Product Overview

The Epro PR6424/012-021 16 mm Eddy Current Sensor is a non-contact displacement measurement device designed for monitoring the condition and operating behavior of rotating industrial machinery. It belongs to the EPRO PR6424 sensor family, which is associated with Emerson’s machinery health monitoring portfolio.

Eddy current sensors are widely used in critical rotating equipment because they can measure shaft movement without requiring physical contact with the rotating surface. This makes them suitable for continuous monitoring of vibration, displacement, shaft position, eccentricity and other mechanical conditions.

The PR6424/012-021 has a sensor head diameter of 16 mm and a supplied product weight of approximately 0.2 kg. Its measurement principle is based on changes in an electromagnetic field when a conductive target, such as a steel shaft, moves relative to the probe tip.

In a typical installation, the sensor is positioned near the rotating shaft with a carefully adjusted initial air gap. The resulting measurement signal is processed by a compatible signal converter or monitoring system. This allows the equipment monitoring system to evaluate shaft movement and identify changes that may indicate mechanical wear, imbalance, misalignment or other abnormal operating conditions.

The PR6424 family is intended for critical turbomachinery applications, including steam turbines, gas turbines, hydro turbines, compressors, pumps and fans. Its non-contact measurement capability makes it useful in installations where continuous shaft-condition information is important for equipment protection and maintenance planning.

Technical Specifications

Note: The performance figures above are general PR6424 series specifications. Exact temperature limits, cable length, connector type, probe construction and converter compatibility must be confirmed for the complete PR6424/012-021 part number.

Function and Working Principle

The PR6424/012-021 uses eddy current technology to measure the distance between the sensor tip and a conductive target. It does not need to touch the rotating shaft, making it suitable for continuous monitoring of machinery operating at high speed.

1. Electromagnetic Field Generation

The sensor contains a coil that generates a high-frequency electromagnetic field at its sensing tip. When a conductive metal target approaches the probe, the field induces small circulating electrical currents known as eddy currents in the target surface.

The induced currents influence the electrical characteristics of the sensor coil. Changes in the distance between the probe and the target therefore produce corresponding changes in the sensor’s electrical response.

2. Displacement Measurement

As the shaft moves toward or away from the sensor, the distance between the target surface and probe tip changes.

The sensor detects these changes and produces a measurement response that can be processed by a compatible signal converter. Within its specified linear measurement range, the output can be used to determine shaft displacement.

This measurement principle supports both static and dynamic monitoring. Static measurements can be used to assess shaft position, while dynamic measurements help identify vibration and other rapid mechanical movements.

3. Vibration Monitoring

Shaft vibration is an important indicator of rotating equipment condition. Excessive vibration may be associated with imbalance, shaft misalignment, bearing deterioration, mechanical looseness or other equipment problems.

By continuously measuring shaft movement, the PR6424 sensor provides information that can be used by machinery protection and condition monitoring systems.

4. Signal Conversion

The sensor is normally used with a compatible signal converter and monitoring electronics. The converter processes the probe’s electrical response and provides a usable measurement signal for monitoring equipment.

The converter must match the probe’s electrical characteristics and exact configuration. The sensor should not be connected directly to an unrelated PLC analog input without an appropriate signal-conditioning arrangement.

Role in Industrial Machinery Monitoring Systems

The PR6424/012-021 can serve as a measurement component in a machinery protection or condition monitoring installation. It provides shaft-related measurement information that helps operators and maintenance engineers assess the condition of rotating equipment.

Turbine Shaft Monitoring

Steam, gas and hydro turbines contain rotating shafts that operate under demanding mechanical and thermal conditions. Monitoring shaft vibration and displacement can help identify changes in mechanical behavior.

Eddy current probes are commonly installed at selected measurement locations to monitor radial or axial shaft movement.

Compressor Condition Monitoring

Industrial compressors are often critical to continuous production. Unexpected mechanical problems can lead to reduced performance, equipment damage and unplanned downtime.

A shaft displacement sensor can provide measurement information for detecting changes in vibration and shaft position. This information can be incorporated into a broader machinery monitoring strategy.

Pump Monitoring

Large industrial pumps may operate continuously in power generation, chemical processing, water treatment and other process industries.

The PR6424 series can be used in suitable pump installations to monitor shaft movement and support condition-based maintenance.

Integration with Protection Systems

The sensor is part of a measurement chain rather than a complete protection system by itself. A typical installation includes:

• PR6424 eddy current probe.
• Compatible extension cable, where required.
• Matching signal converter.
• Machinery monitoring or protection equipment.
• Alarm and shutdown interfaces.
• Plant control or supervisory system.

The complete measurement chain must be correctly matched and calibrated to provide meaningful monitoring data.

Industrial Applications

1. Steam Turbines

Steam turbines operate at high rotational speeds and are important assets in power generation and industrial energy systems.

The PR6424 sensor family can be used to monitor shaft vibration and displacement in suitable turbine installations. Continuous measurement helps operators observe changes in shaft behavior and evaluate whether operating conditions remain within established limits.

2. Gas Turbines

Gas turbines are used in power plants, industrial facilities and mechanical drive applications. Their rotating assemblies require reliable condition monitoring because mechanical problems can affect equipment availability and operating safety.

Non-contact shaft measurement provides information that can support vibration analysis and machinery protection.

3. Hydro Turbines

Hydro turbines operate under different mechanical and environmental conditions from steam and gas turbines. Shaft movement monitoring can help identify changes in alignment, vibration and mechanical condition.

The PR6424 family is designed for applications involving large rotating shafts, subject to the specific installation requirements.

4. Industrial Compressors

Compressors are widely used in petrochemical plants, refineries, gas processing facilities and manufacturing operations.

Shaft displacement measurements can help maintenance teams identify changes in rotating equipment behavior and support preventive maintenance programs.

5. Large Industrial Pumps

Large pumps are used in cooling systems, water treatment facilities, power plants and industrial process installations.

The sensor can provide non-contact shaft measurement in compatible pump-monitoring arrangements, helping operators evaluate equipment condition during continuous operation.

6. Industrial Fans

Large fans and blower systems are used in ventilation, combustion air supply and process gas handling.

Where the shaft arrangement and measurement requirements are appropriate, eddy current sensors can contribute to continuous vibration and displacement monitoring.

Installation and System Integration

Correct installation is essential for accurate measurement. The sensor must be positioned and configured according to the shaft material, measurement direction, mounting arrangement and compatible converter specifications.

1. Confirm the Sensor Configuration

Before installation, verify the complete model number PR6424/012-021. Confirm the cable arrangement, connector, probe dimensions, thread specification and compatible signal converter.

Different PR6424 variants may have different cable lengths, mechanical configurations or converter compatibility. A similar-looking sensor should not automatically be treated as interchangeable.

2. Select the Measurement Location

The probe should be mounted at a location that provides a stable measurement surface and suitable access for installation and maintenance.

For shaft vibration measurement, engineers generally select measurement locations based on the machine’s bearing arrangement and monitoring requirements.

The target material and shaft geometry must comply with the sensor’s specifications.

3. Set the Initial Air Gap

The initial distance between the sensor tip and shaft surface is important for measurement accuracy.

The PR6424 series specification gives an approximate nominal center air gap of 2.7 mm. The actual installation gap must be established using the correct calibration procedure and compatible converter.

An incorrect gap can reduce measurement accuracy or place the sensor outside its linear operating range.

4. Secure the Probe

Install the sensor using the specified mounting arrangement. Ensure that the probe is mechanically stable and protected against unintended movement.

The cable should be routed so that it is not exposed to excessive tension, sharp bends, vibration damage or high temperatures beyond its specified limits.

5. Connect the Signal Converter

Connect the sensor to a compatible signal converter using the correct cable and connector arrangement.

Check the converter model, electrical compatibility and calibration requirements before applying power. The converter should be configured for the specific probe characteristics.

6. Verify the Measurement Signal

After installation, confirm that the output changes appropriately when the shaft position or calibration gap changes.

Check the signal for abnormal fluctuations, excessive noise or unstable readings. Verify the measurement against the commissioning requirements before connecting it to the machinery protection or monitoring system.

Compatible System Components

The PR6424/012-021 is normally used as part of a complete machinery measurement system.

A complete measurement installation may require additional cables, converters, mounting accessories and monitoring modules. These components are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 belongs to a wider family of EPRO eddy current sensors. Other models may have similar measurement principles but can differ in mechanical dimensions, cable arrangement, temperature capability and electrical configuration.

When replacing a PR6424/012-021, check the following:

• Complete model and suffix.
• Sensor head diameter.
• Probe length and mounting thread.
• Cable length and connector type.
• Sensor operating temperature.
• Sensitivity and linearity.
• Static and dynamic measurement range.
• Compatible signal converter.
• Target material and shaft dimensions.
• Calibration and installation requirements.

A replacement should not be selected based on sensor diameter alone. Electrical and mechanical compatibility are both essential for reliable measurement.

Key Advantages

Non-Contact Measurement

The sensor measures shaft movement without physical contact. This avoids direct mechanical wear at the sensing interface and supports continuous monitoring.

16 mm Sensor Head

The 16 mm probe design is intended for large rotating machinery applications where the measurement arrangement requires this sensor size.

High Measurement Sensitivity

The PR6424 series specification lists a sensitivity of 4 V/mm, supporting the measurement of small changes in shaft position.

Static and Dynamic Measurement

The series supports static displacement measurement and dynamic vibration measurement within its specified operating ranges.

Machinery Protection Applications

The sensor can provide important shaft measurement information for machinery condition monitoring and protection systems.

Industrial Rotating Equipment Compatibility

The PR6424 family is intended for applications involving turbines, compressors, pumps and fans, subject to correct mechanical and electrical configuration.

Integration with Monitoring Systems

When paired with a compatible signal converter, the sensor can be incorporated into machinery monitoring and plant automation architectures.

Technical FAQs

1. What is the Epro PR6424/012-021?

The PR6424/012-021 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement and vibration in industrial rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm.

3. What is the measuring principle?

It uses eddy current technology. An electromagnetic field generated by the probe interacts with the conductive shaft surface, allowing the sensor system to detect changes in the distance between the probe and target.

4. What is the sensitivity of the PR6424 series?

The manufacturer’s PR6424 series specification lists a sensitivity of 4 V/mm, with linearity within ±1.5%.

5. What is the static measurement range?

The published static measurement range is ±2.0 mm.

6. What is the dynamic measurement range?

The published dynamic measurement range is 0 to 1,000 μm.

7. What machinery can use this sensor?

The PR6424 family is designed for critical rotating machinery, including steam turbines, gas turbines, hydro turbines, compressors, pumps and fans.

8. Does the sensor require a signal converter?

A compatible signal converter or monitoring interface is normally required to process the probe signal and provide a usable measurement output.

9. Can the sensor connect directly to a PLC?

It should not be assumed that the probe can connect directly to a standard PLC analog input. A compatible signal converter or monitoring interface is generally required.

10. What should be checked before replacing the sensor?

Verify the complete part number, probe diameter, cable arrangement, connector, mounting dimensions, converter compatibility and calibration requirements.

11. What is the weight of the PR6424/012-021?

The supplied product listing weight is approximately 0.2 kg. The manufacturer’s general PR6424 specification also gives approximately 200 grams for a sensor with a 1-meter cable and without armor.

12. Why is the initial air gap important?

The initial air gap establishes the operating point of the measurement system. If it is incorrect, the sensor may operate outside its intended linear range and provide inaccurate displacement readings.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/012-021, verify the complete model number and inspect the probe’s mechanical and electrical configuration. Confirm whether the sensor is supplied with an integrated cable, connector or other accessories.

For replacement projects, compare the original probe with the proposed replacement. Pay particular attention to the mounting thread, sensor head diameter, cable length, converter compatibility and calibration requirements.

During maintenance, inspect the sensor tip, cable insulation, connectors and mounting hardware. Look for signs of mechanical damage, contamination, excessive cable bending or loose connections.

If the measurement signal becomes unstable, investigate the complete measurement chain rather than replacing the probe immediately. Potential causes include an incorrect air gap, damaged cable, poor connector contact, incompatible converter settings, electrical interference or changes in the shaft target surface.

For critical machinery, keep records of sensor installation positions, calibration values, converter settings and alarm thresholds. These records help maintenance teams compare measurements over time and identify changes in equipment condition.

Conclusion

The Epro PR6424/012-021 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement and vibration in critical rotating machinery. Its 16 mm sensor head and the PR6424 family’s published measurement characteristics make it suitable for appropriately configured monitoring applications involving turbines, compressors, pumps and fans.

With a published sensitivity of 4 V/mm, a static measuring range of ±2.0 mm and a dynamic range of up to 1,000 μm, the PR6424 series provides measurement information for machinery condition monitoring and protection systems.

For reliable operation, the sensor must be matched with the correct signal converter, cable arrangement and mounting configuration. Verifying the complete PR6424/012-021 part number is essential when purchasing, installing or replacing this industrial sensor.