Bently Nevada 991 Thrust Transmitter

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

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