Bently Nevada 991 Thrust Transmitter

Name: Bently Nevada 991 Thrust Transmitter
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Provides a 4-20 mA signal proportional to thrust position on smaller, non-critical machinery.

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By Bently Nevada

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Product Specs

Features

Integrated Proximitor Sensor requires no external unit
Non-isolated “PROX OUT " and "COM" terminals plus a coaxial connector 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 allows quick verification of loop signal output, using a variable DC voltage source 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 991 Thrust Transmitter provides a 4-20 mA signal proportional to thrust position and is designed for use on smaller, non-critical machinery. Its primary use is on centrifugal air compressors with fluid-film thrust bearings. The 991 Thrust Transmitter can measure up to 1.2 mm or 50 mils of total thrust movement.

The 991 thrust transmitter is a 2-wire, loop-powered device that accepts input from Bently Nevada's 3300 NSv proximity probes and matching extension cables (available in 5 and 7 meter system length options). The transmitter conditions the signal into appropriate engineering units proportional to the shaft's axial position, and provides it as a 4 to 20 mA industry-standard signal for input to the control system where machinery protection alarming and logic occurs.

Bently Nevada 991 Thrust 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 to 20 mAdc over specified full-scale range in 2-wire configuration
Loop Accuracy	Within ±1.5% over specified 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 0.1 seconds after the Not OK condition is removed
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
Linear Range	0.25 to 1.65 mm for Prox Out. Suitable for 0.6-0-0.6 mm or 25-0-25 mils current loop linear ranges
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
Temperature Stability	Incremental scale factor remains within ±10% of 7.87 mV/μm from 0 °C to +70 °C
Minimum Target Size	9.5 mm diameter
Leadwire Length	Maximum for Proximitor Sensor Output (BNC connector), maximum cable distance is 3 meters
Non-Hazardous, Zone 2 or Div 2 Hazardous area locations	13 km (8 miles) maximum between transmitter and receiving device for signal output
Intrinsically Safe Hazardous area locations	68 meters (225 ft.) maximum between transmitter and receiving device for signal output
Electrical Classification	General Purpose Approval by Canadian Standards Association (CSA/NRTL/C) in North America and by VDE in Europe. The 991 has the CE mark for Europe