990-08-50-03-CN Vibration Transmitter Overview
When machine vibration threatens uptime, the 990-08-50-03-CN from Bently Nevada provides a direct, loop-powered solution. This 990 Vibration Transmitter accepts one non-contacting 3300 NSv Proximity Probe and extension cable, converting dynamic shaft vibration into a standard 4-20 mA signal. With a full-scale range of 0-8 mils pp (0-200 μm pp), it suits a wide variety of rotating machinery monitoring tasks.
The transmitter operates on +12 to +35 Vdc input at the terminal, and its 4-20 mA output is proportional to the measured vibration. Designed for industrial environments, it offers a maximum loop resistance of 1,000 Ω including cable at 35 Vdc, ensuring compatibility with most control systems. Its compact, DIN-clip mounting simplifies installation in existing panels.
Key Features and Technical Specifications
- Full-scale range: 0-8 mils pp (0-200 μm pp) – option 08
- System length: 5.0 meters (16.4 feet) – option 50
- Mounting: DIN clips and screws – option 03
- Input: Accepts 1 non-contacting 3300 NSv Proximity Probe and extension cable
- Power: Requires +12 to +35 Vdc input at the transmitter terminal
- Maximum loop resistance: 1,000 Ω including cable at 35 Vdc
- Current limiting: 23 mA typical
- Signal output: 4-20 mAdc over specified full-scale range in 2-wire configuration
- Loop accuracy: Within ±1.5% over specified full-scale range (from TEST signal to voltage across 250 Ω loop resistance)
- Probe gap: Must be gapped between 0.5 and 1.75 mm (20 and 55 mils) from target
- NOT OK/signal defeat: Output goes to less than 3.6 mA within 100 µs after Not OK condition; restored within 2-3 seconds after removal
- Frequency response: 5 Hz to 6,000 Hz +0, 3 dB
- Minimum target size: 9.5 mm (0.375 in) diameter
- Leadwire length: Maximum 3 meters (10 feet) for Proximitor Sensor Output (BNC connector)
- Hazardous area: Non-Hazardous, Zone 2 or Div 2; Power Supply: 28 V
One distinctive feature is the NOT OK/signal defeat function. When a fault occurs, the output drops below 3.6 mA within 100 µs, providing a clear, fast indication to the control system. This rapid response helps prevent undetected sensor failures, enhancing overall system reliability.
Comparison with Similar Vibration Transmitters
Compared to standard 4-20 mA vibration transmitters, the 990-08-50-03-CN offers a wider input voltage range (+12 to +35 Vdc) and a higher maximum loop resistance (1,000 Ω), making it more flexible for various loop configurations. Its frequency response of 5 Hz to 6,000 Hz covers typical machine vibration frequencies, while the 0-8 mils pp range is suitable for many rotating assets. The built-in NOT OK signal defeat is a safety feature not found on all transmitters, providing an extra layer of diagnostic capability.
Installation and Setup
Mount the 990-08-50-03-CN using the provided DIN clips and screws. Ensure the proximity probe is correctly gapped between 0.5 and 1.75 mm (20 and 55 mils) from the target to achieve full-scale range. Connect the probe and extension cable to the transmitter input. Wire the transmitter in a 2-wire configuration, supplying +12 to +35 Vdc at the terminal. Verify that the total loop resistance, including cable, does not exceed 1,000 Ω at 35 Vdc. After power-up, check the 4-20 mA output corresponds to the measured vibration.
Maintenance and Reliability
Regularly inspect the probe gap and cable connections to ensure accurate readings. Periodically verify the transmitter's output against a known vibration source. The NOT OK function will alert you to any internal fault, allowing prompt troubleshooting. For hazardous area installations (Zone 2 or Div 2), follow the manufacturer's safety manual and local regulations. Routine checks help maintain long-term reliability and prevent unexpected downtime.
Troubleshooting Common Issues
If the output remains below 3.6 mA, the transmitter may be in a NOT OK state. Check the probe gap, cable integrity, and power supply. If the output is inaccurate, verify the loop resistance and calibration. Ensure the probe is correctly positioned within the specified gap range. For persistent issues, consult the Bently Nevada manual or contact AutoDCSTech for support.
Product Support and Availability
The Bently Nevada 990-08-50-03-CN is available through AutoDCSTech. Contact us for current availability and lead times. We are an industrial automation parts supplier dedicated to helping you maintain your machinery monitoring systems.
