Bently Nevada 990 Vibration Transmitter
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  • Integrated Proximitor Sensor requires no external unit
  • Non-isolated “PROX OUT" and "COM" terminals plus a coaxial connector to provide a dynamic vibration and gap voltage signal output for diagnostics
  • Non-interacting zero and span potentiometers under the Transmitter label supports loop adjustment
  • Test Input pin for quick verification of loop signal output, using a function generator as the input
  • A Power-up Inhibit circuit eliminates signal errors due to line voltage transients
  • A Not OK/Signal Defeat circuit prevents high outputs or false alarms due to a faulty proximity probe or loose connection
  • Choice of DIN-rail clips or bulkhead mounting screws as standard options simplifies mounting
  • Potted construction for high humidity (up to 100% condensing) environments
  • Compatibility with 3300 NSv proximity probe allows transducer installation in small areas with minimal clearance, typical of centrifugal air compressors

The Bently Nevada 990 Vibration Transmitter is intended primarily for the original equipment manufacturers (OEMs) of centrifugal air compressors or small pumps, motors, or fans who prefer to provide a simple 4 to 20 mA proportional vibration signal as the input to their machinery control system.

The 990 vibration transmitter is a 2-wire, loop-powered device that accepts input from Bently Nevada's 3300 NSv proximity probes and a matching extension cable (available in 5 m and 7 m system length options). The transmitter conditions the signal into appropriate peak-to-peak vibration amplitude engineering units, and provides this value as a proportional 4 to 20 mA industry-standard signal as the input to the control system where machinery protection alarming and logic occurs.

Bently Nevada 990 Vibration Transmitter Specifications
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 4-20 mA
Loop Accuracy Within ±1.5% over specified full-scale range
Probe Gap Probe must be gapped between 0.5 and 1.75 mm from target to ensure full scale range
Maximum Loop Resistance 1,000 Ω including cable at 35 Vdc
Current Limiting 23 mA typical
Zero and Span Non-interacting external adjustments
NOT OK/Signal Defeat Signal output will go to less than 3.6 mA within 100 μs after a Not OK condition occurs. Signal output is restored within 2-3 seconds after the Not OK condition is removed
Power-up Inhibit Signal output stays at less than 3.6 mA for 2 to 3 seconds after power is applied
Proximitor Sensor Output Compatible with ungrounded, portable test equipment. When using grounded, ac-powered test equipment, use the 122115-01 Test Adapter for signal isolation
Output Impedance Prox Out has a 10 kΩ output impedance calibrated for a 10 MΩ load
Prox Out Linear Range 1.4 mm. Begins at approximately 0.25 mm from target surface
Prox Out Incremental Scale Factor 7.87 mV/μm (200 mV/mil) ± 6.5% typical including interchangeability errors when measured in increments of 0.25 mm over the linear range using a flat 30 mm target. Worst case 7.87 mV/μm ± 10%. Typical Noise Level: 50 mV/pp
Temperature Stability Incremental scale factor remains within ±10% of 7.87 mV/μm from 0 °C to +70 °C
Frequency Response 5 Hz to 6,000 Hz +0, -3 dB
Minimum Target Size 9.5 mm diameter
Leadwire Length Maximum for Proximitor Sensor Output (BNC connector), maximum cable distance is 3 meters
Electrical Classification General Purpose Approval by Canadian Standards Association (CSA/NRTL/C) in North America and by VDE in Europe. 990 has the CE mark for Europe

Required Components

These additional components are required for the operation of your product. We strongly advise you to purchase these components unless you already own them or own a suitable alternative.

Bently Nevada 3300 XL NSv Extension Cable
Extension cables for Bently Nevada 3300 XL NSv Transducer System
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In Stock


Please consider these optional accessories.

Bently Nevada 990/991 Test Adapter
Inverts and isolates the PROX OUT signal allowing connection to AC-powered diagnostic equipment
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In Stock
Bently Nevada Weatherproof Housing
NEMA 4 rated housing protects transmitters from the elements
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Bently Nevada Technical Training
Training and consulting for applications involving all facets of power generation, mechanical drives, and petro-chemical industries
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This product can be used in the following applications:

Part Number Price Available
Show Configuration
Full-scale Option
0-4 mils pp (1-100 mm pp)
System Length
5.0 meters (16.4 feet)
35 mm DIN rail clips
CSA Division 2
Call for pricing 2
Show Configuration
Full-scale Option
0-5 mils pp (1-125 mm pp)
System Length
5.0 meters (16.4 feet)
35 mm DIN rail clips
Call for pricing 2

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