21508-02-12-05-02 | Bently Nevada 0.5m 8mm Proximity Probe

Overview of the Bently Nevada 21508-02-12-05-02 Proximity Probe

When machine vibration threatens uptime, the 21508-02-12-05-02 from Bently Nevada provides reliable, real-time data. This proximity probe is part of the 7200 Proximity Transducer System, engineered for continuous monitoring in demanding industrial environments. With a calibrated range of 80 mils (2.0 mm) and a scale factor of 200 mV/mil, it delivers accurate displacement readings essential for predictive maintenance.

As a maintenance engineer, you need sensors that perform consistently. This probe operates from -17.5 Vdc to -26 Vdc at 12 mA maximum consumption, ensuring stable output. Its frequency response spans 0 to 10 kHz (0 to 600,000 cpm), capturing both slow shaft movement and high-speed vibration events.

Key Features and Technical Specifications

• Part Number: 21508-02-12-05-02
• Model: Probe Proximity Vibration
• Manufacturer: Bently Nevada
• Total Length: 0.5 metre (20 inches) with tolerance +0.13 m / -0.05 m
• Power Supply: -17.5 Vdc to -26 Vdc at 12 mA maximum consumption
• Calibrated Range: 80 mils (2.0 mm), begins at approximately 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); -5% at 10 kHz
• 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: To 95%, noncondensing
• System Weight: 1.3 lbs. (0.59 kg)

One standout feature is the probe's corrosion resistance for 8 mm probes. It withstands direct contact with air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, and DMF. This makes it suitable for harsh environments where chemical exposure is a concern.

Applications and Use Cases

In rotating machinery monitoring, the 21508-02-12-05-02 excels at measuring shaft vibration and position. Typical applications include turbines, compressors, pumps, and motors where early detection of abnormal vibration prevents catastrophic failure. For example, in a petrochemical plant, this probe can monitor a high-speed compressor, providing data that helps schedule maintenance before bearing wear becomes critical.

Furthermore, its 0.5-meter cable length suits installations where the probe must be mounted close to the measurement point. The miniature male coaxial connector ensures a secure connection, reducing signal loss. Whether you are retrofitting an older system or upgrading to modern monitoring, this probe integrates seamlessly with Bently Nevada's 7200 series.

Installation and Setup

Proper installation is key to accurate readings. Begin by verifying the total length option (05) matches your required cable run. The probe tip diameter is 8 mm, and the case configuration is reverse mount with 3/8-24 threads. Ensure the mounting hole is clean and free of debris before threading the probe.

Connect the miniature male coaxial connector to the extension cable, then route the cable away from high-voltage sources to avoid interference. Power the system with -17.5 Vdc to -26 Vdc, observing polarity. After installation, perform a system calibration to achieve the ±4% scale factor accuracy. Always follow the manufacturer's manual for specific wiring and mounting torque values.

Maintenance and Reliability

Routine inspection of the probe and cable is essential for long-term reliability. Check for physical damage, such as cuts or kinks in the cable, and verify that the probe face is clean and free of buildup. The corrosion-resistant design minimizes chemical damage, but regular visual checks help catch issues early.

Environmental factors like temperature and humidity can affect performance. The proximitor operates from -60°F to +212°F, while the probe and cable handle -30°F to +350°F. In high-humidity areas, ensure the enclosure remains sealed to prevent condensation. By following a simple maintenance schedule, you extend the life of the probe and maintain measurement integrity.

Compatibility and Integration

This probe is designed for use with Bently Nevada's 7200 Proximity Transducer Systems. It works with compatible proximitors and extension cables to form a complete monitoring solution. The output signal, 200 mV/mil, interfaces directly with Bently Nevada monitors and diagnostic equipment.

For new installations, verify that your existing system supports the 8 mm probe format. The reverse mount configuration and 3/8-24 threads are standard, but always confirm compatibility with your specific monitor model. If you are unsure, consult the official Bently Nevada documentation or contact Petro Auto Tech for guidance.

Frequently Asked Questions

Q: What is the calibrated range of the 21508-02-12-05-02?

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 does the probe require?

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

Q: Can the probe withstand harsh chemicals?

A: Yes, the 8 mm probe is corrosion-resistant to air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, and DMF.

Q: What is the frequency response of this probe?

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

Q: What are the operating temperature limits?

A: The proximitor operates from -60°F to +212°F, while the probe and extension cable handle -30°F to +350°F.

Product Support and Availability

The 21508-02-12-05-02 is available from Petro Auto Tech in new, original factory packaging. It includes a 12-month factory warranty. For lifecycle status and availability, please contact Petro Auto Tech before ordering. Our team is ready to assist with your vibration monitoring needs.