Description

The Bently Nevada 990-05-50-02-01 is a loop-powered, 2-wire vibration transmitter designed primarily for Original Equipment Manufacturers (OEMs) of centrifugal air compressors, small pumps, motors, or fans. This device integrates the functionality of a Proximitor sensor into a compact transmitter housing that interfaces with a 3300 NSv proximity probe. It outputs a standard 4-20 mA analog signal directly proportional to relative vibration, allowing for seamless integration into control systems without specialized monitoring racks.

Suffix Part Number Breakdown

The specific option strings map directly to the following structural specifications:

• 990: Base Model Number for the 990 Vibration Transmitter.
• 05: 0-5 mils peak-to-peak (0–125 µm pp) full-scale range.
• 50: 5.0 metres (16.4 feet) total electrical system length.
• 02: Bulkhead screw mounting option.
• 01: CSA Division 2 hazardous area approval rating.

Hardware Specifications

Functional Design and Safety Characteristics

The 990 transmitter incorporates potted engineering construction, rendering it highly resilient against 100% condensing humidity and typical process fluid splashes. Because it combines proximity signal conditioning and 4-20 mA output generation inside a single unit, it simplifies field loops by omitting separate intermediate signal processors.

The module features an integrated Not OK / Signal Defeat circuit. If the sub-surface 3300 NSv probe suffers a broken wire or loosens out of range, the transmitter drops the loop output below 3.6 mA within 100 µs. This immediate step prevents false alarms or high-scale vibration spikes in the host PLC/DCS. Furthermore, an onboard Power-up Inhibit circuit holds the loop output under 3.6 mA for 2 to 3 seconds after receiving power to suppress startup electrical spikes.

Frequently Asked Questions

Q: Can this transmitter be paired with a standard 3300 XL 8 mm proximity probe?

A: No. The Bently Nevada 990 transmitter is specifically tuned for the internal capacitance and narrow magnetic field characteristics of the 3300 NSv proximity probe system. Swapping in an 8 mm probe will disrupt system tuning and yield inaccurate data.

Q: How do technicians access dynamic raw waveform data for diagnostics?

A: The transmitter includes an ungrounded, non-isolated coaxial BNC connector labeled “PROX OUT.” Technicians can hook up portable vibration analyzers or oscilloscopes here to capture real-time orbit or time-waveform data without interrupting the main 4-20 mA control loop.

Field Installation Guidelines

• Secure the transmitter housing onto a flat machine plate or interior bulkhead using standard mounting screws according to the “-02” footprint.
• Next, ensure the system matches its specified length; this model requires a combined 5.0-metre electrical loop comprising the 3300 NSv probe and its extension cable.
• Subsequently, gap the proximity probe tip using a digital voltmeter across the terminal until the initial physical displacement sets the probe gap between 0.5 mm and 1.75 mm (20 to 55 mils) from the target surface.
• After that, route your 2-wire loop cables into the terminal block, verifying the external power supply delivers a clean +12 VDC to +35 VDC margin under load.
• Finally, utilize the non-interacting external zero and span adjustment potentiometers hidden beneath the transmitter protective label if the control loop requires manual trimming.