Bently Nevada Module 3500/25

The Bently Nevada 3500/25 is a half-height, two-channel Enhanced Keyphasor Module designed for the 3500 series Machinery Protection System. It provides critical Keyphasor reference signals to monitor modules within the 3500 rack, enabling precise rotational speed measurement and vibration phase analysis on turbines, compressors, generators, and other rotating machinery .

Key Features & Benefits

Feature	Description
Form Factor	Half-height, two-channel module requiring 1 half-height front slot (main module) and 1 full-height rear slot (I/O module) .
Input Compatibility	Accepts up to two transducer signals from proximity probes or magnetic pickups .
Input Signal Range	Non-isolated I/O: +0.8 V to -21.0 V Isolated I/O: +5 V to -11 V .
Input Impedance	21.8 kΩ minimum .
Speed/Frequency Range	Input: 1 to 1,200,000 cpm (0.017 to 20 kHz) Output: 1 to 99,999 cpm (0.017 to 1667 Hz) .
Power Consumption	3.2 Watts typical .
Transducer Power Supply	–24 VDC, 40 mA maximum per channel .
Outputs	Two buffered Keyphasor outputs via front coaxial connectors; two additional buffered outputs via rear Euro-style connectors .
Output Impedance	504 Ω maximum (buffered) .

Model Number Breakdown (3500/25-XX-XX-XX)

Field	Description
3500/25	Base model — Enhanced Keyphasor Module
First Field	I/O Module Type (e.g., 01 = Standard, 03 = etc.)
Second Field	Options / Approvals
Third Field	Agency Approvals (e.g., 00 = None, 02 = CSA/ATEX)

The module's PWA 149369-01 fully replaces the earlier PWA 125792-01 design, offering expanded signal processing capabilities while maintaining complete downward compatibility in form, fit, and function for use in legacy systems .

Transducer Conditioning & Accuracy

Parameter	Specification
Auto Threshold	Minimum trigger amplitude: 2 V peak-to-peak; Minimum frequency: 120 rpm (2 Hz) .
Manual Threshold	User-selectable from 0 to –20 VDC; Minimum trigger amplitude: 500 mV peak-to-peak .
Hysteresis	User-selectable from 0.2 to 2.5 Volts .
Speed Accuracy (Non-processed)	0.017–100 Hz: ±1 cpm; 101–500 Hz: ±8 cpm; 501 Hz–20 kHz: ±1% of cpm .
Speed Accuracy (Processed)	0.017–60 Hz: ±1 cpm; 61–150 Hz: ±8 cpm; 151 Hz–20 kHz: ±1% of cpm .

System Configuration & Redundancy

Maximum Keyphasor Signals: The 3500 system can accept up to 4 Keyphasor signals in normal configuration and up to 8 signals in a paired configuration .
TMR (Triple Modular Redundant) Applications: When system Keyphasor input is required for TMR, the system should employ two Keyphasor modules operating in parallel to provide primary and secondary signals .
Pairing Configuration: Systems with more than four Keyphasor inputs can use a paired arrangement, requiring two consecutive monitoring positions (upper/lower slots or two half-slots) .

Front Panel LED Indicators

LED	Indication
OK LED	Indicates when a fault has been detected in the Keyphasor Module .
TX/RX LED	Indicates when the module is communicating with the Rack Interface Module (RIM) .

Environmental Limits

Parameter	Specification
Operating Temperature (Standard)	–30°C to +65°C (–22°F to +150°F) .
Operating Temperature (Internal Barrier I/O)	0°C to +65°C (32°F to +150°F) .
Storage Temperature	–40°C to +85°C (–40°F to +185°F) .
Humidity	95%, non-condensing .

Physical Specifications

Component	Dimensions	Weight
Main Module	119.9 mm x 24.4 mm x 256.5 mm (4.72 x 0.96 x 10.10 in)	0.34 kg (0.76 lbs) .
I/O Module	241.3 mm x 24.4 mm x 103.1 mm (9.50 x 0.96 x 4.06 in)	0.46 kg (1.01 lbs) .