Introduction to the 990-08-70-02-CN
When rotating machinery begins to vibrate excessively, the 990-08-70-02-CN from Bently Nevada provides a clear electrical signal that operators can trust. This 990 Vibration Transmitter accepts one non-contacting 3300 NSv Proximity Probe and extension cable. It converts the probe's dynamic motion into a standard 4-20 mA signal, making it straightforward to interface with existing control systems.
Designed for continuous operation, the transmitter requires a +12 to +35 Vdc input at the terminal. Its loop-powered design simplifies wiring, reducing installation complexity. With a full-scale option of 0-8 mils pp (0-200 μm pp), it suits applications where precise vibration measurement is critical.
This unit is manufactured in the U.S.A. and carries the CN approvals country-specific option, indicating it meets certain regional requirements. The 7.0-meter (23.0 feet) system length option provides flexibility for sensor placement.
Key Features and Technical Specifications
The 990-08-70-02-CN offers several features that make it a dependable choice for vibration monitoring. Its 4-20 mA output is proportional to the full-scale range, allowing direct connection to PLCs, DCSs, or standalone meters. The loop accuracy is within ±1.5% over the specified full-scale range, measured from the TEST signal input to the voltage across a 250 Ω loop resistance.
- Input: Accepts 1 non-contacting 3300 NSv Proximity Probe and extension cable.
- Power: Requires +12 to +35 Vdc input at the transmitter terminal.
- Signal Output: 4 to 20 mAdc over specified full-scale range in 2-wire configuration.
- Maximum Loop Resistance: 1,000 Ω including cable at 35 Vdc.
- Current Limiting: 23 mA typical.
- Frequency Response: 5 Hz to 6,000 Hz +0, 3 dB.
- Minimum Target Size: 9.5 mm (0.375 in) diameter.
- Probe Gap: Must be gapped between 0.5 and 1.75 mm (20 and 55 mils) from target.
One distinctive spec is the current limiting of 23 mA typical. This protects the loop from overcurrent conditions, enhancing reliability. Additionally, the signal output drops to less than 3.6 mA within 100 µs after a Not OK condition occurs, and restores within 2-3 seconds after the condition is removed. This fast response aids in fault detection.
Installation and Mounting
Mounting the 990-08-70-02-CN is straightforward with the bulkhead screw option (Mounting Option 02). This allows secure attachment to panels or enclosures. The transmitter's compact design and 0.43 kg (0.9 lbm) weight simplify handling during installation.
For proper operation, ensure the probe is gapped correctly (0.5 to 1.75 mm). The maximum leadwire length for the Proximitor Sensor Output (BNC connector) is 3 meters (10 feet). Keep cable runs within this limit to avoid signal degradation.
Power supply requirements are flexible: +12 to +35 Vdc. At 35 Vdc, the maximum loop resistance is 1,000 Ω, including cable. This allows for long cable runs in many industrial settings.
Maintenance and Reliability
From a maintenance engineer's perspective, the 990-08-70-02-CN is designed for minimal upkeep. The non-interacting external zero and span adjustments simplify calibration. Regular inspection of the probe gap and cable connections is recommended to ensure accurate readings.
The transmitter's fast Not OK response (less than 3.6 mA within 100 µs) helps identify faults quickly, reducing downtime. Its robust design, with a frequency response of 5 Hz to 6,000 Hz, covers most machinery vibration frequencies.
For long-term reliability, verify that the power supply remains within the specified range. Avoid exceeding the maximum loop resistance to maintain signal integrity.
Applications and Use Cases
The 990-08-70-02-CN is suitable for monitoring vibration on pumps, fans, compressors, and other rotating equipment. Its 4-20 mA output integrates easily with existing control systems, making it a practical choice for retrofits or new installations.
In a typical scenario, a maintenance team might install this transmitter on a critical pump. The 0-8 mils pp range provides adequate sensitivity for detecting early bearing wear. The 7.0-meter cable length allows the sensor to be placed near the bearing housing while the transmitter is mounted in a safe location.
For hazardous area locations (NonHazardous, Zone 2 or Div 2), the transmitter can operate with a 28 V power supply. This flexibility supports various site requirements.
Support and Availability
The 990-08-70-02-CN is available through AutoDCSTech. As an industrial automation parts supplier, AutoDCSTech can provide this vibration transmitter to support your machinery monitoring needs. Please verify current lifecycle status and availability with AutoDCSTech before ordering.
