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Product Overview

The Bently Nevada 134938-01 3500/50 is a 2-channel tachometer module for industrial machinery monitoring.
It accepts signals from proximity probes or magnetic pickups to measure shaft speed, rotor acceleration, and rotor direction.
The module triggers alarms when user-defined thresholds are exceeded and can provide conditioned Keyphasor signals to the 3500 rack.

Key Features

• Model: 134938-01
• Product Type: 3500/50 Tachometer Module
• Channels: 2
• Input Sources: Proximity probes or magnetic pickups
• Keyphasor Outputs: Eliminates need for separate Keyphasor module
• Peak Hold Function: Stores highest speed, reverse speed, or reverse rotation count

Inputs & Signal Conditioning

• Input Signal Range: +10.0 V to -24.0 V
• Input Impedance: 20 kΩ (standard), 40 kΩ (TMR), 7.15 kΩ (internal barrier)
• Power Consumption: 5.8 W typical
• Supported Events per Revolution: 1–255 for Rotor Acceleration and Zero Speed
• RPM Range: Up to 99,999 RPM
• Minimum Input Frequency: 0.0167 Hz (proximity), 3.3 Hz (magnetic pickups)
• Accuracy:
  • <100 RPM: ±0.1 RPM
  • 100–10,000 RPM: ±1 RPM
  • 10,000–99,999 RPM: ±0.01% of true shaft speed
  • RPM/Min: ±20 RPM/min

Outputs

• Front Panel LEDs: OK, TX/RX, Bypass
• Buffered Transducer Outputs: Coaxial connectors, short-circuit and ESD protected
• Recorder Outputs: +4 to +20 mA, individual per channel, 550 Ω impedance
• Transducer Power Supply: 24 Vdc, 40 mA max per channel

Alarm & Monitoring Functions

• Speed Monitoring & Setpoint Alarming
• Speed Band Alarming, Zero Speed, Rotor Acceleration, Reverse Rotation Notifications
• Programmable Alarm Setpoints: Two per channel
• Alarm Time Delays: 1–60 s (0.1 s increments)

Physical & Environmental Specifications

• Dimensions: 241.3 × 24.4 × 241.8 mm (HxWxD)
• Weight: 0.82 kg (1.8 lb)
• Operating Temperature:
  • Internal/External Termination: -30°C to +65°C
  • Internal Barrier: 0°C to +65°C
• Storage Temperature: -40°C to +85°C
• Humidity: 95% non-condensing

This tachometer module provides accurate speed and rotor monitoring, essential for industrial machinery protection and predictive maintenance in 3500 series monitoring systems.