Description

Configured for continuous machinery vibration monitoring in Turbomachinery Instrumentation Systems (TSI), the Bently Nevada 3300/25, also cataloged as the 3300/25 Dual Accelerometer Monitor, provides direct physical/electrical execution. This module processes signals from two independent accelerometer transducers, transforming raw acceleration waveforms into engineering units for absolute shaft and casing vibration assessment. The hardware performs continuous peak-to-peak or RMS amplitude calculations, driving internal alarm relays and proportional analog outputs to protect critical rotating assets.

Hardware Specifications

Eddy-Current Probe Scaling and Cross-Talk Suppression

While processing dynamic acceleration profiles, the monitor interfaces with proximity systems where eddy-current probe scaling requires validation. The internal circuitry implements cross-talk suppression algorithms to isolate high-frequency carrier frequencies between adjacent sensor paths. Proper calibration enforces gap voltage validation, targeting -10 VDC levels to maintain linear operation across the specified transducer scale. This signal conditioning isolates structural housing vibration from internal rotor dynamics, preventing false trips while capturing genuine casing acceleration events.

Frequently Asked Questions

Q: How does the monitor respond to a transducer fault condition?

A: The monitor contains a dedicated “Not OK” circuit that continuously assesses the transducer biasing voltage. If the input signal drops outside the defined windows, the Not OK LED illuminates, the Not OK relay changes state, and the Alert and Danger relays are suppressed to prevent false machine trips.

Q: Can the 4-20 mA recorder outputs drive isolated and non-isolated loads simultaneously?

A: The analog recorder outputs are single-ended and share a common chassis ground. Connecting to non-isolated external systems requires external loop isolators to eliminate ground loop interference and preserve signal accuracy.

Field Installation Guidelines

• Chassis Insertion: Ensure the 3300 system rack is completely powered down before inserting or removing the monitor module. Secure the top and bottom chassis screws to guarantee structural stability and solid backplane connection.
• Shield Termination: Terminate transducer cable shields exclusively at the system monitor backplane ground bus. Do not ground the shield at the field junction box or sensor housing to avoid ground loop currents.
• Wiring Separation: Route transducer input wiring through dedicated, grounded metallic conduits separate from high-voltage AC power lines to minimize electromagnetic cross-talk.