Product Overview
The Bently Nevada 991-25-70-01-00 is a precision thrust transmitter designed for axial vibration monitoring in rotating machinery. This industrial automation module accepts a single 3300 NSv proximity probe and provides a 4-20 mA output proportional to shaft position. With a full-scale range of 25-0-25 mils and a system length of 7.0 meters, the 991-25-70-01-00 delivers reliable thrust measurement for turbine, compressor, and motor applications. Its fast Not OK/Signal Defeat feature ensures rapid fault detection, going below 3.6 mA within 100 µs of a fault condition.
Technical Specifications
Key performance parameters of the Bently Nevada 991-25-70-01-00:
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Output Signal: 4-20 mA, 2-wire configuration
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Power Supply: +12 to +35 Vdc at the transmitter terminal
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Loop Accuracy: ±1.5% over specified full scale (typical)
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Maximum Loop Resistance: 1,000 Ω including cable at 35 Vdc
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Current Limiting: 23 mA typical
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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
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Operating Temperature: -35°C to +85°C (-31°F to +185°F)
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Storage Temperature: -51°C to +100°C (-60°F to +212°F)
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Weight: 0.43 kg (0.9 lb)
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Mounting: 35 mm DIN-rail clips
Real-World Applications
The Bently Nevada 991-25-70-01-00 is ideal for axial position monitoring in steam turbines, centrifugal compressors, and large electric motors. In a typical turbine thrust bearing application, the transmitter detects minute shaft displacement and converts it to a linear 4-20 mA signal for PLC or DCS integration. Its rapid Not OK response protects against catastrophic bearing failure by alerting operators within microseconds of a fault condition. The 0.25 to 1.65 mm linear range ensures accurate measurements across the full operating envelope.
Installation Guide
Mount the Bently Nevada 991-25-70-01-00 on a standard 35 mm DIN rail using the provided clips. Connect the 3300 NSv proximity probe and extension cable to the input terminals. Wire the 4-20 mA loop in a 2-wire configuration, ensuring the total loop resistance does not exceed 1,000 Ω at 35 Vdc. Power the transmitter with +12 to +35 Vdc at the terminal block. Adjust zero and span using the non-interacting external potentiometers after installation. Verify the output at the desired full-scale range (e.g., 25-0-25 mils).
Maintenance Tips
Regularly inspect the proximity probe and cable for physical damage or contamination. Clean the probe face with a soft cloth and isopropyl alcohol if required. Check the transmitter’s operating temperature stays within -35°C to +85°C. Periodically verify the 4-20 mA loop accuracy using a calibrated multimeter. The Not OK self-test can be triggered by simulating a fault to confirm the output drops below 3.6 mA within 100 µs. Recalibrate zero and span if the reading drifts beyond ±1.5%.
Selection Guide & Purchasing Advice
Before purchasing the Bently Nevada 991-25-70-01-00, confirm your system length and full-scale range requirements. This model includes a 7.0-meter system length and 25-0-25 mils full-scale option. Ensure your control system accepts a 4-20 mA input with a maximum loop resistance of 1,000 Ω. For additional accessories or replacement units, contact ubest101 for competitive pricing and fast delivery.