Bently Nevada 3500/50M 288062-02 Tachometer Module

3500/50M Tachometer Module is a dual-channel monitoring module under the 3500 Machinery Protection System, serving as a critical component of the 3500 series. It is specifically designed for speed monitoring and protection of rotating machinery, capable of accepting signals from proximity probes or magnetic pickups to accurately measure shaft rotational speed, rotor acceleration, and rotation direction. Through advanced signal processing technology, this module provides precise speed measurement and multi-level alarm functions, ensuring the safe and stable operation of rotating machinery.

The 3500/50M consists of a fixed front card (288062-02) and four different types of rear cards (see the Ordering page for details). Please note that model 133450-01 is generally not used with 288062-02, therefore this configuration option is not displayed.

Key Features
The 3500/50M Tachometer Module offers professional configuration capabilities and multi-parameter monitoring functions. Users can independently configure each channel via the 3500 Rack Configuration Software to support the following monitoring types:

• Speed Monitoring and Setpoint Alarming: Real-time monitoring of shaft speed, triggering alarms when speed exceeds or falls below set values

• Speed Band Alarming: Setting speed range bands, issuing alarms when speed exceeds preset ranges

• Zero Speed Notification: Detecting whether the rotor is in zero speed state, providing zero speed alarm function

• Rotor Acceleration Alarming: Monitoring rotor acceleration, triggering alarms when acceleration exceeds set values

• Reverse Rotation Notification: Detecting the rotation direction of the rotor, issuing alarms when reverse rotation occurs

Unique features of this module include:

• Keyphasor Signal Supply: Can provide conditioned Keyphasor signals to the backplane for use by other monitoring modules in the rack, eliminating the need for a separate Keyphasor module

• Peak Hold Function: Can record the highest speed, highest reverse speed, or number of reverse rotations reached by the machine, with software-resettable peak values

• Multiple Event Support: Supports 1 to 255 events per revolution, meeting the requirements of different gear tooth configurations

• Multiple Input Types: Supports both proximity probe and magnetic pickup signal input methods

The two channels of the monitor can operate independently, performing different monitoring functions. For example, Channel 1 can be used for speed monitoring and setpoint alarming, while Channel 2 can be used for rotor acceleration monitoring or reverse rotation detection. This flexible configuration enables a single monitor to meet the diverse monitoring needs of complex rotating machinery systems.

Working Principle
The core workflow of the 3500/50M Tachometer Module includes four stages: signal input, conditioning, parameter calculation, and alarm judgment:

1. Signal Input
   The module accepts analog signals from proximity probes or magnetic pickups
   Input signal range: +10.0 V to -24.0 V, signals exceeding this range are limited internally by the module
   Input impedance: 20 kΩ (standard), 40 kΩ (TMR), 7.15 kΩ (internal barrier version)
   Transducer power supply: 24 Vdc, maximum 40 mA per channel

2. Signal Conditioning
   Input signals are processed through amplification, filtering, etc., and converted into digital signals for processing:

• Auto Threshold: Applicable to any input above 0.0167 Hz (corresponding to 1 rpm for 1 event/revolution), minimum triggering signal amplitude is 1 V peak-to-peak

• Manual Threshold: User selectable from +9.5 Vdc to -23.5 Vdc, minimum triggering signal amplitude is 500 mV peak-to-peak

• Hysteresis Adjustment: Adjustable range 0.2 to 2.5 volts, preventing false triggering caused by signal jitter

3. Parameter Calculation
   Based on the configured monitoring type, the module calculates the following measured values:

• Rotor Speed: Speed, Speed Band, Peak Speed

• Rotor Acceleration: Rotor Acceleration, Speed, Peak Speed

• Zero Speed: Zero Speed, Speed, Peak Speed

• Reverse Rotation: Reverse Speed, Reverse Peak Speed, Speed (forward), Num Reverse Rotations

4. Alarm Judgment
   Each measured value can set two levels of alarm points:

• Alarm 1 Delay: 1-60 seconds, adjustable in 1-second intervals

• Alarm 2 Delay: 1-60 seconds, adjustable in 0.1-second intervals
  Alarm accuracy is as high as ±0.13% of the set value, ensuring timely and reliable response

Outputs & Communication

• Front Panel Indicators: Equipped with OK (operational status), TX/RX (communication status), and Bypass (bypass status) LEDs

• Buffered Transducer Outputs: One coaxial connector per channel, providing short-circuit and ESD protection

• Recorder Outputs: 4-20 mA current signal, proportional to full scale (rpm or rpm/min), independent output per channel. Short circuits do not affect operation

• Communication Interface: Communicates with other modules in the 3500 rack via the backplane, supporting remote monitoring and data integration

Technical Characteristics

1. High-Precision Measurement:

• Below 100 rpm: ±0.1 rpm

• 100-10,000 rpm: ±1 rpm

• 10,000-99,999 rpm: ±0.01% of true shaft speed

• Acceleration accuracy: ±20 rpm/min

2. Wide Range Capability:

• Maximum full scale: 99,999 rpm

• Maximum input frequency: 20 kHz

• Minimum input frequency for proximity probes: 0.0167 Hz (corresponding to 1 rpm for 1 event/revolution)

• Minimum input frequency for magnetic pickups: 3.3 Hz

3. Flexible Input Configuration:

• Supports 1-255 events/revolution (for rotor acceleration and zero speed channel types)

• Other channel types support 0.0039-255 events/revolution

Environmental Adaptability:

• Operating temperature range: -20°C to +65°C (with internal barrier version)

• Storage temperature range: -40°C to +85°C

Safety Certifications:

• Complies with FCC, EMC, LV Directive, RoHS, ATEX, IECEx, CSA and other international standards

• Suitable for hazardous areas (Class I, Division 2/Groups A,B,C,D or Class I, Zone 2)

Important Warning
It is important to note that the 3500/50M Tachometer Module must not be used independently or as a component of a speed control or overspeed protection system, as it does not provide protective redundancy or the response speed required for reliable operation as a speed control or overspeed protection system. The analog proportional output is suitable for data logging, chart recording, or display purposes only. Speed alert setpoints are suitable for annunciation purposes only.

For magnetic pickups: Do not use magnetic pickups for the reverse rotation option or zero speed option, otherwise false indications of rotation direction may occur. The transducers do not provide a clean edge for the detection circuit during low speeds.

Physical Characteristics
Monitor Module (Main Board):
Dimensions: 241.3 mm × 24.4 mm × 241.8 mm
Weight: 0.82 kg

I/O Modules:
Non-barrier version: 241.3 mm × 24.4 mm × 99.1 mm, weight 0.20 kg
Internal barrier version: 241.3 mm × 24.4 mm × 163.1 mm, weight 0.46 kg

Rack Space Requirements:
Monitor Module: Occupies 1 front slot
I/O Module: Occupies 1 rear slot

Applications
The 3500/50M Tachometer Module is specifically designed for rotating machinery in the following fields:

• Power Plants: Speed monitoring and protection for steam turbines, gas turbines, and hydro turbines

• Petrochemical Industry: Speed monitoring and overspeed protection for compressors and pumps

• Metallurgical Industry: Speed monitoring for rolling mills and fans

• Marine Propulsion: Speed and rotation direction monitoring for propulsion shaft systems

• Industrial Drives: Speed monitoring for large motors and gearboxes