Product Overview
The Bently Nevada 990-08-70-02-00 is a precision 990 Vibration Transmitter designed for continuous monitoring of machinery vibration. It accepts input from one non-contacting 3300 NSv Proximity Probe and extension cable, converting shaft displacement into a 4-20 mA signal over a full-scale range of 0-8 mils peak-to-peak (0-200 μm pp). This robust transmitter requires +12 to +35 Vdc power at the terminal and offers a maximum loop resistance of 1,000 Ω at 35 Vdc. By providing early warning of abnormal vibration, the 990-08-70-02-00 helps prevent costly equipment failures and unscheduled downtime, delivering tangible return on investment through extended machinery life.
Technical Specifications
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Input: Accepts 1 non-contacting 3300 NSv Proximity Probe and extension cable
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Power Requirement: +12 to +35 Vdc at transmitter terminal
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Output: 4-20 mAdc over specified full-scale range (2-wire configuration)
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Accuracy: Within ±1.5% over specified full-scale range (tested across 250 Ω)
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Loop Resistance: Maximum 1,000 Ω including cable at 35 Vdc
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Current Limiting: 23 mA typical
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Frequency Response: 5 Hz to 6,000 Hz +0, -3 dB
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Probe Gap: 0.5 to 1.75 mm (20-55 mils) from target
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Minimum Target Size: 9.5 mm (0.375 in) diameter
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Signal Defeat: Output goes below 3.6 mA within 100 μs on NOT OK, recovers in 2-3 seconds
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Weight: 0.43 kg (0.9 lbm)
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Mounting: Bulkhead screws (Option 02)
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Agency: Hazardous area capable: Non-Hazardous, Zone 2, or Div 2 (Power Supply: 28 V)
Real-World Applications
The 990-08-70-02-00 excels in monitoring critical rotating assets such as compressors, turbines, pumps, and fans. In a petrochemical plant, continuous vibration tracking from this transmitter enables predictive maintenance, reducing unplanned shutdowns by 30% or more. For power generation facilities, the 4-20 mA loop output integrates seamlessly with existing DCS or PLC systems, providing reliable data for early fault detection. The cost savings from avoiding catastrophic bearing failures far outweigh the initial investment in this Bently Nevada 990-08-70-02-00.
Installation Guide
Proper installation ensures optimal performance. Mount the transmitter using bulkhead screws (included with Option 02). Connect a 3300 NSv probe and extension cable; ensure the probe gap is set between 0.5 and 1.75 mm from the target. Power the unit with +12 to +35 Vdc at the terminal, and connect the 4-20 mA loop across a maximum 1,000 Ω resistor. For Proximitor Sensor Output via BNC, keep cable distance under 3 meters (10 feet). Non-interacting zero and span adjustments allow easy calibration without powering down the loop.
Maintenance & Reliability
Routine inspection intervals should follow OEM recommendations—typically every 6-12 months. Check probe clearance, cable integrity, and loop voltage. The 990-08-70-02-00's current-limiting feature (23 mA typical) protects against loop faults. With no moving parts and proven Bently Nevada design, this transmitter offers long service life, minimizing total cost of ownership. Periodic verification of the 4-20 mA output against a known vibration source ensures sustained accuracy.
Troubleshooting Common Issues
If the signal output drops below 3.6 mA, a NOT OK condition has occurred—check probe gap, cable connections, and power supply. The unit recovers within 2-3 seconds after the fault clears. For inaccurate readings, verify the probe gap is within 0.5-1.75 mm and that the target meets the minimum 9.5 mm diameter requirement. Ensure loop resistance does not exceed 1,000 Ω. If zero and span drift, use the non-interacting external adjustments to recalibrate. For additional support, contact ubest101—your trusted source for industrial automation spares.