21508-02-12-10-02 | Bently Nevada 8 mm Proximity Probe

Introduction: Precision Vibration Monitoring with the 21508-02-12-10-02

When rotating machinery experiences unexpected vibration, unplanned downtime can cost thousands per hour. The 21508-02-12-10-02 from Bently Nevada provides the accurate, reliable measurements needed to detect issues early. This 8 mm proximity probe is engineered for continuous operation in demanding industrial environments.

As part of the 7200 Proximity Transducer Systems, this model offers a calibrated range of 80 mils (2.0 mm), starting at approximately 10 mils (0.25 mm) from the probe face. That means you get clear, usable data from the moment the probe is installed.

Key Features and Technical Specifications

• Part Number: 21508-02-12-10-02
• Model: Probe Proximity Vibration
• Manufacturer: Bently Nevada
• Total Length: 1.0 metre (39 inches) with tolerance of +0.25 m / -0.10 m
• Connector: Miniature male coaxial connector
• Probe Diameter: 8 mm
• Threads: 3/8-24
• Power Input: -17.5 Vdc to -26 Vdc at 12 mA maximum consumption
• Calibrated Range: 80 mils (2.0 mm), begins at ~10 mils (0.25 mm) from 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 (system calibrated)
• Frequency Response: 0 to 10 kHz (0 to 600,000 cpm)
• Temperature Sensitivity: Typically -3% change in scale factor at +150°F (+65°C) at 50 mils gap
• Operating Temperature (Proximitor): -60°F to +212°F (-51°C to +100°C)
• Operating Temperature (Probe & Extension Cable): -30°F to +350°F (-34°C to +177°C)
• Relative Humidity: Up to 95%, noncondensing
• System Weight: 1.3 lbs (0.59 kg)

One standout feature is the frequency response up to 10 kHz (600,000 cpm). This allows the probe to capture high-speed vibration events that slower sensors might miss, giving you a more complete picture of machine health.

Real-World Applications

This proximity probe is ideal for monitoring shaft vibration in turbines, compressors, pumps, and motors. In a typical scenario, an engineer installs the 21508-02-12-10-02 on a critical pump. The probe continuously measures shaft displacement, and the data feeds into a vibration monitoring system. When vibration levels rise, maintenance teams receive an alert, allowing them to schedule repairs before a catastrophic failure occurs.

Because the probe is corrosion-resistant to air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, and DMF, it can be used in harsh environments without degradation. This makes it suitable for chemical plants, refineries, and offshore platforms.

Installation and Setup

Proper installation is crucial for accurate readings. The 21508-02-12-10-02 comes with a 1.0 metre cable and a miniature male coaxial connector. When mounting, ensure the probe face is positioned at the correct gap—the calibrated range starts at approximately 10 mils (0.25 mm) from the target surface. Use the 3/8-24 threads to secure the probe in place, and avoid overtightening.

For best results, follow the manufacturer's guidelines for cable routing and grounding. The system weight of 1.3 lbs (0.59 kg) makes it easy to handle during installation.

Maintenance and Reliability

Routine inspection of the probe and cable is recommended to ensure reliable operation. Check for physical damage, loose connections, or contamination on the probe face. The probe is designed to withstand direct contact with many industrial fluids, but periodic cleaning with a soft cloth may be necessary if buildup occurs.

Given the temperature limits—up to +212°F (+100°C) for the Proximitor and +350°F (+177°C) for the probe—this unit can operate in high-heat areas without issue. Regular verification of the scale factor and linearity, per the manufacturer's manual, helps maintain measurement accuracy over time.

Compatibility and Integration

The 21508-02-12-10-02 is part of the 7200 Proximity Transducer Systems, so it is designed to work with compatible Bently Nevada monitors and diagnostic equipment. The output signal is a proportional voltage (200 mV/mil), which can be fed into standard vibration monitoring systems for analysis.

For integration details, consult the official Bently Nevada documentation or contact Petro Auto Tech for assistance.

Common Questions and Troubleshooting

Q: What is the calibrated range of the 21508-02-12-10-02?

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?

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

Q: Can this probe be used in high-temperature environments?

A: Yes, the Proximitor operates from -60°F to +212°F (-51°C to +100°C), and the probe and extension cable handle -30°F to +350°F (-34°C to +177°C).

Q: What is the frequency response?

A: The frequency response is 0 to 10 kHz (0 to 600,000 cpm).

Q: Is the probe corrosion-resistant?

A: Yes, it resists air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, and DMF.

Availability and Support

The 21508-02-12-10-02 is available from Petro Auto Tech as a new, original factory-packed unit. It includes a 12-month factory warranty. Contact Petro Auto Tech for current stock and delivery options.