Product Overview
When monitoring axial shaft position in critical rotating machinery, signal reliability is paramount. The Bently Nevada 991-25-70-03-05 Probe Vibration Transmitter provides a robust solution for detecting thrust position with a 4-20 mA output. Designed for use with a non-contacting 3300 NSv proximity probe, this DIN rail-mounted transmitter delivers accurate, real-time data for predictive maintenance and asset protection. The 991-25-70-03-05 is built to withstand harsh environments, with agency approvals including CSA Division 2, ATEX Zone 0, ATEX Zone 2, and ABS maritime approval.
Technical Specifications
The Bently Nevada 991-25-70-03-05 offers precise linear range options and environmental resilience. Key parameters include:
| Parameter |
Value |
| Input |
Accepts 1 non-contacting 3300 NSv Proximity Probe and extension cable |
| Power |
Requires +12 to +35 Vdc input at the transmitter terminal |
| Output Signal |
4 to 20 mAdc over specified full-scale range (2-wire) |
| Loop Accuracy |
Within ±1.5% over specified full scale range (typical) |
| Maximum Loop Resistance |
1,000 Ω including cable at 35 Vdc |
| Current Limiting |
23 mA typical |
| Linear Range |
0.25 to 1.65 mm for Prox Out; suitable for 25-0-25 mils current loop linear ranges |
| Operating Temperature |
-35°C to +85°C (-31°F to +185°F) |
| Storage Temperature |
-51°C to +100°C (-60°F to +212°F) |
| Weight |
0.43 kg (0.9 lbm) |
Industrial Applications
The Bently Nevada 991-25-70-03-05 is specifically designed for axial thrust monitoring in turbomachinery, compressors, and large rotating equipment. In a failure mode scenario, the transmitter's Not OK/Signal Defeat feature quickly brings the output below 3.6 mA within 100 µs, alerting the control system to a probe fault or signal loss. This fast response prevents costly damage and unplanned downtime. Typical applications include steam turbines, centrifugal compressors, and hydroelectric generators where precise axial position control is critical.
Installation & Setup
Mount the Bently Nevada 991-25-70-03-05 on a standard DIN rail using the supplied DIN clips and screws (Mounting Option 03). Connect the 3300 NSv proximity probe and extension cable (7.0 meters system length as per -70 option). Wire the transmitter in a 2-wire configuration, ensuring the loop resistance does not exceed 1,000 Ω. The non-interacting external adjustments allow independent zero and span calibration. Verify the linear range settings match the probe's gap voltage requirements for 25-0-25 mils or 0.6-0-0.6 mm range.
Maintenance & Reliability
To ensure long-term reliability, inspect the probe tip and cable for wear or contamination every six months. The Bently Nevada 991-25-70-03-05 operates reliably in extreme temperatures from -35°C to +85°C. Its current limiting (23 mA typical) protects the loop from overcurrent conditions. Routine calibration checks using the TEST signal input help maintain the ±1.5% accuracy specification. By preventing undetected thrust misalignment, this transmitter reduces the risk of bearing failure and extends machinery life.
Selection Guide
When ordering the Bently Nevada 991-25-70-03-05, verify the full-scale option (-25 for 25-0-25 mils) and system length (-70 for 7.0 meters). The agency approval option 05 includes CSA Division 2, ATEX Zone 0, ATEX Zone 2, and ABS maritime approval, making it suitable for offshore and hazardous environments. For additional support, contact a reliable supplier like ubest101 to confirm compatibility with your existing 3300 NSv probe and extension cable.