Description

The Bently Nevada 990-08-XX-01-00 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.

The “XX” in this part number indicates a variable option placeholder for the total electrical system length, typically designated as either 50 (5.0 metres) or 70 (7.0 metres).

Suffix Part Number Breakdown

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

• 990: Base Model Number for the 990 Vibration Transmitter.
• 08: 0–8 mils peak-to-peak (0–200 µm pp) full-scale range option.
• XX: System Length Option placeholder (50 = 5.0 metres / 70 = 7.0 metres total length).
• 01: 35 mm DIN rail clips mounting configuration.
• 00: No specialized regional agency approvals required (Standard configuration).

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: How does the “08” option alter the scale factor compared to a standard “05” option?

A: The “08” option expands the full-scale measuring window to 0-8 mils peak-to-peak (200 µm pp) compared to the standard 0-5 mils span. This allows the host control loop to monitor higher mechanical vibration amplitudes on heavier machinery before capping or clipping the current loop output.

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 loop matches its specified length; your specific configuration will require either a combined 5.0-metre or 7.0-metre electrical loop depending on what variant fills the XX placeholder.
• 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.