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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


In Stock

Part Number System Length Mounting Approvals Price Available
5.0 meters (16.4 feet)
35 mm DIN rail clips
CSA Division 2, ATEX Zone 0, ATEX Zone 2, ABS maritime approval
Call for pricing 5 in stock
7.0 meters (23.0 feet)
Bulkhead screws
Call for pricing 1 in stock

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