Bently Nevada：991-01-XX-01-00

Description 

The 991 Thrust 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 axial displacement (thrust) signal as the input to their machinery control system. The transmitter is a 2-wire, loop-powered device that accepts input from our 3300 NSv* proximity probe and its matching extension cable (available in 5 m and 7 m system length options). The transmitter conditions the signal into appropriate engineering units proportional to the shaft’s axial position1, 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.

The 991 transmitter provides the following notable 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 diagnostics3. 

• 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.

Ordering Information

991-AXX-BXX-CXX-DXX 

A: Full-scale Option

 0 6 0.6 -0- 0.6 mm 

 2 5 25-0-25 mils 

B: System Length Option 

5 0 5.0 metres (16.4 feet) 

7 0 7.0 metres (23.0 feet) 

C: Mounting Option 

0 1 35 mm DIN-rail clips 

0 2 Bulkhead screws 

0 3 DIN clips and screws 

D: Agency Approval Option 

0 0 Not required 

0 1 CSA Division 2 

0 5 CSA Division 2, ATEX Zone 0, ATEX Zone 2 and includes ABS maritime approval