Bently Nevada 3500/42M 138700-01 Shaft Absolute I/O Module

Product Overview

The Bently Nevada 3500/42M (Part Number: 138700-01) is a specialized Shaft Absolute I/O module designed to interface directly with the 3500/42M Proximitor Seismic Monitor group. This version is specifically engineered for use with External Termination (ET) blocks, allowing field wiring to be consolidated inside multi-terminal cabinets rather than directly on the back of the machinery protection rack. The 138700-01 accepts input channels from non-contact proximity probes, Velomitor piezo-velocity sensors, and Seismoprobe moving-coil transducers, enabling comprehensive shaft absolute vibration calculation and case expansion diagnostics on critical turbo-machinery assets.

Technical Configuration

Core Technical Advantages

The 138700-01 Shaft Absolute I/O module features an ultra-lightweight, compact structural footprint that mounts directly into the rear slots of the standard 3500 chassis backplane. It processes complex signal conditioning paths simultaneously across multiple sensor lines, offering tailored power footprints depending on transducer combinations. The hardware includes internal circuit isolation to shield adjacent monitor channels from field-induced electrical noise or ground loop faults, maintaining uninterrupted diagnostic tracking loops in high-stress, high-load plant environments.

Technical Specifications

Installation Guide

Mechanical Backplane Assembly

Locate the corresponding rear slot assigned to the main 3500/42M Proximitor Seismic Monitor card in the front of the rack. Slide the 138700-01 I/O module into the rear slots along the alignment channels. Push firmly until the module fits completely into the backplane connector array, then secure the two integrated captive mounting screws to achieve a dependable mechanical ground connection.

External Termination Infrastructure

Connect the specialized multi-conductor external termination cable from the high-density centronic plug on the 138700-01 module panel to the remote ET block positioned in the marshaling cabinet. Keep the cable free from sharp structural edges and clamp it firmly to avoid mechanical strain on the connection interfaces.

Field Transducer Wiring

Land individual field wiring leads from proximity probes, Velomitors, or Seismoprobes directly onto the terminal strip screws of the remote ET block. Use high-quality twisted, shielded cables for all field wiring runs. Ground the shields exclusively at the termination block ground strip to isolate sensor data channels from electromagnetic interference.

Engineering Advantages

Consolidated Multi-Sensor Processing

The 138700-01 module eliminates the need for separate, dedicated sensor interfaces by routing different transducer lines through a single multi-channel I/O module. This consolidated processing enables the 3500 system to combine casing and relative shaft displacement parameters into real-time shaft absolute vibration metrics dynamically.

Streamlined Maintenance and Safety

The external termination architecture increases plant safety by keeping field maintenance technicians clear of live power modules on the core protection rack during testing loops. Because connections terminate on a separate cabinet block, engineers can test and isolate individual channel lines without disturbing adjacent active channels.

Technical FAQs

Q1: Can I use this I/O module with standard internal termination screw blocks?

A1: No. The 138700-01 is built specifically with high-density pin ports for external termination setups. If your installation requires wiring landing directly onto the back of the 3500 rack, use the internal termination variant of the 3500/42M I/O module instead.

Q2: Why do the power supply voltages vary significantly between Velomitor and Seismoprobe setups?

A2: The module adjusts its internal power rails dynamically based on configuration. Proximity sensors and Velomitors require an active constant current loop supply (23.9 V), while passive moving-coil Seismoprobes require a lower bias voltage configuration (6.82 V) to measure sensor coil displacement accurately.

Q3: Does the 138700-01 I/O module operate independently inside the rack?

A3: No. The 138700-01 is a routing hardware component. It must pair directly with a front-slot 3500/42M Proximitor Seismic Monitor card, which runs the signal processing algorithms and diagnostic logic routines.