The 991-25-50-01-05 is a 2-wire, loop-powered axial displacement transmitter featuring a 25-0-25 mils full-scale range and a 5.0-meter system configuration. Integrated with an on-board Proximitor sensor inside a rugged, potted enclosure with 35mm DIN-rail mount clips, this unit works seamlessly with industrial PLCs and control systems to deliver a proportional 4 to 20 mA signal and comprehensive multi-agency hazardous area protection without requiring a separate signal conditioner.

Features and benefits

Integrated Proximitor Sensor – No external unit required, simplifying installation.

4–20 mA Output – Provides standard proportional axial displacement signal for control systems.

Diagnostic Terminals – PROX OUT and coaxial connector enable vibration and gap monitoring.

Loop Adjustment – Non-interacting zero and span potentiometers support easy calibration.

Robust Construction – Potted design ensures reliable operation in high-humidity environments.

Flexible Mounting – DIN-rail clips or bulkhead screws for versatile installation.

Specific Application

• Axial displacement (thrust position) trending and machine protection loops inside centrifugal air compressors, small pumps, industrial motors, or fans.
• Compact control cabinet integration where multi-sensor loops require a simple 4 to 20 mA analog signal directed straight to a localized PLC or DCS system.
• High-humidity or condensing field conditions requiring a fully potted transmitter capable of maintaining structural loop integrity up to 100% relative humidity.

System Compatibility, Alternative Models, and Differences

• System Compatibility:
  Fully compatible with the Bently Nevada 3300 NSv proximity probe series and matching 330930 unarmored or armored extension cables tuned for a 5.0-meter total loop system length. It interfaces directly with standard 2-wire control loops requiring 17 to 35 VDC loop power and outputs a proportional 4 to 20 mA signal to industrial processors.
• Alternative Model (Metric Series / Different Mount Variant):
  991-06-70-02-05 (0.6-0-0.6 mm Metric Range, 7.0m System Length, Bulkhead Mount)
• Key Differences between 991-25-50-01-05 and 991-06-70-02-05:

Engineering Measurement Scale: The 991-25-50-01-05 features an English scale calibration of 25-0-25 mils, whereas the alternative model utilizes a metric scale calibration of 0.6-0-0.6 mm.

Transducer Tuning System Length: The 991-25-50-01-05 is specifically tuned for a shorter 5.0-meter probe and cable combination, while the alternative uses a 7.0-meter total length adjustment.

Mechanical Hardware Mounting Base: The 991-25-50-01-05 is supplied with standard 35mm DIN-rail mounting clips, whereas the alternative model incorporates raw bulkhead mounting holes and 6-32 machine screws for surface installations.

Ordering Information

FAQ

Q1: What type of signal does the 991 Thrust Transmitter provide?
A1: It provides a 4–20 mA proportional axial displacement (thrust) signal for machinery control systems.

Q2: Which proximity probe is compatible with this transmitter?
A2: The 991 is compatible with the Bently Nevada 3300 NSv proximity probe.

Q3: How is the transmitter powered?
A3: It is a 2-wire, loop-powered device, requiring no separate power supply.

Q4: Can it operate in high-humidity environments?
A4: Yes, the potted construction allows operation in 100% condensing humidity.

Q5: What mounting options are available?
A5: It supports DIN-rail clips or bulkhead mounting screws for flexible installation.

Accessories