Bently Nevada 991 Thrust Transmitter
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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 |
