Configured for displacement and vibration measurements in machinery protection systems, the Bently Nevada 330850-51-CN (330850 Proximitor Sensor) provides direct physical/electrical execution. This signal conditioning hardware processes high-frequency carrier signals from a 25 mm proximity probe, converting inductive impedance changes into a proportional voltage output ranging from -2 VDC to -18 VDC. The unit serves as the interface between the transducer and monitoring instrumentation, supporting continuous observation of shaft dynamic behavior.

Part Number Configuration

• 330850: 3300 XL 25 mm Proximitor Sensor.

• 51: System length option (5.0 meters / 16.4 feet system).

• CN: Agency approval option (China-specific compliance).

Hardware Specifications

Eddy-Current Probe Scaling and Rotor Dynamics

The 25 mm proximity sensing system is optimized for target surfaces where large gap measurements are required. Accurate eddy-current probe scaling is mandatory, requiring the system to be calibrated against AISI 4140 steel. Field technicians must perform gap voltage validation (-10 VDC targets) at the Proximitor output during setup to ensure the probe tip is centered within the 1.0 mm to 3.0 mm linear range. Proper scaling is critical for reliable rotor dynamics analysis, particularly when monitoring large-clearance fluid-film bearings. Cross-talk suppression must be enforced by maintaining required spatial separation between multiple sensors to prevent electromagnetic interference within the high-frequency measurement loop.

Ordering Info

• 1 330850-51-CN Proximitor Sensor

• 1 Technical Data Sheet

• 1 Installation Reference Guide

Field Installation Guidelines

• Mounting Requirements

• Secure the Proximitor to a DIN-rail or standard mounting plate within a clean, dry enclosure to ensure long-term stability.

• Ensure the mounting surface is grounded to a common instrumentation reference to minimize electrical noise.

• Wiring and Signal Integrity

• Utilize shielded twisted-pair cabling for all output signal paths to the monitor.

• Maintain physical separation from high-voltage AC cables to avoid signal degradation or induction.

• Verify that the -18 VDC to -24 VDC power supply remains within the specified range to avoid output voltage clipping.

Frequently Asked Questions

• Is the Proximitor output signal compatible with PLC analog input cards?

  The output is a negative DC voltage. A signal converter or an appropriate negative-voltage-capable analog input module is required for integration.

• Can this Proximitor be used with a 5 m or 9 m system cable?

  The model 330850-51-CN is specifically calibrated for a 5.0 m system length; deviation from this length will alter the system impedance and calibration.

• Is the device hot-swappable during system operation?

  The sensor can be removed while the loop is powered, but this will trigger a channel fault or "Not OK" status in the connected monitoring system.

• How do I verify the linear range in the field?

  Using a static calibration fixture or a manual micrometer, verify the voltage change matches the 7.87 V/mm sensitivity as the probe moves through the 1-3 mm range.

• What happens if the supply voltage drops below -18 VDC?

  The Proximitor will fail to maintain the necessary carrier wave amplitude, resulting in increased signal noise or complete loss of the output voltage signal.

• Does this sensor support HART or digital communication protocols?

  No, the 330850 is a purely analog signal conditioning device and does not support digital handshaking or HART protocol modulation.

• How should I clean the coaxial connector during installation?

  Use a clean, dry, non-conductive electronic contact cleaner. Ensure no residue remains, as it can cause impedance shifts in the high-frequency path.

• What is the impact of an "Open" or "Short" circuit in the probe lead?

  An open or short circuit will cause the Proximitor output to swing to the negative supply rail or ground, triggering an "Not OK" status in the monitor.