The Bently Nevada 990-05-XX-01-00 (including MOD:165335-01) is a high-performance, two-wire vibration transmitter designed to provide a 4 to 20 mA output proportional to the overall vibration level of rotating machinery. This module bridges the gap between complex machinery protection systems and standard Programmable Logic Controllers (PLCs) or Distributed Control Systems (DCS). By integrating the Proximitor sensor's signal processing directly into a transmitter format, it allows for cost-effective, continuous monitoring of pumps, fans, and motors without the need for dedicated rack-based monitors. The MOD:165335-01 designation typically signifies a specific modification or factory-configured enhancement tailored for specialized industrial integration.
| Feature | Specification |
| Output Signal | 4 to 20 mA DC (Proportional to peak-to-peak vibration) |
| Input Type | Accepts signal from 3300 NSv Proximity Probe |
| Power Requirement | 12 to 35 Vdc (Loop Powered) |
| Measurement Range | 0 to 125 µm (5 mils) peak-to-peak (standard) |
| Frequency Response | 10 Hz to 1,000 Hz (600 to 60,000 cpm) |
| Operating Temperature | -35 °C to +85 °C (-31 °F to +185 °F) |
| Loop Resistance | Maximum $R_L = (V_{supply} - 12) / 0.02$ |
| Enclosure Material | Aluminum (Polycarbonate cover) |
The part numbering for the 990 series follows a precise logic to ensure compatibility with your existing sensor chain and control loop.
990: The base series designation for the Bently Nevada Vibration Transmitter.
-05: Full-scale Option. This signifies a standard measurement range (typically 0-5 mils or 0-125 µm), calibrated for the displacement of the target material.
-XX: System Length Option. These digits indicate the total calibrated length of the probe and extension cable (e.g., 5.0 meters or 7.0 meters).
-01: Mounting Option. This specifies the 35mm DIN-rail mounting hardware, allowing for easy installation in local junction boxes or control cabinets.
-00: Agency Approval Option. Indicates standard approvals without specialized hazardous area certifications (e.g., non-Ex).
MOD:165335-01: A Modification code representing a factory-authorized deviation or custom calibration setting specifically engineered for high-reliability applications.
Success in monitoring depends heavily on the integrity of the loop and the grounding strategy.
Probe Clearance: Ensure the 3300 NSv probe is gapped correctly before connecting to the 990 Transmitter. Incorrect gapping will result in a clamped 4mA or 20mA signal (bottoming out or saturation).
Wiring the Loop: Connect the "Power" and "Signal" terminals in a series loop with your 24V DC power supply and the PLC/DCS analog input card.
Shielding: Use twisted, shielded pair cabling. The shield should be grounded at the control system end only. This prevents ground loops that can introduce artificial "noise" into your vibration data.
DIN Rail Grounding: Ensure the DIN rail itself is well-grounded to the cabinet earth to provide a path for EMI/RFI dissipation.
MOD Verification: If replacing an existing unit, verify that the MOD:165335-01 matches the previous unit to ensure the 4-20 mA scaling remains consistent in your software.
Q: Can I use this transmitter with a standard 3300 XL 8mm probe?
A: No. The 990 Transmitter is specifically designed to work with the 3300 NSv (Near Surface) probe and extension cable. Using an 8mm probe will result in incorrect calibration.
Q: What does the "MOD" number signify?
A: Modification numbers (MOD) are used by Bently Nevada to denote specialized internal settings, such as custom frequency filters or specific full-scale ranges not covered by the standard options.
Q: How do I perform a field check on the 4-20 mA output?
A: You can simulate vibration or use a gap voltage measurement at the "Prox Out" and "Com" terminals using a high-impedance voltmeter to verify the transmitter is receiving a valid signal from the probe.
