The Bently Nevada 991-25-50-01-01 is a two-wire, loop-powered thrust transmitter designed to measure the relative axial position of a rotating machine shaft. It accepts input directly from a 3300 NSv proximity probe and extension cable, transforming the proximity signal into a proportional 4 to 20 mA current output. This device integrates directly with Programmable Logic Controllers (PLCs), Distributed Control Systems (DCSs), and SCADA networks to provide continuous machinery protection and condition monitoring. Typical industrial applications include centrifugal air compressors, small pumps, motors, and fans with fluid-film thrust bearings where a full machinery protection system monitor rack is not required.
| Option Code | Description |
|---|---|
| 991 | Thrust Transmitter |
| 25 | Full-scale Option: 25-0-25 mils |
| 50 | System Length Option: 5.0 meters (16.4 feet) |
| 01 | Mounting Option: 35 mm DIN-rail clips |
| 01 | Agency Approval Option: CSA Division 2 |
| Category | Parameter | Specification |
|---|---|---|
| Manufacturer | Brand | Bently Nevada |
| Origin | Country of Origin | United States |
| Physical | Approximate Weight | 0.43 kg |
| Dimensions (H x W x D) | 53.3 mm x 73.9 mm x 100.1 mm (2.10 in x 2.91 in x 3.94 in) | |
| Body Height (without DIN clip) | 42.6 mm (1.68 in) | |
| Mounting Hole Distance (Width x Length) | 63.5 mm x 69.9 mm (2.50 in x 2.75 in) | |
| Mounting Hole Diameter | 5.8 mm (0.23 in) | |
| Electrical | Input Voltage Range | 12 to 35 Vdc (at the transmitter terminal block) |
| Current Output | 4 to 20 mA (Linear over 50 mils range) | |
| Loop Accuracy | Within ±1.5% over specified full-scale range | |
| Maximum Loop Resistance | 1000 ohms including cable at 35 Vdc | |
| Current Limiting | 23 mA typical | |
| Dynamic | Frequency Response | DC to 10 Hz |
| BNC Connector Output | Raw proximity probe voltage buffered (Nominal 200 mV/mil) | |
| Minimum Target Size | 9.5 mm diameter | |
| Environmental | Operating Temperature | -35 to +85 Celsius |
| Storage Temperature | -51 to +100 Celsius | |
| Relative Humidity | 100% condensing, non-submerged |
| Terminal / Connector | Function |
|---|---|
| PROX | Proximity Probe Input Terminal Connection |
| COM | Signal Common / System Ground |
| +4-20mA | Positive Loop Power / Current Output Terminal |
| -4-20mA | Negative Loop Power / Current Output Terminal |
| BNC | Dynamic Signal Output (Buffered Proximity Voltage) |
The module accommodates both panel (bulkhead) and DIN rail mounting options. When using the panel mount configuration, prepare four mounting holes with a spacing layout of 63.5 mm (width) by 69.9 mm (length). Use the standard 5.8 mm diameter mounting holes or the supplied 6-32 x 1.326 screws for secure bulkhead fixation. For DIN rail configurations, ensure a standard 35 mm DIN rail is rigidly installed before snapping on the transmitter's DIN mount clips.
Proper grounding is essential to minimize noise interference. The transmitter must be mounted to a grounded plate or a grounded DIN rail. Ensure the cable shield is grounded at only one end, typically at the control room/DCS side, to prevent ground loops.
Before final commissioning, the proximity probe must be physically positioned (gapped) relative to the shaft target. Adjust the gap until the transmitter output reads approximately 12 mA, which corresponds to the midpoint of the linear thrust range (0 mils).
Run probe and loop cables in dedicated, grounded metal conduits or cable trays. Avoid routing transmitter cables parallel to high-voltage AC power lines or heavy machinery switching circuits to prevent electro-magnetic interference (EMI).
When installed in classified areas, appropriate intrinsic safety barriers or explosion-proof housings must be utilized in accordance with local electrical codes and the specific installation drawings provided by the manufacturer.
What is the primary function of this thrust transmitter?
It measures the axial displacement or thrust position of a rotating machine shaft relative to a fixed reference point using a non-contacting proximity probe.
What type of probe system is compatible with this transmitter?
It is designed specifically to interface with a Bently Nevada 3300 NSv proximity probe and extension cable system.
How is the device powered?
It is a loop-powered device operating on a 12 to 35 Vdc supply connected via the 4 to 20 mA current loop.
What does the BNC connector provide?
The BNC connector provides a buffered raw voltage signal proportional to the probe gap distance, allowing engineers to connect diagnostic equipment like oscilloscopes or analyzers without disconnecting the loop.
Can this device be used for radial vibration measurements?
No, this specific model is configured and calibrated for thrust (axial) position measurement. For radial vibration, a 990 Vibration Transmitter should be used.
What is the function of the Not OK/Signal Defeat circuit?
The circuit forces the signal output to drop below 3.6 mA within 100 microseconds of a probe fault or loose connection to prevent false alarms in the control system.
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Manufacturer: Bently Nevada
Product No.: 991-25-50-01-01
Country of origin:United States
Product Type: Thrust Transmitter
Barcode: 8537101190
Payment: T/T, Western Union
Weight: 430g
Dimensions: 53.3 mm x 73.9 mm x 100.1 mm
Shipping port: Xiamen
Warranty: 12 months
The Bently Nevada 991-25-50-01-01 is a two-wire, loop-powered thrust transmitter designed to measure the relative axial position of a rotating machine shaft. It accepts input directly from a 3300 NSv proximity probe and extension cable, transforming the proximity signal into a proportional 4 to 20 mA current output. This device integrates directly with Programmable Logic Controllers (PLCs), Distributed Control Systems (DCSs), and SCADA networks to provide continuous machinery protection and condition monitoring. Typical industrial applications include centrifugal air compressors, small pumps, motors, and fans with fluid-film thrust bearings where a full machinery protection system monitor rack is not required.
| Option Code | Description |
|---|---|
| 991 | Thrust Transmitter |
| 25 | Full-scale Option: 25-0-25 mils |
| 50 | System Length Option: 5.0 meters (16.4 feet) |
| 01 | Mounting Option: 35 mm DIN-rail clips |
| 01 | Agency Approval Option: CSA Division 2 |
| Category | Parameter | Specification |
|---|---|---|
| Manufacturer | Brand | Bently Nevada |
| Origin | Country of Origin | United States |
| Physical | Approximate Weight | 0.43 kg |
| Dimensions (H x W x D) | 53.3 mm x 73.9 mm x 100.1 mm (2.10 in x 2.91 in x 3.94 in) | |
| Body Height (without DIN clip) | 42.6 mm (1.68 in) | |
| Mounting Hole Distance (Width x Length) | 63.5 mm x 69.9 mm (2.50 in x 2.75 in) | |
| Mounting Hole Diameter | 5.8 mm (0.23 in) | |
| Electrical | Input Voltage Range | 12 to 35 Vdc (at the transmitter terminal block) |
| Current Output | 4 to 20 mA (Linear over 50 mils range) | |
| Loop Accuracy | Within ±1.5% over specified full-scale range | |
| Maximum Loop Resistance | 1000 ohms including cable at 35 Vdc | |
| Current Limiting | 23 mA typical | |
| Dynamic | Frequency Response | DC to 10 Hz |
| BNC Connector Output | Raw proximity probe voltage buffered (Nominal 200 mV/mil) | |
| Minimum Target Size | 9.5 mm diameter | |
| Environmental | Operating Temperature | -35 to +85 Celsius |
| Storage Temperature | -51 to +100 Celsius | |
| Relative Humidity | 100% condensing, non-submerged |
| Terminal / Connector | Function |
|---|---|
| PROX | Proximity Probe Input Terminal Connection |
| COM | Signal Common / System Ground |
| +4-20mA | Positive Loop Power / Current Output Terminal |
| -4-20mA | Negative Loop Power / Current Output Terminal |
| BNC | Dynamic Signal Output (Buffered Proximity Voltage) |
The module accommodates both panel (bulkhead) and DIN rail mounting options. When using the panel mount configuration, prepare four mounting holes with a spacing layout of 63.5 mm (width) by 69.9 mm (length). Use the standard 5.8 mm diameter mounting holes or the supplied 6-32 x 1.326 screws for secure bulkhead fixation. For DIN rail configurations, ensure a standard 35 mm DIN rail is rigidly installed before snapping on the transmitter's DIN mount clips.
Proper grounding is essential to minimize noise interference. The transmitter must be mounted to a grounded plate or a grounded DIN rail. Ensure the cable shield is grounded at only one end, typically at the control room/DCS side, to prevent ground loops.
Before final commissioning, the proximity probe must be physically positioned (gapped) relative to the shaft target. Adjust the gap until the transmitter output reads approximately 12 mA, which corresponds to the midpoint of the linear thrust range (0 mils).
Run probe and loop cables in dedicated, grounded metal conduits or cable trays. Avoid routing transmitter cables parallel to high-voltage AC power lines or heavy machinery switching circuits to prevent electro-magnetic interference (EMI).
When installed in classified areas, appropriate intrinsic safety barriers or explosion-proof housings must be utilized in accordance with local electrical codes and the specific installation drawings provided by the manufacturer.
What is the primary function of this thrust transmitter?
It measures the axial displacement or thrust position of a rotating machine shaft relative to a fixed reference point using a non-contacting proximity probe.
What type of probe system is compatible with this transmitter?
It is designed specifically to interface with a Bently Nevada 3300 NSv proximity probe and extension cable system.
How is the device powered?
It is a loop-powered device operating on a 12 to 35 Vdc supply connected via the 4 to 20 mA current loop.
What does the BNC connector provide?
The BNC connector provides a buffered raw voltage signal proportional to the probe gap distance, allowing engineers to connect diagnostic equipment like oscilloscopes or analyzers without disconnecting the loop.
Can this device be used for radial vibration measurements?
No, this specific model is configured and calibrated for thrust (axial) position measurement. For radial vibration, a 990 Vibration Transmitter should be used.
What is the function of the Not OK/Signal Defeat circuit?
The circuit forces the signal output to drop below 3.6 mA within 100 microseconds of a probe fault or loose connection to prevent false alarms in the control system.
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Returns & Warranty
Orders are processed and delivered Monday-Friday (excluding public holidays).
For full eligibility, restocking fees, and international return details, please view our official Refund & Return Policy .
| Color pattern |
Greyish White
Black
|
| Country of origin |
United States
|
| Power source |
DC Power
|
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