots, Bode during run-ups; phase-based rub/misalignment detection.
Compressors & Blowers: unbalance, looseness, aerodynamic instabilities, surge event timing.
Large Motors/Generators: soft-foot/misalignment identification with phase tracking.
Pumps/Fans: phase-referenced trend correlation for cavitation/rub.

Commissioning & Maintenance Best Practices

Place the once-per-rev mark at a clear mechanical reference (keyway or precision notch).
For gears, document exact tooth count and desired pulses/rev; apply gear scaling accordingly.
Route tach leads away from high-noise power cabling; check grounding/shielding.
After configuration, run a startup test: verify stable RPM, correct phase lock, and expected order amplitudes in System 1.
Keep a spare 3500/25 for fleets where run-up data are critical to outage planning.

Compatibility & Ordering Notes

Share your transducer type/model, gap and cable length, tooth count or notch details, machine speed range, rack BOM/slot map, and System 1/TDI versions. We’ll confirm firmware compatibility, channel assignments, and the right scaling so your 3500/25 Keyphasor Module delivers a clean, reliable reference across the rack.

Included / Not Included

Included: 3500/25 Keyphasor® Module (card only).

Not included: transducers, I/O modules, rack hardware, cables—quoted as required.

Technical Specifications

Parameter	Value
Manufacturer	Bently Nevada
Model	3500/25 Keyphasor® Module
Function	Once-per-revolution phase and speed reference for the 3500 rack
Inputs	Eddy-current proximity (tach) or magnetic pickup signals
Channels	Two independent channels (redundant, diverse or gear-scaled)
Scaling	Once-per-rev (keyway/notch) or gear-ratio scaling
Integration	Distributes reference to 3500 monitors and to System 1 via 3500/22M TDI
Power consumption	3.2 W typical
Input signal range	+0.8 V to -21.0 V (non-isolated I/O modules); +5 V to -11 V (isolated I/O modules)
Input impedance	21.8 kΩ minimum
Speed/frequency input range	1 to 1,200,000 cpm (0.017 Hz to 20 kHz)
Speed/frequency output range	1 to 99,999 cpm (0.017 to 1667 Hz)
Passive magnetic pickup minimum speed	Greater than 200 rpm (3.3 Hz)
Auto threshold	Minimum signal 2 V peak to peak, minimum frequency 120 rpm (2 Hz)
Manual threshold / hysteresis	User-selectable 0 to -20 Vdc, minimum signal 500 mV peak to peak / hysteresis 0.2 to 2.5 V
Buffered outputs	Two at front (coaxial) and two at rear (Euro Style connectors); 504 Ω maximum output impedance
Keyphasor transducer power supply	-24 Vdc, 40 mA maximum per channel
Operating temperature	-30 °C to +65 °C (0 °C to +65 °C with Internal Barrier I/O Module)
Storage temperature / humidity	-40 °C to +85 °C / 95%, non-condensing
Main module dimensions (H x W x D) / weight	119.9 mm × 24.4 mm × 256.5 mm / 0.34 kg (0.76 lb)
I/O module dimensions (H x W x D) / weight	241.3 mm × 24.4 mm × 103.1 mm / 0.46 kg (1.01 lb)

3500/25 Ordering Information and Part Numbers

The Enhanced Keyphasor Module is ordered as 3500/25-AA-BB-CC. Field A is the channel count: 01 supplies a single half-height 2-channel Keyphasor card and 02 supplies two half-height 2-channel cards for four channels. Field B is the I/O module: 01 Internal Terminations, 02 External Terminations, 03 Internal Barrier I/O with Internal Terminations, 04 Isolated I/O with Internal Terminations and 05 Isolated I/O with External Terminations, the last two being intended for magnetic pickups. Field C is the agency approval: 00 not required, 01 cNRTLus (Class 1, Div 2), 02 ATEX/IECEx/CSA (Class 1 Zone 2).

The spare main card is 149369-01 (Enhanced Keyphasor Module), which Bently Nevada lists as a direct plug-in replacement for the earlier Keyphasor Module 125792-01. Rear modules are 125800-01 (Keyphasor I/O Module, Internal Terminations), 126648-01 (External Terminations), 125800-02 (Isolated Keyphasor I/O Module, Internal Terminations), 126648-02 (Isolated Keyphasor I/O Module, External Terminations) and 135473-01 (Keyphasor I/O Module with Internal Barriers and Internal Terminations). Connector headers are 00580438 (4-position, green) and 00502133 (12-position, blue); the user guide is document 129770.

For external-termination builds, the termination block and cable are separate line items: 128718-01 is the Keyphasor External Termination Block with Euro Style Connectors and 128726-01 is the version with Terminal Strip Connectors. The signal cable is 129530-AAAA-BB, with lengths of 0005, 0007, 0010, 0025, 0050 or 0100 feet and BB set to 01 (not assembled) or 02 (assembled). Half-height mounting hardware is also listed: 125388-01 Half-height Chassis, 125565-01 Card Guide, 04300111 assembly screws and 131151-01 Half-height Blank Front Panel Cover.

3500/25 Rack Capacity, Redundancy and Isolated I/O Notes

A 3500 rack accepts up to four Keyphasor signals in a normal configuration and up to eight in a paired configuration, provided there are no more than four primary inputs. A paired arrangement needs two consecutive monitoring positions; four modules then take four primary and four backup inputs and deliver four outputs, one per module. For Triple Modular Redundant systems that need a Keyphasor input, two modules are used in parallel to give the rest of the rack a primary and a secondary signal. The half-height card needs a mounting adapter to sit in a full-height slot.

The isolated I/O modules were created for magnetic pickup installations where the Keyphasor signal is wired in parallel to other equipment such as a control system. They also work with Proximitor sensors, but only when an external power supply is provided. Their main purpose is shaft speed rather than phase: they add slightly more phase shift than the non-isolated versions. Speed accuracy for non-processed signals is ±1 cpm from 0.017 to 100 Hz, ±8 cpm from 101 to 500 Hz and ±1% of cpm from 501 Hz to 20 kHz.

Other Models in the Bently Nevada 3500 Machinery Protection System Range

Seven Star LLC supplies models from the Bently Nevada 3500 Machinery Protection System range in Oman and the GCC. Compare the related models below and request a quote for the one that matches your application.

Model	Category
Bently Nevada 3500 Machinery Protection System	Vibration Monitoring	View details
3500/15 AC/DC Power Supply Module	Vibration Monitoring	View details
3500/25 Keyphasor® Module	Vibration Monitoring	You are viewing this model
3500/22M Transient Data Interface (TDI)	Vibration Monitoring	View details
Bently Nevada 3500/33 16-Channel Failsafe Relay Output Module – 149992-02	Vibration Monitoring	View details
Bently Nevada 3500/32M 4-Channel Relay Module	Vibration Monitoring	View details
3500/40M Proximitor® Monitor	Vibration Monitoring	View details
Bently Nevada 3500/42M Proximitor Seismic Monitor	Vibration Monitoring	View details
Bently Nevada 3500/45 Position I/O Module – 135137-01	Vibration Monitoring	View details
Bently Nevada 3500/50 Tachometer Module	Vibration Monitoring	View details
3500/60 Temperature Monitor	Vibration Monitoring	View details
Bently Nevada 3500/60-01-00 Temperature Monitor Module	Vibration Monitoring	View details

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About brand

Bently Nevada is the American machinery protection and condition monitoring brand behind the 3500 rack, the 3300 XL proximity probe and the System 1 software. It was founded in 1961 in Minden, Nevada, and is today a Baker Hughes business.

Seven Star LLC is an independent supplier in Muscat. We list Bently Nevada monitors, I/O modules, probes, proximitors, velocity transducers and transmitters for rotating equipment in Oman and the GCC, and source them by full part number.

Bently Nevada company profile

Established	1961, Minden, Nevada, USA, by Donald E. Bently. The business started earlier as Bently Scientific in Berkeley, California (1956).
Known for	The first commercial eddy-current proximity transducers for measuring shaft vibration and position on high-speed turbomachinery
Ownership	Acquired by GE Energy in 2002; part of Baker Hughes since GE Oil & Gas combined with Baker Hughes in 2017
Rack generations	5000 series (from 1965), 3300 series (from 1988), 3500 series (from 1995), Orbit 60 (current platform)
Product families	Machinery protection racks, proximity probes and proximitors, Keyphasor sensors, velocity and acceleration transducers, 2-wire vibration transmitters, general-purpose monitors, portable analyzers, wireless sensors and System 1 condition monitoring software
Typical machines	Steam and gas turbines, centrifugal and reciprocating compressors, pumps, motors, generators, fans and gearboxes

Milestones

1956: Donald E. Bently starts Bently Scientific in Berkeley, California.
1961: The company moves to Minden, Nevada, as Bently Nevada.
1965: The 5000 series monitoring system is introduced.
1988: The 3300 series follows.
1995: The 3500 machinery protection system is launched.
2002 and 2017: GE Energy acquires Bently Nevada; it becomes part of Baker Hughes in 2017.

Bently Nevada product series

Series	Type	What it does
3500	Machinery protection rack	Continuous online protection with alarm and danger relays. Modules include the 3500/15 power supply, 3500/20 rack interface, 3500/25 Keyphasor, 3500/42M proximitor/seismic, 3500/50 tachometer, 3500/60 temperature, 3500/33 relay and 3500/92 communication gateway
3500 recip modules	Reciprocating compressor monitoring	3500/70M impulse velocity, 3500/72M rod position and 3500/77M cylinder pressure
Orbit 60	Protection and monitoring platform	The current Bently Nevada platform for protection, condition monitoring and data integration with System 1
3300 XL 8 mm	Proximity transducer system	Probe, extension cable and proximitor sensor for radial vibration, thrust position and Keyphasor reference on fluid-film bearing machines; also 5 mm and 25 mm versions
330500 Velomitor, 190501 Velomitor CT	Piezo-velocity sensors	Casing velocity on rolling-element bearing machines and low-speed cooling tower fans
990 and 991	2-wire transmitters	4-20 mA vibration (990) and thrust position (991) signals straight into a PLC or DCS, without a monitor rack
1900/65A, 2300	Compact monitors	Protection for balance-of-plant pumps, fans and motors where a full 3500 rack is not justified

A proximity probe measures the gap to the shaft, so it sees shaft movement inside a fluid-film bearing directly. A velocity or acceleration sensor sits on the casing and suits rolling-element bearing machines. Critical turbomachinery usually carries two X-Y probes per bearing, two axial probes for thrust position and a Keyphasor probe for speed and phase.

Where Bently Nevada systems are used

In Oman and the GCC, Bently Nevada racks and probes protect gas turbines, compressors and steam turbines in gas processing, LNG, refining, petrochemical, power and desalination plants. Many installations are 3500 racks that have run for years, so most requests are for like-for-like module, probe, extension cable and proximitor replacements, plus upgrades to newer monitors.

Ordering and replacement: what we need

For probes and proximitors, send the full part number with all option digits (for example 330101-00-27-10-02-05). The digits set the probe length, cable length, connector and approvals, and the probe, cable and proximitor must match in total system length. For 3500 modules, send the module and I/O part numbers from the rack and say whether the I/O is internal or external termination, or barrier type. If a module is obsolete, we quote the replacement that Bently Nevada names and point out any configuration or firmware change.

Facts checked against Baker Hughes Bently Nevada pages and published company history, October 2026.

Browse Bently Nevada products by category: Vibration.

FAQ

Questions about the 3500/25 Keyphasor® Module

Answers from our engineering team on installation, compatibility and integration.

01What does the Bently Nevada 3500/25 Keyphasor Module do in a protection rack?

It conditions proximity-probe or magnetic-pickup tach signals into a clean once-per-revolution Keyphasor reference, enabling phase- and speed-based diagnostics such as orbits, polar plots, and order tracking without interfering with the protection logic running in monitors like the 3500/40M or 3500/42M.

02What types of speed/phase transducers does the 3500/25 accept?

It accepts both eddy-current proximity (tach) probes and magnetic pickup (MPU) signals, validating and shaping each into a usable Keyphasor pulse train.

03Can a single 3500/25 module serve two separate machines?

Yes — its two independent channels can be configured as redundant (two sensors on one machine), diverse (one channel per separate machine), or gear-scaled using tooth count, covering twin-train and multi-shaft applications with one card.

04How does the Keyphasor reference improve diagnostics in System 1?

When the rack includes a 3500/22M TDI, the 3500/25's synchronized phase/speed data lets System 1 build phase-referenced waveforms and Bode, Cascade, and Waterfall plots, and correlate vibration, temperature, and process events by rotational position.

05What setup data is needed to correctly scale a 3500/25 channel?

The transducer type, gap, and cable length, the targeting method (once-per-rev notch/keyway or gear tooth count), and the machine's minimum/maximum speed range are needed to configure accurate pulses-per-revolution scaling and anti-bounce filtering.