21504-08-20-10-02 | Bently Nevada 8 mm Probe Proximity Vibration Transducer

Introduction to the Bently Nevada 21504-08-20-10-02

When machinery vibration threatens uptime, the 21504-08-20-10-02 from Bently Nevada provides critical measurement accuracy. This 8 mm probe proximity vibration transducer is part of the 7200 Proximity Transducer Systems family, engineered for continuous monitoring of rotating equipment. With a calibrated range of 80 mils (2.0 mm) and a scale factor of 200 mV/mil (7.87 V/mm), it delivers reliable data for predictive maintenance programs.

Key Features & Technical Specifications

The 21504-08-20-10-02 offers several performance attributes that support precise vibration measurement:

• 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 if calibrated as a system.
• Frequency response: 0 to 10 kHz (0 to 600,000 cpm); -5% at 10 kHz.
• Power input: -17.5 Vdc to -26 Vdc at 12 mA maximum consumption.
• Operating temperature (probe and 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 distinctive spec is the temperature sensitivity: typically -3% change in scale factor at +150°F (+65°C) at 50 mils gap (1.27 mm). This characteristic helps users anticipate measurement drift in high-temperature environments.

Applications & Use Cases

Industrial facilities rely on the 21504-08-20-10-02 for vibration monitoring on pumps, compressors, turbines, and fans. Its 8 mm probe diameter suits tight mounting spaces, while the 1.0 metre (39 inches) total length with a miniature male coaxial connector simplifies integration. The probe resists direct contact with air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, or DMF, making it suitable for harsh environments. For example, in a refinery, this transducer can monitor critical rotating assets where exposure to chemicals and high temperatures is common.

Installation & Setup

Mount the 8 mm probe using the 3/8-24 thread configuration. Ensure the unthreaded length of 80 mm and overall case length of 2.0 inches match your mounting requirements. The total length tolerance is +0.25 metre, -0.10 metre (+10 inches, -4 inches). Connect the miniature male coaxial connector to the Proximitor for signal processing. Verify the gap voltage at installation to confirm the probe is within the calibrated range.

Maintenance & Reliability

Regular inspection of the probe tip and cable helps maintain measurement integrity. The system operates reliably in temperatures from -30°F to +350°F (-34°C to +177°C) for the probe and extension cable. Periodic verification of the scale factor and linearity per the manufacturer's guidelines ensures continued accuracy. Because the transducer is designed for continuous duty, routine checks reduce unplanned downtime and extend service life.

Compatibility & Integration

The 21504-08-20-10-02 integrates with Bently Nevada Proximitors and monitoring systems from the 7200 series. It outputs a proportional DC voltage that can be fed into vibration monitors, data collectors, or distributed control systems. For system calibration, pair the probe with a compatible Proximitor to achieve the specified ±4% scale factor accuracy.

Comparison with Similar Products

Compared to other 8 mm proximity probes, the 21504-08-20-10-02 offers a calibrated range of 80 mils (2.0 mm) and a scale factor of 200 mV/mil. Some competing probes may provide a shorter range or different scale factor. The frequency response of 0 to 10 kHz covers most rotating machinery vibration frequencies. The temperature sensitivity of typically -3% at +150°F is a known characteristic that users should account for in high-temperature applications.

FAQs about the 21504-08-20-10-02

What is the calibrated range of the 21504-08-20-10-02?

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

What is the scale factor of this Bently Nevada probe?

The scale factor is 200 mV/mil (7.87 V/mm), ±4% when calibrated as a system.

What power supply does the 21504-08-20-10-02 require?

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

What is the operating temperature range for the probe?

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

What is the frequency response of this transducer?

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

Product Support & Availability

The Bently Nevada 21504-08-20-10-02 is available as new and original in factory packing from Petro Auto Tech. It ships with a 12-month factory warranty. For current lifecycle status and ordering details, contact Petro Auto Tech directly.