Bently Nevada 990-04-70-02-00 Vibration Transmitter

Bently Nevada 990-04-70-02-00 Vibration Transmitter

The Bently Nevada 990-04-70-02-00, also cataloged as the 990 Vibration Transmitter, operates as a dedicated hardware component for converting proximity probe signals into a proportional 4-20 mA loop-powered output within machinery control and protection systems. The two-wire device conditions raw eddy-current inputs from a 3300 NSv proximity probe into peak-to-peak vibration amplitude values.

Suffix Breakdown & Model Matrix

The full part number designates specific factory configurations for scaling, cable length, mounting, and certifications:

• 04: Full-scale option rated for 0-4 mils pp (0-100 um pp).
• 70: System length option specified for 7.0 meters (23.0 feet).
• 02: Mounting option configured for bulkhead screws.
• 00: Agency approval option designated as not required.

Hardware Specifications

Gap Voltage Validation & Signal Conditioning

The integrated Proximitor sensor electronics demand precise gap voltage validation (-10 VDC targets) during proximity probe positioning to ensure optimal eddy-current probe scaling. Proper mechanical alignment prevents signal clipping and maintains linear conversion across the entire full-scale displacement range. To eliminate false trips during rotor dynamics transitions, the onboard Not OK/Signal Defeat circuit suppresses cross-talk and isolates the 4-20 mA output loop immediately upon detecting a loose coaxial connection or probe failure.

Frequently Asked Questions

Q: Can the dynamic vibration signal be captured while the transmitter is online?

A: Yes. The transmitter incorporates non-isolated PROX OUT and COM terminals alongside a physical coaxial connector. This architecture permits field test equipment or data collectors to tap the raw gap voltage and dynamic vibration signal simultaneously without interrupting the primary 4-20 mA process loop.

Q: How is the 4-20 mA loop calibrated or adjusted in the field?

A: Loop calibration is performed via non-interacting zero and span potentiometers located directly under the transmitter label. Additionally, a dedicated Test Input pin permits the introduction of a function generator signal to simulate operational conditions and verify loop output limits.

Field Installation Guidelines

• Mounting Alignment: Secure the transmitter package using the designated bulkhead screws. Ensure the installation surface is free of mechanical resonance that matches rotor dynamics frequencies.
• Wiring Protocols: Route the two-wire loop power cabling through dedicated, grounded conduits. Maintain separation between high-voltage power lines and the low-voltage sensor lines to prevent electromagnetic cross-talk.
• Shielding and Grounding: Proximity probe extension cables must be firmly seated into the coaxial connector. Ground all outer cable shields at a single, well-defined reference point, typically at the receiver/control cabinet chassis, to eliminate ground loops.