Thrust Transmitter | 991-01-XX-02-05 | 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). 

Features

Not OK / Signal Failure Protection Circuit: In the event of a broken or loose probe cable or probe damage, the transmitter will immediately reduce the loop current to below 3.6 mA within 100 microseconds (µs). This allows the control system to instantly identify a "sensor hardware failure," preventing false trips.

Power-up Inhibit Circuit: Automatically suppresses erroneous data spikes in the first few seconds during system startup power-up voltage transients, ensuring signal stability.

Suitable for Confined Spaces: Specifically designed for compact bearing housing environments where traditional eddy current probes cannot be installed due to insufficient side clearance, when used with the 3300 NSv Narrow Side View probe.

Convenient Calibration and Testing

Includes independent zero and full-scale potentiometers below the transmitter label for easy on-site loop calibration and adjustment.

Features a test input pin, allowing for quick verification of the loop output current by introducing a variable DC voltage source without probe removal.

Technical FAQ

Q: What major global safety and explosion-proof certifications are included in the "05" suffix of 991-01-XX-02-05?

A: "05" indicates Multiple Approvals certification. The transmitter complies with CSA Division 2 (North America), ATEX Zone 0, and ATEX Zone 2 (Europe) hazardous-area safety requirements.

Q: What static displacement measurement range is specified by the leading "01" option in 991-01-XX-02-05?

A: In the standard electrical calibration of the 991 transmitter, the "01" option represents an axial displacement range with a total travel of 50 mils (approximately 1.27 mm), electrically mapped to a symmetrical 25-0-25 mils thrust position range.

Q: How does a control system interpret the 4-20 mA output signal from 991-01-XX-02-05 in a two-wire loop?

A: The module linearly maps displacement to a 4-20 mA current signal. A loop current of 12 mA corresponds precisely to the physical center position (0 mils). Current values below 12 mA indicate axial movement toward the probe, while values above 12 mA indicate movement away from the probe.

Q: How can the Test Input terminal on 991-01-XX-02-05 be used for loop integrity testing?

A: Without disconnecting the probe, maintenance personnel can apply a variable DC voltage signal to the Test Input terminal to simulate displacement changes. This allows verification of the 4-20 mA loop performance and PLC/DCS interlock logic while the machine remains in operation.

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.

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