990-08-50-02-CN Vibration Transmitter Overview
When machinery vibration threatens uptime, the 990-08-50-02-CN from Bently Nevada provides a dependable monitoring solution. This 990 Vibration Transmitter accepts one non-contacting 3300 NSv Proximity Probe and extension cable, converting dynamic vibration into a standard 4-20 mA signal. Designed for continuous operation, it helps maintenance teams detect developing faults before they cause costly failures.
With a full-scale range of 0-8 mils pp (0-200 μm pp), the 990-08-50-02-CN covers typical shaft vibration measurements in rotating machinery. The transmitter requires +12 to +35 Vdc input at the terminal, making it compatible with many industrial power supplies. Its compact, rugged enclosure suits installation in non-hazardous, Zone 2, or Div 2 hazardous area locations, with a 28 V power supply option.
Key Features and Technical Specifications
The 990-08-50-02-CN includes several features that simplify integration and improve reliability:
- Accepts one 3300 NSv proximity probe and extension cable for direct vibration sensing.
- Provides a 4-20 mA dc output over the specified full-scale range in a 2-wire configuration.
- Offers loop accuracy within ±1.5% over the full-scale range, measured from the TEST signal input to the voltage across a 250 Ω loop resistance.
- Includes non-interacting external zero and span adjustments for easy calibration.
- Features NOT OK/signal defeat: output drops to less than 3.6 mA within 100 µs after a fault, restoring within 2-3 seconds after removal.
- Frequency response of 5 Hz to 6,000 Hz (+0, 3 dB) captures relevant vibration components.
- Maximum loop resistance is 1,000 Ω including cable at 35 Vdc, with current limiting at 23 mA typical.
These specifications ensure accurate, repeatable vibration data for condition monitoring and protection systems.
Comparison with Similar Vibration Transmitters
Compared to other 2-wire vibration transmitters, the 990-08-50-02-CN stands out for its high accuracy and fast response. Many general-purpose transmitters offer ±5% accuracy, while this unit maintains ±1.5%. Its 100 µs NOT OK response is significantly faster than typical 1-second delays, enabling quicker trip actions. Additionally, the 5 Hz to 6 kHz frequency range covers both low-speed and high-speed machinery, whereas some models only handle 10 Hz to 1 kHz. These differences make the Bently Nevada unit a preferred choice for critical assets.
Installation and Setup Guidance
Proper installation is essential for optimal performance. The probe must be gapped between 0.5 and 1.75 mm (20 and 55 mils) from the target to ensure full-scale range. Use the supplied bulkhead screws (mounting option 02) for secure attachment. The system length option of 5.0 meters (16.4 feet) defines the cable run between probe and transmitter. For the Proximitor Sensor Output (BNC connector), maximum cable distance is 3 meters (10 feet). Ensure the power supply provides +12 to +35 Vdc at the transmitter terminal, and verify loop resistance does not exceed 1,000 Ω at 35 Vdc.
Maintenance and Reliability Tips
Regular inspection of the probe gap and cable connections helps maintain measurement integrity. Because the transmitter is solid-state, it requires minimal routine care. Periodically verify the 4-20 mA loop accuracy by injecting a test signal and measuring across a 250 Ω resistor. Keep the unit within its specified environmental limits to avoid drift. Following the manufacturer's manual ensures long-term reliability and reduces unplanned downtime.
Compatibility and Integration
The 990-08-50-02-CN integrates seamlessly with existing Bently Nevada monitoring systems and any PLC, DCS, or SCADA that accepts 4-20 mA inputs. Its 2-wire configuration simplifies wiring, and the non-interacting zero and span adjustments allow field calibration without special tools. The transmitter works with standard 3300 NSv proximity probes, ensuring compatibility with many installed assets.
Common Issues and Troubleshooting
If the output signal is missing or erratic, check the power supply voltage at the transmitter terminal—it must be between +12 and +35 Vdc. Verify that the probe gap is within 0.5 to 1.75 mm; an incorrect gap can cause non-linearity or loss of signal. If the output stays below 3.6 mA, a NOT OK condition may be present; inspect the probe and cable for damage. Ensure loop resistance is below 1,000 Ω to avoid voltage drop issues. For persistent problems, consult the Bently Nevada manual or contact AutoDCSTech.
Product Support and Availability
The 990-08-50-02-CN is available through AutoDCSTech, a trusted supplier of industrial automation parts. In stock and ready to ship, this transmitter helps you maintain reliable vibration monitoring. Contact AutoDCSTech for current lifecycle status and availability before ordering.
