Description

Product Description

The 3500/50 Tachometer Module (134938-01) is a dual-channel monitoring unit designed for continuous evaluation of rotational dynamics in high-value machinery. It is integrated into the Bently Nevada 3500 rack platform and supports real-time monitoring of speed behavior, transient events, and directional changes for protection and diagnostics.

The module processes signals from proximity probes and magnetic pickup sensors, converting raw pulse data into actionable machinery parameters such as rotational speed, acceleration, and direction status.

Signal Processing Capabilities

The module supports multiple measurement functions derived from shaft rotational input:

• Continuous shaft speed measurement in RPM or Hz

• Rotor acceleration calculation (RPM per second)

• Zero-speed detection during startup and shutdown conditions

• Reverse rotation identification and event logging

• Speed band monitoring for defined operating ranges

• Peak capture for maximum and reverse rotational events

Signal conditioning ensures stable Keyphasor-style reference output distributed through the rack backplane for system synchronization.

Input Specifications

• Dual independent input channels

• Sensor compatibility:

• Eddy current proximity probes (preferred for full capability range)

• Magnetic pickups (usable but limited at low-speed and directional detection scenarios)

• Input voltage range: +10 V to –24 V DC

• Input impedance: 20 kΩ

• Maximum frequency response: up to 20 kHz (sensor dependent)

• Low-speed detection behavior:

• Near-zero detection supported with proximity probes

• Magnetic pickups limited by waveform stability at low RPM

Output Interfaces

• Per-channel buffered signal output via coaxial connectors

• Conditioned Keyphasor signal distributed to rack backplane

• Front-panel diagnostic indicators:

• Module health status (OK)

• Communication activity (TX/RX)

• Bypass mode indication

• Analog proportional outputs available for trending and external visualization (non-protective function)

Operating Configuration Modes

The module supports multiple configurable logic profiles via 3500 rack software:

• Speed monitoring with threshold-based alarms

• Speed monitoring with zero-speed detection logic

• Combined speed and rotor acceleration analysis

• Speed monitoring with reverse rotation protection

• Speed band control for operational envelope supervision

Each mode is selected based on machine type and protection strategy.

Electrical and Environmental Data

• Typical power consumption: 5.8 W

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

• Relative humidity tolerance: up to 95% non-condensing

• Compliance: CE, CSA, and industrial EMC requirements

Application Scope

• Steam and gas turbine monitoring

• Centrifugal and axial compressors

• Industrial pump systems

• Electric motor driven rotating assemblies

• High-speed rotating machinery protection systems

FAQ

Q1: Can magnetic pickups be used for full functionality?
They can be used for speed measurement, but proximity probes are required for reliable low-speed, reverse rotation, and zero-speed detection.

Q2: Is this module suitable for protection systems?
Yes, it is designed as part of the 3500 rack protection and monitoring architecture.

Q3: Does it support acceleration-based alarms?
Yes, rotor acceleration monitoring can be enabled through configuration modes.

Specifications

• Brand: Bently Nevada

Advantages

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