Description
Conditioning dynamic eddy current signals for high-reliability machinery diagnostics, the Bently Nevada 330878-90-CN operates as a key component of the 3300 XL 50 mm Proximitor Sensor system. This unit converts the radio frequency (RF) signal generated by the proximity probe into a proportional voltage output, enabling precise measurements of shaft displacement, vibration, and position in heavy rotating machinery. The specific -90-CN configuration designates a 9.0-meter system length with panel-mounting capability and regional-specific safety certifications.
Features
- Optimized for the high-aperture fields of 50 mm proximity probes.
- 9.0-meter (29.5 feet) total system length calibration matches probe and extension cable impedance.
- Rugged panel-mount design for secure installation within industrial junction boxes or instrument enclosures.
- Corrosion-resistant A380 cast aluminum housing provides superior durability in harsh environments.
- CN agency approval designation for country-specific regulatory compliance.
Applications
- Thrust and radial vibration monitoring on large utility-scale steam and gas turbines.
- Shaft centerline tracking and displacement analysis in hydroelectric generators.
- Mechanical protection loops for high-horsepower industrial compressors and process pumps.
- Torsional and structural displacement monitoring in power generation and marine propulsion.
Technical Specifications Table
| Parameter |
Specification Value |
| Manufacturer |
Bently Nevada (Baker Hughes) |
| Model Number |
330878-90-CN |
| Sensor Series |
3300 XL 50 mm |
| System Length |
9.0 meters (29.5 feet) |
| Mounting Configuration |
Panel Mount |
| Housing Material |
A380 Aluminum |
| Operating Temperature |
-51 degC to +100 degC (-60 degF to +212 degF) |
| Storage Temperature |
-51 degC to +105 degC (-60 degF to +221 degF) |
| Agency Approvals |
CN (Country Specific Approvals) |
| Shipping Weight (Calculated) |
3.0 kg (6.6 lbs) |
| Country of Origin |
United States |
Connections and Interfaces
| Terminal / Port |
Function / Circuit Assignment |
| Coaxial Jack |
Accepts RF cable connection from the 3300 XL 50 mm extension cable / probe assembly. |
| Terminal VT |
Power input supply (-24 Vdc nominal). |
| Terminal OUT |
Dynamic output voltage signal (proportional to target distance). |
| Terminal COM |
Common ground reference. |
Alternative Models & Compatibility
The 330878-90-CN must only be paired with 3300 XL 50 mm proximity probes and equivalent 9.0-meter matching systems. It is not interchangeable with 8 mm or 11 mm Proximitor sensors, as the internal oscillators and linearization curves are explicitly tuned for the electromagnetic footprint of the large 50 mm probe head. Intermixing components across different millimeter-scale families will lead to severe calibration drift and false machine trip signals.
Application Pitfalls & Engineering Notes
The 50 mm sensor system generates a broad electromagnetic field. Ensure that a clear, unobstructed side-clearance zone is maintained around the probe head to prevent parasitic targets (such as machine casing walls or internal brackets) from entering the detection field. Operating outside the rated temperature envelope (-51 degC to +100 degC) will degrade the sensor's temperature compensation circuitry, introducing measurement offset errors.
Commissioning & Wiring Tips
Always check the coaxial connector insulation prior to startup. The outer connector sleeve must be kept completely isolated from the machine ground; utilize Bently Nevada connector protectors or silicone heat-shrink tubing over the coaxial junctions. For signal integrity, route field wiring inside dedicated, grounded conduit, keeping it physically separated from high-voltage motor supply runs to minimize electromagnetic interference.
Installation Guidelines
CRITICAL WARNING
Isolate and lock out all external power sources before handling terminal block wiring. Failure to de-energize active monitoring systems prior to connection can introduce electrical transients that may cause damage to the monitoring rack input cards or trigger spurious turbine emergency trips.
1
Mount the Proximitor housing securely on the subpanel using the integrated mounting flanges. Ensure the mounting plate has a solid path to the structural instrument ground.
2
Connect the 9.0-meter extension cable coaxial plug to the sensor's coaxial jack. Hand-tighten the connector and ensure the mechanical locking mechanism is secure.
3
Install three-wire shielded instrument cabling to the VT, OUT, and COM screw terminals, maintaining proper torque to prevent loose terminations.
4
Ground the cable shield exclusively at the monitor rack/safety barrier end; do not connect the shield to ground at the Proximitor sensor terminal block to avoid ground loops.