The Bently Nevada 991-25-70-01-CN, also cataloged as the 991-25-70-01-CN 991 Thrust Transmitter, operates as a dedicated hardware component for axial shaft position measurement within machinery protection monitoring systems. The transmitter processes 3300 NSv proximity probe signals and converts thrust displacement into a 4-20 mA loop-powered output.
Hardware Specifications
Parameter
Specification
Model
991-25-70-01-CN
Brand
Bently Nevada
Product Type
Thrust Transmitter
Series
991
Origin
USA
Input Type
3300 NSv non-contacting proximity probe with extension cable
Measurement Function
Axial shaft displacement / thrust position monitoring
Measurement Range
25-0-25 mils
Linear Range
0.25 to 1.65 mm
Output Signal
4-20 mA DC
Output Configuration
2-wire loop-powered transmitter
Power Supply
+12 to +35 VDC
System Length
7.0 m (23.0 ft)
Mounting Type
35 mm DIN-rail mounting clips
Loop Accuracy
Typically within +/-1.5 % of full scale
Maximum Loop Resistance
1000 ohms at 35 VDC including cable
Current Limitation
Approximately 23 mA
Signal Failure Output
Less than 3.6 mA within 100 us
Zero and Span Adjustment
External non-interactive adjustment
Operating Temp
-35 deg C to +85 deg C
Storage Temp
-51 deg C to +100 deg C
Probe Operating Temp
-35 deg C to +177 deg C
Probe Storage Temp
-51 deg C to +177 deg C
Weight
Approximately 0.43 kg
Dimensions
53.3 mm x 73.9 mm x 100.1 mm
Power Consumption
Loop-powered operation, dependent on supply voltage and loop resistance
Eddy-Current Probe Scaling and Rotor Dynamics Processing
The 991-25-70-01-CN uses an eddy-current measurement interface to process displacement signals from the 3300 NSv proximity probe. The transmitter applies probe scaling characteristics to convert gap-related voltage changes into proportional shaft position data.
The system design includes gap voltage validation principles based on eddy-current probe operation. A typical probe operating point uses a -10 VDC gap voltage target to maintain measurement linearity and displacement accuracy.
The transmitter output represents axial rotor movement and supports rotor dynamics analysis by providing continuous thrust position feedback. Signal conditioning functions maintain measurement stability by reducing electrical interference effects during machinery operation.
Frequently Asked Questions
Q: What type of input sensor is compatible with the 991-25-70-01-CN? A: The transmitter accepts input from a Bently Nevada 3300 NSv non-contacting proximity probe with a matching extension cable system.
Q: What electrical output does the transmitter provide? A: The unit provides a proportional 4-20 mA DC signal through a 2-wire loop-powered configuration.
Q: Does the transmitter require cabinet mounting hardware? A: The device uses 35 mm DIN-rail clips for installation inside industrial control panels.
Field Installation Guidelines
Install the transmitter on a standard 35 mm DIN rail inside a protected control cabinet environment.
Connect the proximity probe, extension cable, and transmitter input wiring according to the approved Bently Nevada installation documentation.
Maintain proper cable routing separation between probe wiring and high-voltage power conductors to reduce electrical interference.
Verify probe gap voltage before commissioning to confirm correct eddy-current measurement operation.
Connect the 4-20 mA loop with correct polarity and confirm loop power availability before operation.
Use shielded instrumentation wiring where required and terminate cable shields according to site grounding practices.
Perform zero and span adjustment verification after mechanical installation and shaft position alignment.
