The 3500/42M 4-channel universal monitoring module is part of the Bently Nevada 3500 Machinery Protection System and provides flexible, high-performance monitoring for a wide range of rotating machinery applications.

Each channel can be independently configured to process either eddy current proximity probe signals (displacement, vibration, eccentricity, differential expansion) or seismic sensor signals (velocity or acceleration). The module supports alarm and trip logic, relay outputs, and 4–20 mA analog outputs, making it suitable for both machinery protection and condition monitoring.

Core Functions

Universal monitoring for proximity and seismic sensors

Monitoring of displacement, vibration, eccentricity, and differential expansion

Velocity and acceleration measurement for casing and bearing vibration

Programmable alarms, trips, and interlocks

Supports mechanical protection and machinery status monitoring

System & Sensor Compatibility

Bently Nevada 3500 system I/O rack

Compatible sensors include:

3300 / 3301 series eddy current probes

330500 series seismic sensors

330700 series bearing vibration sensors

Installation & Mechanical Specifications

Installation method: 3500 standard rack card-slot installation

Power and communication via rack backplane

Protection level: IP20 (installed inside control cabinet)

Front panel indicators:

OK

TX / RX

Bypass (independent bypass per channel)

Weight: approx. 0.9 kg

Power Supply

Powered from 3500 rack backplane

Sensor excitation: –24 V DC

Key Technical Parameters

Channel Configuration

4 independent, fully programmable channels

Each channel configurable as:

Preamplifier mode

Seismic mode

Input Types

Preamplifier mode:

Eddy current probe signals

Displacement, vibration, phase reference

Seismic mode:

Velocity or acceleration signals

Sensor Sensitivity

Eddy current probes:

3.94 mV/mil (155 mV/mm)

Seismic (velocity):

Default 20 mV/mm/s

Signal Conditioning & Processing

Programmable measurements including:

Static (DC) values

1X / 2X amplitude and phase

Peak and RMS values

Programmable filtering: 0.1 Hz to 1 kHz

Outputs

Buffered sensor output per channel

Short-circuit protected

4–20 mA analog outputs

Relay alarm and trip outputs (programmable)

Power Consumption

Typical: 8.5 W

Environmental Conditions

Operating temperature: –30 °C to +65 °C

Relative humidity: 5% to 95%, non-condensing

Software & Firmware Compatibility

3500 Rack Configuration Software: V3.30 or later

Module firmware: Revision 2.2 or later

Safety & Reliability

Suitable for SIL 2 mechanical protection circuits

Designed for high-availability rotating machinery protection systems

Typical Applications

Turbine and compressor vibration monitoring

Bearing and casing vibration protection

Differential expansion and eccentricity monitoring

Critical rotating machinery protection and diagnostics

BENTLY 3500/42 125972-02 Proximitor/Seismic Monitor