Description

The Bently Nevada 990-05-50-01-CN is a loop-powered, 2-wire vibration transmitter designed primarily for industrial machinery protection loops. It integrates the essential signal processing functionality of a Proximitor sensor into a compact, field-mountable package that interfaces directly with a 3300 NSv proximity probe. It outputs a continuous 4-20 mA analog signal proportional to the relative vibration level, enabling direct integration into a PLC, DCS, or SCADA system without a specialized, rack-based monitor.

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 option.
• 50: 5.0 metres (16.4 feet) total electrical system length.
• 01: 35 mm DIN rail clips mounting configuration.
• CN: Regional hazardous area approval compliance (including Chinese NEPSI standards).

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: What distinct advantage does the “-CN” suffix provide?

A: The “-CN” option specifies that the transmitter meets local hazardous area standards, notably including NEPSI (National Supervision and Inspection Centre for Explosion Protection and Safety of Instrumentation) certifications for China. This ensures regulatory compliance when installed in restricted or hazardous environments.

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.

Field Installation Guidelines

• Snap the transmitter housing securely onto a standard 35 mm DIN rail inside your local junction box using the integrated “-01” mounting clips.
• 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.