Bently Nevada 2789-204 Seismic Transducer | Velocity Sensor

Bently Nevada 2789-204 Seismic Transducer

The Bently Nevada 2789-204 is a precision seismic velocity transducer engineered for absolute vibration measurement on rotating and reciprocating machinery. Unlike proximity probes that measure relative shaft motion, this sensor captures the actual casing vibration—critical data for comprehensive machinery health assessment.

What Makes the 2789-204 Different?

Absolute Vibration Measurement: This seismic transducer measures the actual movement of the machine casing or bearing housing relative to free space, not just shaft displacement. This provides a complete picture of machinery dynamics that proximity probes alone cannot deliver.

Self-Generating Design: The 2789-204 uses a moving coil design that generates its own electrical signal proportional to velocity—no external power required. This passive design eliminates concerns about power supply noise or failure.

Core Specifications

• Model Number: 2789-204
• Measurement Type: Absolute velocity (seismic)
• Frequency Range: 10 Hz to 1000 Hz
• Sensitivity: 100 mV/in/sec nominal (4 mV/mm/sec)
• Mounting: Stud mount (10-32 UNF thread)
• Weight: 200 grams (0.44 lbs)
• Temperature Range: -40°C to +120°C (-40°F to +248°F)
• Housing: Hermetically sealed stainless steel
• Output: Differential voltage, low impedance

Where Should You Use This Sensor?

Bearing Housing Monitoring: Mount directly on bearing caps to detect bearing wear, misalignment, and lubrication issues before they escalate into failures.

Gearbox Surveillance: Capture gear mesh frequencies, sidebands, and modulation patterns that indicate tooth wear, eccentricity, or load distribution problems.

Motor and Generator Frames: Monitor electrical and mechanical anomalies including rotor bar defects, air gap eccentricity, and foundation looseness.

Reciprocating Compressors: Track crosshead motion, valve impacts, and piston slap in applications where proximity probes are impractical.

Pump Casings: Detect cavitation, impeller imbalance, and hydraulic instabilities in centrifugal and positive displacement pumps.

Why Velocity Measurement Matters

Velocity transducers like the 2789-204 are particularly effective at detecting mid-frequency faults (10-1000 Hz) where most machinery problems manifest. While accelerometers excel at high-frequency detection and proximity probes handle low-frequency shaft motion, velocity sensors occupy the sweet spot for general machinery condition monitoring—making them the workhorse of predictive maintenance programs.

Installation Best Practices

For optimal performance, mount the 2789-204 on a flat, clean surface using the integral stud. Ensure the mounting location provides a rigid mechanical path to the bearing or component being monitored. Avoid mounting on thin sheet metal, plastic covers, or locations with poor structural coupling. The sensor's axis should align with the direction of expected vibration (typically radial or axial).

System Compatibility

The 2789-204 integrates seamlessly with Bently Nevada 3300, 3500, and System 1 monitoring platforms, as well as third-party vibration analyzers and data acquisition systems. Its low-impedance output drives long cable runs without signal degradation, making it ideal for distributed monitoring architectures.

Condition: Brand new, factory-sealed with calibration certificate and full manufacturer warranty.