Description

Overview

The 3500/50 Tachometer Module (133450-01) is a dual-channel monitoring module designed for precise measurement of shaft rotational behavior in rotating machinery protection systems. It integrates speed, acceleration, and directional analysis within the 3500 rack platform and is intended for continuous condition monitoring of turbines, compressors, motors, and other critical assets.

Measurement Capabilities

This module processes input signals from proximity probes and magnetic pickups to derive multiple operational parameters:

• Rotational speed measurement in RPM or Hz

• Rotor acceleration calculation (speed rate-of-change)

• Reverse rotation detection and alarming

• Zero-speed detection for startup/shutdown monitoring

• Speed band and threshold-based alarm logic

• Peak value capture (maximum speed, reverse rotation events)

Signal conditioning and Keyphasor-style reference output are provided to the rack backplane for synchronization and system-level diagnostics.

Input Characteristics

• Two fully independent input channels

• Compatible transducers:

• Eddy current proximity probes (recommended for full functionality)

• Magnetic pickups (limited low-speed performance)

• Input voltage range: +10 V to –24 V

• Input impedance options:

• 20 kΩ standard configuration

• 40 kΩ TMR configuration

• 7.15 kΩ internal barrier version

• Maximum input frequency: up to 20 kHz (application-dependent)

• Low-speed detection:

• Proximity probes support near-zero operation

• Magnetic pickups limited at very low RPM ranges

Output & Interface Functions

• Buffered signal output via coaxial connectors (per channel)

• Conditioned Keyphasor signal distributed to rack backplane

• Front-panel indicators:

• Module OK status

• Communication activity (TX/RX)

• Bypass mode status

• Analog proportional outputs available for trending and diagnostics (non-protection use)

Operating Modes

Selectable configuration profiles include:

• Speed monitoring with alarm setpoints

• Speed + zero-speed detection logic

• Speed + rotor acceleration analysis

• Speed + reverse rotation protection logic

• Speed band monitoring for operational stability zones

Configuration is managed through 3500 rack configuration software.

Electrical & Environmental Data

• Typical power consumption: 5.8 W

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

• Relative humidity: up to 95% non-condensing

• Compliance: CE, CSA and industrial EMC standards

Applications

• Steam and gas turbines

• Centrifugal compressors

• Industrial electric motors

• Expansion turbines

• High-speed rotating equipment protection systems

FAQ

Q1: Can this module operate without proximity probes?
It can accept magnetic pickups, but full low-speed and reverse detection performance requires proximity probes.

Q2: Is this module suitable for zero-speed detection?
Yes, when used with proximity probes, it supports reliable near-zero RPM detection.

Q3: Does it provide protection-level outputs?
It provides alarm logic and Keyphasor signals, integrated into the 3500 protection rack architecture.

Specifications

• Brand: Bently Nevada

Advantages

• High reliability in industrial environments
• Supports continuous operation
• Compatible with major PLC/DCS systems