Manufacturer: Bently Nevada
Product No.: 991-25-50-02-05
Country of origin:United States
Product Type: 991 Thrust Transmitter
Barcode: 8537101190
Payment: T/T, Western Union
Weight: 430g
Dimensions: 81.3 mm x 61.2 mm x 103.4 mm
Shipping port: Xiamen
Warranty: 12 months
The 991 Thrust Transmitter converts axial shaft displacement signals into a proportional 4 to 20 mA output for machinery control and protection systems. The unit is designed for centrifugal air compressors, pumps, motors, and fans requiring continuous thrust position monitoring through a simple loop-powered interface.
The Bently Nevada 991-25-50-02-05 is a 2-wire loop-powered transmitter compatible with the 3300 NSv proximity probe system using a 5 m extension cable configuration. The transmitter conditions the probe signal into engineering units proportional to shaft axial position and transmits the signal directly to PLC, DCS, or machinery protection systems.
The transmitter integrates the Proximitor sensor internally and does not require an external signal conditioning module. Diagnostic access is available through non-isolated PROX OUT and COM terminals together with a coaxial connector for vibration and gap voltage monitoring.
The unit supports bulkhead mounting and includes non-interacting zero and span adjustments for loop calibration. A dedicated test input pin allows verification of loop output using a variable DC voltage source.
The potted housing design supports installation in high-humidity industrial environments. The transmitter is commonly used in OEM rotating machinery packages where compact thrust monitoring is required.
| Code | Description |
|---|---|
| 991 | Thrust Transmitter |
| 25 | +/-25 mils full-scale range |
| 50 | 5.0 m system length |
| 02 | Bulkhead mounting screws |
| 05 | Agency approval option |
| Category | Specification |
|---|---|
| Manufacturer | Bently Nevada |
| Product Type | Thrust Transmitter |
| Model | 991-25-50-02-05 |
| Series | 991 |
| Country of Origin | USA |
| Input Type | 3300 NSv proximity probe and extension cable |
| System Length | 5.0 m |
| Signal Output | 4 to 20 mAdc |
| Power Supply | 12 to 35 Vdc |
| Loop Accuracy | +/-1.5% full scale |
| Maximum Loop Resistance | 1000 Ohm at 35 Vdc |
| Frequency Response | DC to 10 kHz |
| Current Limiting | 23 mA typical |
| Response Time | <100 us fault response |
| Operating Temperature | -35 degC to +85 degC |
| Storage Temperature | -51 degC to +100 degC |
| Relative Humidity | 100% condensing, non-submerged |
| Transmitter Weight | 0.43 kg |
| Total System Weight | 0.82 kg typical |
| Dimensions | 100 x 74 x 53.3 mm |
| Mounting Method | Bulkhead mounting screws |
| Probe Cable Type | 75 Ohm coaxial FEP insulated |
| Transducer Case Material | AISI 303 or 304 stainless steel |
| Transducer Tip Material | Polyphenylene sulfide (PPS) |
| Connector Pin | Function |
|---|---|
| E1-E2 | Power supply and 4-20 mA output |
| E3-E4 | Proximitor connection |
| J2 | PROX OUT diagnostic connection |
| J3 | Probe connection |
| PROX OUT | Dynamic vibration signal output |
| COM | Common diagnostic terminal |
Install the transmitter in a dry control enclosure or protected machinery panel area. Maintain proper shielding and grounding practices for all probe and signal cables to reduce EMI and RFI interference.
Route proximity probe cables separately from high-voltage power wiring. Avoid excessive bending or mechanical stress on coaxial cables during installation.
Verify probe gap adjustment according to the machinery shaft position requirements before commissioning. Incorrect probe positioning may prevent full-scale measurement operation.
Use isolated diagnostic equipment when accessing the PROX OUT signal. The diagnostic output is non-isolated from the 4 to 20 mA loop.
Provide sufficient ventilation around the transmitter when installed in enclosed cabinets with elevated ambient temperatures.
| Standard | Description |
|---|---|
| FCC Part 15 | EMC compliance |
| EN 61000-6-2 | EMC immunity |
| EN 61000-6-4 | EMC emissions |
| EMC Directive 2014/30/EU | European EMC compliance |
| ATEX Directive 2014/34/EU | Hazardous area approval |
| RoHS Directive 2011/65/EU | RoHS compliance |
| ABS 2009 Steel Vessels Rules | Maritime approval |
| CSA/NRTL/C Class I Div 2 | Hazardous location approval |
| ATEX/IECEx Ex ia IIC T4 Ga | Intrinsically safe approval |
What does the 991 transmitter measure?
It measures axial shaft displacement and converts the signal into a proportional 4 to 20 mA output.
Which probe system is compatible with this transmitter?
The unit is designed for use with the 3300 NSv proximity probe system.
Is the transmitter loop powered?
Yes. It operates as a 2-wire loop-powered device.
Can the transmitter provide vibration diagnostics?
Yes. The PROX OUT connection provides dynamic vibration and gap voltage signals.
What mounting method does this version use?
This model uses bulkhead mounting screws.
Does the transmitter require an external Proximitor module?
No. The Proximitor sensor is integrated into the transmitter.
What is the output signal type?
The standard output is 4 to 20 mAdc.
Can the transmitter connect directly to a PLC or DCS?
Yes. The output is suitable for standard industrial control system analog inputs.
What is the supported operating temperature range?
The operating range is -35 degC to +85 degC.
Is the housing suitable for humid environments?
Yes. The potted construction supports high-humidity environments.
What happens during a probe fault condition?
The NOT OK circuit drives the output below 3.6 mA during a fault condition.
Can the loop output be tested without machinery movement?
Yes. A test input pin supports loop verification using a variable DC source.
Does the transmitter support hazardous area installations?
Yes. The unit includes CSA and ATEX/IECEx approvals depending on configuration.
What industries commonly use this transmitter?
It is widely used in compressor, pump, motor, and rotating equipment monitoring systems.
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| Color pattern |
Greyish White
Black
|
| Country of origin |
United States
|
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