21504-00-28-05-02 | Bently Nevada 8 mm Proximity Probe Vibration Transducer

Introduction to the 21504-00-28-05-02 Proximity Probe

For maintenance engineers, reliable vibration monitoring is essential to prevent unplanned downtime. The 21504-00-28-05-02 from Bently Nevada delivers accurate proximity measurements in harsh industrial environments. This 8 mm probe is part of the 7200 Proximity Transducer System, designed for continuous operation in rotating machinery applications. With a calibrated range of 80 mils (2.0 mm) and a scale factor of 200 mV/mil (7.87 V/mm), it provides consistent data for predictive maintenance programs.

Key Features and Technical Specifications

• Diameter: 8 mm probe tip for standard mounting configurations.
• Calibrated Range: 80 mils (2.0 mm), beginning at approximately 10 mils (0.25 mm) from the probe face.
• Scale Factor: 200 mV/mil (7.87 V/mm), ±4% when calibrated as a system.
• Linearity: Within 0.8 mils (0.02 mm) of a 200 mV/mil straight line as a system; within 2.3 mils (0.06 mm) including interchangeability errors.
• Frequency Response: 0 to 10 kHz (0 to 600,000 cpm); -5% at 10 kHz (600,000 cpm).
• Power Input: -17.5 Vdc to -26 Vdc at 12 mA maximum consumption.
• Temperature Sensitivity: Typically -396 change in scale factor at +150°F (+65°C) at 50 mils gap (1.27 mm).
• Operating Temperature (Probe): -30°F to +350°F (-34°C to +177°C).
• System Weight: 1.3 lbs (0.59 kg).

One distinctive specification is the frequency response up to 10 kHz, which enables detection of high-speed machinery faults such as gear mesh or blade pass vibrations. This makes the 21504-00-28-05-02 suitable for turbines, compressors, and pumps operating at elevated speeds.

Real-World Applications

In petrochemical plants, the 21504-00-28-05-02 monitors shaft vibration in centrifugal compressors. Similarly, power generation facilities use it for turbine bearing vibration analysis. Its corrosion resistance to air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, and DMF allows direct contact with common industrial fluids. Consequently, it performs reliably in wet or chemically aggressive environments without performance degradation.

Installation and Setup Guidance

When installing the 21504-00-28-05-02, ensure the probe face is positioned correctly relative to the target surface. The calibrated range begins at approximately 10 mils (0.25 mm) from the probe face, so initial gap setting is critical. Use the provided 3/8-24 threads for secure mounting. The unthreaded length option is 0 mm, and the overall case length is 2.8 inches. For optimal signal integrity, route the coaxial connector (option 02) away from high-voltage cables. Always verify the power supply meets the -17.5 Vdc to -26 Vdc requirement at 12 mA maximum.

Maintenance and Reliability Tips

Routine inspection of the probe tip and cable is recommended to ensure no physical damage or contamination. The probe operates reliably in relative humidity up to 95% noncondensing. Because the 21504-00-28-05-02 is designed for continuous duty, periodic verification of the scale factor and linearity using a calibration fixture helps maintain measurement accuracy. For long-term reliability, follow Bently Nevada's recommended maintenance intervals as outlined in the product manual.

Compatibility and Integration

The 21504-00-28-05-02 integrates with Bently Nevada 7200 series monitoring systems and other compatible vibration monitoring platforms. It uses a miniature male coaxial connector for signal output. When replacing older probes, verify the system's input requirements match the -17.5 Vdc to -26 Vdc power specification. For new installations, consult the system manual to confirm compatibility with existing cabling and junction boxes.

Frequently Asked Questions

Q: What is the calibrated range of the 21504-00-28-05-02?

A: The calibrated range is 80 mils (2.0 mm), beginning at approximately 10 mils (0.25 mm) from the probe face.

Q: What power supply is required for this probe?

A: It requires -17.5 Vdc to -26 Vdc at 12 mA maximum consumption.

Q: What is the frequency response of the 21504-00-28-05-02?

A: The frequency response is 0 to 10 kHz (0 to 600,000 cpm), with -5% at 10 kHz.

Q: Is the probe resistant to chemicals?

A: Yes, for 8 mm probes, operation is not affected by direct contact with air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, or DMF.

Q: What is the operating temperature range for the probe?

A: The probe and extension cable operate from -30°F to +350°F (-34°C to +177°C).

Product Support and Availability

The 21504-00-28-05-02 is available as a new and original factory-packed unit from Petro Auto Tech. It comes with a 12-month factory warranty. For lifecycle status and ordering assistance, contact Petro Auto Tech directly.