Bently Nevada 3500/50 Tachometer with Keyphasor Output

Product Overview

The Bently Nevada 3500/50 (Part Number 133388-02) acts as the primary speed and rotational monitoring hub for the 3500 Machinery Protection System. This dual-channel module processes signals from proximity probes and magnetic pickups to provide high-accuracy data on shaft speed, rotor acceleration, and direction. It serves as a critical safety layer for high-speed turbines and compressors by identifying overspeed and reverse rotation conditions instantly. We offer this module as 100% brand new and original, delivered in factory-sealed packaging.

Part Number Breakdown: 3500/50-AA-BB-CC

• 01 (AA): I/O Module with Internal Terminations (standard configuration for simplified rack wiring).

• 00 (BB): Standard Agency Approval (suitable for non-hazardous or standard industrial environments).

• 01 (CC): Internal Termination I/O Module (integrated connection interface).

• 133388-02: The hardware part number representing the specific Tachometer Module circuit board.

Technical Specifications

Engineering Advantages

Integrated Keyphasor® Conditioning

The 3500/50 eliminates the need for separate Keyphasor modules in many configurations. It conditions the raw input signal and distributes it across the 3500 rack backplane. This allows other monitors (vibration, position, or temperature) to utilize the phase reference for synchronous data acquisition, reducing total hardware footprint and cost.

Advanced Peak Hold Memory

Industrial transients often occur too fast for human observation. The 133388-02 includes non-volatile peak hold registers that store the maximum speed, maximum reverse speed, and total reverse rotation count. This data provides forensic evidence during post-trip analysis, helping engineers determine the exact mechanical state at the moment of failure.

Zero-Speed and Reverse Rotation Logic

Unlike basic tachometers that only track positive RPM, this module detects rotor direction and zero-speed thresholds. This prevents starter motor engagement during "roll-back" or slow-rotation phases, protecting the drive train and couplings from torque-related damage during startup or coast-down sequences.

High-Frequency Signal Stability

The module employs sophisticated analog-to-digital filtering to handle high-frequency pulse trains from gear teeth or multi-event wheels. This prevents "signal jitter" and nuisance overspeed trips caused by electromagnetic interference (EMI) or shaft runout, ensuring that the safety system only reacts to genuine mechanical speed excursions.

FAQs

Does the 3500/50-01-00-01 support internal or external terminations?

The -01 option indicates Internal Terminations. This means you connect the field wiring directly to the terminal strips on the I/O module at the rear of the 3500 rack, removing the need for external terminal blocks and additional interconnect cables.

How does the module handle a "Gap Out" on a proximity probe?

If a proximity probe moves out of range or fails, the 3500/50 detects an invalid bias voltage. It immediately illuminates the "Bypass" and "OK" LEDs to signal a fault. The module then inhibits the overspeed trip for that specific channel to prevent a false machine shutdown.

Can I configure different pulse-per-revolution (PPR) counts for each channel?

Yes. Through the 3500 Rack Configuration Software, you define the PPR independently for Channel 1 and Channel 2. This allows you to monitor two different shafts or use different target geometries (e.g., a single keyway on one shaft and a 60-tooth gear on another) within the same module.

Is this module compatible with older magnetic pickups?

The 3500/50 supports a wide input range (+10 V to -24 V), making it compatible with most passive magnetic pickups and active proximity sensors. It provides the necessary power for Bently Nevada 3300 XL probes while remaining sensitive enough to trigger from the low-voltage pulses generated by magnetic pickups at low RPM.