Bently Nevada 990-08-70-02-CN 990 Vibration Transmitter

990 Vibration Transmitter 990-08-70-02-CN

Product Introduction

The Bently Nevada 990-08-70-02-CN is a compact, loop-powered 2-wire vibration transmitter engineered for continuous machinery monitoring. It accepts input from one non-contacting 3300 NSv proximity probe and an extension cable, converting shaft vibration into a proportional 4-20 mA signal. This model offers a full-scale range of 0-8 mils pp (0-200 μm pp) and a system length of 7.0 meters (23.0 feet) . Its bulkhead screw mounting option simplifies installation in tight panels, while the country-specific approval (CN) ensures compliance with regional standards. For plant operators seeking reliable, cost-effective vibration monitoring, the 990-08-70-02-CN delivers consistent performance in both non-hazardous and Zone 2/Div 2 hazardous locations.

Electrical and Input Specifications

This transmitter requires a +12 to +35 Vdc power supply at its terminal block, making it compatible with most industrial DC systems. It produces a 4 to 20 mAdc signal over the specified full-scale range using a 2-wire configuration. The loop accuracy is rated at ±1.5% when measured from the TEST signal input across a 250 Ω load resistor. Notably, this error is additive to the Prox Out Incremental Scale Factor. The maximum loop resistance is 1,000 Ω including cable at 35 Vdc, and the current limiting is typically 23 mA. Additionally, the zero and span adjustments are non-interacting external potentiometers, allowing for convenient field calibration without affecting each other.

Probe Setup and Frequency Response

For proper operation, the connected proximity probe must be gapped between 0.5 and 1.75 mm (20 to 55 mils) from the target to achieve the full-scale range. The transmitter's frequency response spans from 5 Hz to 6,000 Hz (+0, -3 dB), covering common machine vibration frequencies. The minimum target size required is 9.5 mm (0.375 in) in diameter. Furthermore, the leadwire length between the Proximitor Sensor Output (BNC connector) and the transmitter should not exceed 3 meters (10 feet) for optimal signal integrity. This configuration ensures accurate vibration data acquisition for turbines, compressors, and pumps.

Not OK and Safety Features

A critical feature of the Bently Nevada 990-08-70-02-CN is its NOT OK/signal defeat function. The signal output drops to less than 3.6 mA within 100 µs after a NOT OK condition occurs, alerting the control system to a fault. Once the condition clears, the output restores within 2-3 seconds automatically. This rapid response enhances system reliability and prevents false machinery trips. The unit is approved for non-hazardous, Zone 2, or Division 2 hazardous area locations when powered with a 28 V supply. Its rugged design and country-specific approvals make it a versatile choice for international projects.

Installation and Mounting Guidance

Mounting the 990-08-70-02-CN is straightforward using the bulkhead screws provided with the 02 mounting option. First, secure the transmitter housing to a flat panel surface using the two screws. Next, connect the 3300 NSv probe and extension cable to the input terminals, ensuring the probe gap is within the 0.5 to 1.75 mm range. Then, wire the power supply (+12 to +35 Vdc) to the terminal block, observing correct polarity. For loop connections, keep the total resistance below 1,000 Ω at 35 Vdc to maintain accurate 4-20 mA transmission. Finally, use the non-interacting zero and span pots to calibrate the output to match your monitoring system.

Packaging and Shipping

Each 990-08-70-02-CN unit comes securely packaged in anti-static foam within a sturdy cardboard box. The package contains the vibration transmitter assembly, two bulkhead mounting screws, and a quick-start wiring diagram. The net weight is 0.43 kg (0.9 lbm) , while the gross weight for shipping is 0.65 kg including packaging materials. All orders are dispatched via FedEx, UPS, or DHL with real-time tracking available. Please be aware that this listing excludes calibration certificates and any warranty documentation.

Frequently Asked Questions (FAQ)

1. Can I use this transmitter with any proximity probe?
No, the 990-08-70-02-CN is specifically designed to work with a non-contacting 3300 NSv proximity probe and its matching extension cable.

2. What happens if the probe gap falls outside 0.5-1.75 mm?
If the gap is outside this range, the transmitter may not output the correct 4-20 mA signal corresponding to the full-scale vibration range.

3. How do I adjust the zero and span?
Use the two non-interacting external potentiometers on the transmitter housing; turning one does not affect the other, simplifying calibration.

4. Is this transmitter approved for use in explosive environments?
Yes, the 990-08-70-02-CN is rated for non-hazardous, Zone 2, and Div 2 hazardous locations with a 28 V power supply.

5. What is the maximum cable length to the Proximitor output?
Keep the cable between the BNC connector and the transmitter under 3 meters (10 feet) to avoid signal degradation.