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

• Detects rotor malfunctions such as unbalance and misalignment early.

• Captures vibration amplitudes and frequencies from fan motors and speed reducers.

• Ensures effective machine protection when properly mounted on the casing.

• Reduces false signals with correct installation on bearing housing or machine casing.

• Supports engineering guidance for optimal measurement and 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 is the primary purpose of the 190501-12-00-02?
A1: It measures low-frequency casing vibration velocity on cooling tower and air-cooled heat-exchanger fan assemblies.

Q2: What operating speed range is suitable for this transducer?
A2: It is designed for fans operating at or above 90 rpm, typically 100–300 rpm.

Q3: Can it detect machine faults?
A3: Yes, it identifies common rotor issues like unbalance and misalignment through vibration changes.

Q4: Where should the transducer be installed?
A4: It should be mounted on the bearing housing or machine casing to ensure accurate readings.

Q5: Does Bently Nevada provide installation support?
A5: Yes, engineering services are available to determine proper mounting and measurement locations.

Accessories

Spare Mounting Adapters

All mounting adapters are made from 300 series stainless steel.

Standard Studs

Hex Plate Studs

Quick Disconnect Components

The following three components are included with the quick disconnect mounting option for the Velomitor CT Transducer. The quick disconnect option allows you to remove the transducer without rotating it, allowing you to keep the cable connected to the transducer.

Fittings

Conduit fittings allow connection of flexible, metal, liquid-tight conduit or armor to the conduit adapter.