Why Accurate Thrust Monitoring Matters
When rotating machinery experiences unexpected axial thrust, the consequences can be severe. Bearing wear, shaft damage, and unplanned downtime often follow. The 991-25-50-03-01 from Bently Nevada provides a reliable solution for continuous axial position monitoring. This probe vibration transmitter converts proximity probe signals into a standard 4-20 mA output, enabling seamless integration with control systems.
What Is the 991-25-50-03-01?
The 991-25-50-03-01 is a thrust transmitter designed for axial measurement applications. It operates with a single non-contacting 3300 NSv proximity probe and extension cable. The transmitter is housed in a DIN rail mountable enclosure, making installation straightforward in existing panels. With a full-scale range of 25-0-25 mils, it suits many turbomachinery and compressor applications.
Key Features & Technical Specifications
- Output Signal: 4-20 mA DC in a two-wire configuration
- Power Requirement: +12 to +35 Vdc input at the transmitter terminal
- Linear Range: 0.25 to 1.65 mm for Prox Out; suitable for 0.6-0-0.6 mm or 25-0-25 mils current loop linear ranges
- Maximum Loop Resistance: 1,000 Ω including cable at 35 Vdc
- Current Limiting: 23 mA typical
- Zero and Span: Non-interacting external adjustments
- Not OK/Signal Defeat: Output goes below 3.6 mA within 100 µs after a Not OK condition; restored within 0.1 seconds after removal
- Environmental Limits: Operating temperature -35°C to +85°C; storage temperature -51°C to +100°C
- Weight: 0.43 kg (0.9 lbm)
- Agency Approval: CSA Division 2
Performance Metrics
The 991-25-50-03-01 delivers 4-20 mA loop accuracy within ±1.5% over the specified full-scale range. This accuracy is rated from the TEST signal input to the voltage measured across a 250 Ω loop resistance. Such precision ensures reliable data for condition monitoring and protection systems.
Installation & Setup
Mounting the 991-25-50-03-01 is simple. It uses DIN clips and screws, fitting onto a standard DIN rail. The system length option of 5.0 meters (16.4 feet) provides flexibility in probe placement. Wiring follows a two-wire loop configuration, simplifying connections to PLCs, DCS, or standalone indicators.
Maintenance & Reliability
Routine inspection is essential for long-term reliability. Check the transmitter and probe connections periodically. Verify the output signal responds correctly to simulated or actual thrust changes. Follow the manufacturer's manual for any maintenance procedures. The robust design operates reliably across a wide temperature range, reducing the need for frequent servicing.
Compatibility & Integration
This transmitter works with Bently Nevada's 3300 NSv proximity probe system. Its 4-20 mA output interfaces with most industrial control systems, including PLCs and DCS. The CSA Division 2 approval makes it suitable for hazardous locations, expanding its application scope.
Troubleshooting Common Issues
If the output signal is not within expected range, first verify the power supply voltage. Ensure it is between +12 and +35 Vdc. Next, check the loop resistance; it must not exceed 1,000 Ω. If a Not OK condition occurs, the output drops below 3.6 mA, signaling a fault. The transmitter recovers automatically within 0.1 seconds after the fault clears.
Product Support & Availability
The 991-25-50-03-01 is available through AutoDCSTech. Our team provides technical support and fast shipping. Contact us to verify current lifecycle status and availability before ordering.
