Thrust Transmitter | 991-01-XX-01-CN | Bently Nevada

Technical Specifications

991 Thrust Transmitter is intended primarily for the original equipment manufacturers (OEMs) of centrifugal air compressors or small pumps, motors, or fans who prefer to provide a simple 4 to 20 mA proportional axial displacement (thrust) signal as the input to their machinery control system. The transmitter is a 2-wire, loop-powered device that accepts input from our 3300 NSv proximity probe and its matching extension cable (available in 5 m and 7 m system length options). 

Core Functions

Signal Integrity Protection (Not OK/Signal Defeat): Built-in probe status monitoring circuit. If the probe is damaged or the cable is loose, the transmitter will automatically lock the output to prevent false alarms or erroneous interlocking actions.

Power-up Inhibit: Eliminates false alarms caused by transient fluctuations in line voltage, ensuring safety during equipment startup.

Field Adjustability: Zero and span potentiometers below the label provide non-interfering operation, facilitating loop calibration and fine-tuning by process engineers.

Field Wiring Notes

PROX OUT and COM (Diagnostic Outputs): Provides unscaled raw gap voltage. Field maintenance personnel can use a multimeter or Bentley's dedicated 990/991 test adapter to connect a portable data acquisition instrument for spectrum analysis or zero-point calibration.

TEST INPUT: Using an external variable DC voltage source, this pin allows for quick verification of the 4-20 mA loop output without moving the actual probe.

Technical FAQ

Q: What specific explosion-proof certifications are represented by the "CN" designation in 991-01-XX-01-CN?

A: "CN" indicates that the transmitter is certified by NEPSI (National Supervision and Inspection Center for Explosion Protection and Safety of Instrumentation), ATEX, and IECEx, meeting stringent Intrinsic Safety (Ex ia) requirements for hazardous-area applications.

Q: What axial measurement range is represented by the leading "01" option in 991-01-XX-01-CN?

A: In the standard electrical calibration of the 991 Series, the "01" option represents an axial displacement measurement range with a total travel of 50 mils (approximately 1.2 mm), typically defined as a symmetrical 25-0-25 mils thrust position range.

Q: How can a PLC or DCS read axial position through the 4-20 mA signal of 991-01-XX-01-CN?

A: The transmitter operates on a standard two-wire loop-powered circuit. Its output current is linearly mapped to axial position: 12 mA corresponds precisely to the mechanical zero position (0 mils), current values below 12 mA indicate shaft movement toward the probe, and current values above 12 mA indicate movement away from the probe.

Q: How should the "XX" code be selected when ordering 991-01-XX-01-CN based on the field hardware configuration?

A: "XX" represents the total nominal system length of the proximity probe and extension cable. If the total cable system length is 5.0 meters, select 991-01-50-01-CN. If the total system length is 7.0 meters, select 991-01-70-01-CN.

Q: Are your products brand new?
A: Yes. We only supply 100% original and brand-new products. All items are sourced through authorized channels and have never been used or refurbished.

Q: Why can customers buy with confidence?
A: Because every product is backed by our 1-Year Warranty Guarantee of Quality, ensuring reliability, customer satisfaction, and long-term support after delivery.

Q: Do you provide international shipping?
A: Yes. We ship products to customers worldwide using reliable international logistics services such as EMS, DHL, UPS, and FedEx.

Trusted by 5,000+ plants worldwide |  Contact for more Bently Nevada spares: sales1@amikon.cn

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