Bently Nevada 991-25-70-01-01 Thrust Transmitter | 4-20mA

Product Overview

The Bently Nevada 991-25-70-01-01 991 Series Probe Vibration Transmitter delivers reliable, continuous measurement of axial shaft position in critical rotating machinery. Designed specifically for industrial automation environments, this 2-wire loop-powered unit translates non-contacting proximity probe inputs into a standard industrial control signal. Engineered and manufactured in the United States, the unit guarantees high operational integrity for machinery protection systems.

Technical Specifications & MECE Classification

• Brand & Model: Bently Nevada 991-25-70-01-01 (991 Series)
• Measurement Range & Linear Range: Full-scale option features 25-0-25 mils, supporting linear ranges of 0.6-0-0.6 mm or 25-0-25 mils with a linear range of 0.25 to 1.65 mm for Prox Out.
• Sensitivity & Accuracy: 4 to 20 mA loop accuracy remains within plus or minus 1.5% over the specified full-scale range under typical operating conditions.
• Frequency Response & Signal Characteristics: Current limiting is set at 23 mA typical with a maximum loop resistance of 1,000 ohms at 35 Vdc. The unit features non-interacting external zero and span adjustments.
• Resolution & Diagnostics: Not OK/Signal Defeat logic drops output below 3.6 mA within 100 microseconds during fault conditions and restores output within 0.1 seconds after fault removal.
• Temperature Range & Environmental Tolerances: Transmitter operating temperature spans from minus 35 degrees Celsius to plus 85 degrees Celsius, while storage temperature ranges from minus 51 degrees Celsius to plus 100 degrees Celsius.
• Interference Immunity & Power: Requires plus 12 to plus 35 Vdc input power at the transmitter terminal in a 2-wire configuration.
• Physical & Mechanical Parameters: Weighs 0.43 kg (0.9 lbm). Features Polyphenylene sulfide transducer tip material, AISI 303 or 304 stainless steel case, and a 75-ohm coaxial probe cable.

Installation & Commissioning Guide

• Secure the transmitter directly onto standard 35 mm DIN-rail clips inside the industrial cabinet.
• Connect one non-contacting 3300 NSv proximity probe and its matching extension cable to the designated input terminals.
• Verify that the 2-wire loop power supply provides between plus 12 and plus 35 Vdc with total loop resistance under 1,000 ohms.
• Adjust the non-interacting external zero and span potentiometers carefully during initial system calibration.

Maintenance & Operational Usability

• The modular DIN-rail setup allows rapid physical replacement without complicated mounting procedures.
• External zero and span controls permit field calibration without requiring proprietary configuration software.
• Built-in Not OK signal defeat circuitry automatically flags probe failures or open circuits to protect the control loop.

Compatibility & System Integration

• Fully compatible with Bently Nevada 3300 NSv proximity probes and associated extension cables.
• Interfaces smoothly with standard distributed control systems or programmable logic controllers accepting 4-20 mA current loops.

Certifications & Compliance

• CSA Division 2 hazardous area approval for safe deployment in volatile industrial sectors.
• Complies with rigorous industrial manufacturing standards and carries a comprehensive 12-month service warranty.

Package Contents & Logistics

• Includes the Bently Nevada 991-25-70-01-01 transmitter unit, 35 mm DIN-rail clips, and technical documentation.
• Shipped securely via FedEx, UPS, or DHL with rapid 24-48 hour dispatch schedules.
• Backed by a full 12-month operational warranty.

Typical Applications & Diagnostic Capabilities

• Monitors axial thrust displacement on centrifugal air compressors, industrial pumps, large motors, and fans.
• Provides early warning diagnostics for thrust bearing wear, preventing catastrophic machinery failures in oil, gas, and power generation plants.

Selection Comparison & Technical Guidance

When evaluating alternative configurations, consider the 991-25-70-03-00 model if your installation layout requires different mounting clips or hardware options. Engineering teams should match the system length option (such as the 7.0-meter cable option on the 991-25-70-01-01) precisely with physical probe placement to prevent signal attenuation.

Frequently Asked Questions

Q: What causes the transmitter output to drop below 3.6 mA?
A: The Not OK/Signal Defeat circuit triggers this drop within 100 microseconds if it detects a severed probe cable, power loss, or internal sensor fault.

Q: Can I adjust the zero and span settings in the field?
A: Yes, the device features non-interacting external adjustments that allow calibration technicians to tune the 4-20 mA output directly on the DIN rail.

Q: What is the maximum allowable cable resistance for the 4-20 mA loop?
A: The maximum loop resistance is 1,000 ohms, which includes the total wiring resistance when operating at 35 Vdc.

Tags