Product Overview

The Epro PR6424/103-030 16 mm Eddy Current Sensor is a non-contact displacement measurement device designed for monitoring the operating condition of critical rotating machinery. Belonging to the PR6424 sensor family from Emerson EPRO, it is used in machinery protection and condition-monitoring systems where accurate shaft movement measurements are essential for equipment reliability.

Unlike contact-based measurement devices, an eddy current sensor measures the distance between its probe tip and a conductive metallic target without physically touching the rotating surface. This makes it suitable for continuous monitoring of rotating shafts in turbines, compressors, pumps, generators, and other industrial machines.

The PR6424 series is designed to measure several important mechanical parameters, including radial shaft vibration, axial displacement, shaft position, eccentricity, and rotational speed-related signals. These measurements help operators and maintenance engineers identify abnormal machine behavior before it develops into serious mechanical damage.

The sensor has a nominal probe-tip diameter of 16 mm. Its measurement performance is based on electromagnetic induction, with a typical sensitivity of 4 V/mm and a static measurement range of ±2.0 mm. For dynamic vibration measurement, the series supports a range of 0 to 1,000 μm.

The PR6424/103-030 is intended to operate as part of a compatible measurement system rather than as an independent monitoring instrument. A complete installation generally includes the sensor probe, the appropriate extension cable arrangement, and a compatible signal converter or monitoring channel.

Selecting the correct probe configuration is important because different PR6424 ordering codes may have different cable lengths, connector arrangements, mounting details, and compatibility requirements. The complete model number should therefore be checked before purchasing or replacing the sensor.

Technical Specifications

Note: The measurement values above are PR6424 family reference specifications. Confirm the exact mechanical, electrical, cable, connector, and temperature configuration for PR6424/103-030 before installation.

Function and Working Principle

The PR6424/103-030 operates using the eddy current measurement principle. This technology allows the sensor to detect the distance between its probe tip and a conductive target without requiring direct physical contact.

1. Electromagnetic Field Generation

An electrical signal is applied to the sensor’s internal coil, producing an electromagnetic field around the probe tip.

When the probe is positioned near a conductive metallic target, such as a rotating steel shaft, the electromagnetic field interacts with the target surface.

This interaction produces small circulating electrical currents within the conductive material. These currents are known as eddy currents.

2. Distance Measurement

The strength of the eddy currents changes according to the distance between the sensor tip and the metallic target.

When the shaft moves closer to the probe, the electromagnetic interaction changes. When the shaft moves farther away, the interaction changes in the opposite direction.

The sensor detects these variations and provides a measurement signal related to the distance between the probe and the target.

This allows the system to monitor both relatively slow shaft-position changes and faster dynamic movements associated with vibration.

3. Static Displacement Measurement

Static displacement measurement is used to monitor the relative position of a rotating shaft.

For example, axial shaft movement may occur because of changes in operating conditions, bearing conditions, thermal expansion, or mechanical loading.

The PR6424 series provides a static measurement range of ±2.0 mm, allowing the monitoring system to detect position changes within its specified operating range.

4. Dynamic Vibration Measurement

Dynamic measurement focuses on the rapid movement of a shaft during operation.

Rotating machinery may experience vibration caused by imbalance, misalignment, bearing wear, mechanical looseness, or other operating conditions.

The PR6424 series supports dynamic measurement from 0 to 1,000 μm. When installed at suitable measurement locations, the sensor can provide continuous shaft vibration information for machinery condition monitoring.

5. Signal Conversion and Processing

The sensor probe is normally connected to a compatible EPRO signal converter through the specified cable arrangement.

The converter conditions the sensor signal and produces an output suitable for a machinery monitoring system.

The resulting measurement can be displayed, recorded, or evaluated by monitoring equipment. Alarm and shutdown decisions are handled by the configured machinery protection system rather than by the probe alone.

Role in Industrial Machinery Protection Systems

The PR6424/103-030 is designed to support continuous condition monitoring in industrial equipment where shaft movement provides important information about machine health.

Shaft Vibration Monitoring

Shaft vibration is one of the most important parameters in rotating machinery diagnostics.

A sensor installed near a rotating shaft can measure changes in the distance between the probe and the shaft surface. The monitoring system uses this information to evaluate shaft vibration.

Abnormal vibration trends may indicate developing mechanical problems, including rotor imbalance, misalignment, bearing deterioration, or structural looseness.

Axial Position Monitoring

Axial displacement measurement is used to monitor movement along the shaft’s rotational axis.

This is particularly important in turbines and compressors, where excessive axial movement may affect clearances, thrust bearings, and internal mechanical components.

A properly installed eddy current sensor provides position information that can be evaluated by the machinery protection system.

Shaft Eccentricity Measurement

Shaft eccentricity refers to variations in the shaft’s position relative to its rotational center.

Monitoring eccentricity can help engineers identify mechanical irregularities and changes in shaft behavior. It is particularly useful during startup, shutdown, and changing operating conditions.

Machinery Speed and Keyphasor-Related Monitoring

Eddy current probes can also be used in suitable arrangements to detect rotational features on a shaft or target wheel.

The resulting signal can support rotational speed and phase-related measurements when the sensor, target geometry, and monitoring equipment are configured appropriately.

Predictive Maintenance

Continuous monitoring allows maintenance teams to evaluate equipment behavior over time rather than relying exclusively on periodic inspections.

By reviewing vibration and displacement trends, engineers can identify changes in machine performance and schedule maintenance based on equipment condition.

Industrial Applications

The Epro PR6424/103-030 is suitable for applications involving continuous monitoring of large rotating machinery. Its non-contact measurement method makes it useful in equipment where shaft movement must be measured without introducing mechanical contact.

1. Steam Turbines

Steam turbines operate under high mechanical and thermal loads. Shaft vibration, axial movement, and rotor eccentricity are important parameters for monitoring their operating condition.

The PR6424 series can be installed at suitable measurement points to monitor shaft movement and provide data to a machinery protection system.

Typical monitoring objectives include:

• Radial shaft vibration measurement.
• Axial displacement monitoring.
• Rotor position evaluation.
• Shaft eccentricity monitoring.
• Detection of abnormal vibration trends.

2. Gas Turbines

Gas turbines are used in power generation and industrial energy systems. Their rotating assemblies operate at high speeds and require reliable machinery protection.

Non-contact eddy current sensors can provide continuous information about shaft movement, helping operators evaluate rotor behavior during startup, normal operation, and shutdown.

3. Hydro Turbines and Generators

Hydroelectric generating equipment contains large rotating assemblies that require long-term condition monitoring.

The PR6424 series can support shaft vibration and displacement measurement in suitable hydro turbine and generator installations.

Monitoring shaft movement can help maintenance teams identify changes associated with mechanical wear, rotor imbalance, or bearing-related problems.

4. Industrial Compressors

Centrifugal and other large industrial compressors operate under demanding mechanical conditions.

Shaft vibration and position measurements provide useful information for evaluating rotor stability and mechanical condition.

The sensor can be used in a compatible compressor monitoring arrangement to provide continuous measurement data.

5. Industrial Pumps

Large pumps used in water treatment, petrochemical processing, and power generation may require continuous shaft condition monitoring.

An eddy current sensor can measure shaft displacement and vibration without contacting the rotating surface.

This is useful in applications where pump availability and operating stability are important.

6. Industrial Fans and Blowers

Large industrial fans and blowers may experience vibration due to imbalance, bearing wear, mechanical looseness, or operating changes.

A suitable eddy current monitoring arrangement can help identify abnormal shaft movement and support maintenance planning.

Installation and System Integration

Correct installation is essential for achieving reliable measurement performance. The probe position, target material, mounting arrangement, cable routing, and converter compatibility all influence measurement quality.

1. Select the Correct Mounting Location

The sensor should be installed at a measurement location that provides a suitable view of the rotating shaft surface.

The mounting position must account for shaft diameter, available clearance, target geometry, and the intended measurement direction.

The PR6424 series is designed for large rotating shafts, with a reference shaft diameter of at least 80 mm in its published application specifications.

2. Maintain the Correct Air Gap

The distance between the probe tip and the shaft surface is important for accurate measurement.

The PR6424 series has an approximate nominal center air gap of 2.7 mm. The final installation gap should be established using the applicable sensor and converter instructions.

An incorrect gap can reduce measurement accuracy or cause the system to operate outside its linear measuring range.

3. Check the Target Material

Eddy current measurement depends on the electrical and magnetic characteristics of the target material.

The PR6424 series specifies ferromagnetic steel as its reference target material, with 42CrMo4 commonly used as the standard reference material.

If the shaft uses a different material or surface treatment, engineers should verify the applicable calibration requirements.

4. Secure the Sensor Mechanically

The sensor should be mounted securely to prevent unwanted movement during machine operation.

Mechanical looseness can introduce measurement errors and may affect the reliability of vibration monitoring.

Ensure that the probe mounting arrangement follows the specified thread and mechanical configuration for the exact sensor variant.

5. Connect the Correct Cable and Converter

The PR6424 sensor must be connected to a compatible signal converter through the appropriate cable arrangement.

Before installation, verify:

• Complete sensor ordering code.
• Extension cable type and length.
• Connector configuration.
• Converter compatibility.
• Cable shielding and grounding requirements.
• Monitoring channel configuration.

Do not assume that every PR6424 sensor variant uses an identical cable or converter arrangement.

6. Route Cables Carefully

Sensor cables carry relatively low-level measurement signals and should be routed to minimize electrical interference.

Avoid unnecessary proximity to high-voltage power conductors, motor cables, and switching equipment.

Maintain the specified cable bending radius and protect the cable from excessive heat, mechanical abrasion, and vibration.

7. Perform Initial Calibration and Testing

After installation, establish the correct probe gap and verify the measurement output.

Check the signal for stability, confirm the expected measurement direction, and compare the reading with the monitoring system’s configured values.

The commissioning process should also include verification of alarms, signal scaling, and any machine protection functions associated with the measurement channel.

Compatible System Components

The PR6424/103-030 is generally used as part of a complete machinery monitoring arrangement. Its operation depends on compatible signal-conditioning and monitoring equipment.

The components listed above represent a typical measurement arrangement. They are not necessarily included with the PR6424/103-030 sensor.

Alternative Models and Replacement Considerations

The PR6424 belongs to a broader family of EPRO eddy current sensors. Other models may share the same general measurement principle but can differ in probe diameter, cable arrangement, mounting dimensions, measurement range, and application temperature.

A related model should not be treated as a direct replacement based only on its series name or probe diameter.

Before selecting an alternative, compare the complete model number, probe geometry, cable length, connector, thread, target material, converter compatibility, and operating temperature.

For critical machinery protection applications, replacement selection should also account for the existing monitoring system’s calibration and protection settings.

Key Advantages

Non-Contact Measurement

The sensor measures shaft displacement without physical contact with the rotating surface. This avoids mechanical wear at the sensing point and supports continuous monitoring.

High Measurement Sensitivity

The PR6424 series provides a typical sensitivity of 4 V/mm, allowing small changes in the distance between the probe and shaft to be detected.

Static and Dynamic Measurement

The sensor family supports both static displacement and dynamic vibration measurements, making it useful for different machinery monitoring requirements.

Compact 16 mm Probe Design

The 16 mm probe head supports installation in appropriately designed machinery monitoring locations while providing measurement capability for large rotating shafts.

Continuous Condition Monitoring

When connected to compatible signal-conditioning and monitoring equipment, the sensor can provide ongoing measurement information for machinery condition assessment.

Industrial Machinery Applications

The PR6424 series is designed for critical rotating equipment, including turbines, compressors, pumps, fans, and generators.

Integration with Machinery Protection Systems

The sensor can form part of a wider machinery monitoring arrangement that evaluates shaft movement, vibration, and position.

Technical FAQs

1. What is the Epro PR6424/103-030?

The Epro PR6424/103-030 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement and vibration in rotating machinery.

2. What is the sensor head diameter?

The nominal sensor head diameter is 16 mm, which is the standard probe diameter for the PR6424 sensor family.

3. What measurement principle does the PR6424 use?

It uses the eddy current principle. An electromagnetic field interacts with a conductive metallic target, and changes in the interaction are used to determine the distance between the probe and the target surface.

4. What is the sensitivity of the PR6424 series?

The typical sensitivity is 4 V/mm, equivalent to approximately 101.6 mV/mil. The specified linearity is up to ±1.5% for the series.

5. What is the static measurement range?

The PR6424 series has a static measurement range of ±2.0 mm. This range is used for monitoring shaft position and displacement.

6. Can the sensor measure shaft vibration?

Yes. It supports dynamic displacement measurement from 0 to 1,000 μm. When correctly installed and connected to compatible monitoring equipment, it can provide shaft vibration measurement data.

7. Which materials can be measured?

The published PR6424 reference specifications use ferromagnetic steel as the target material, with 42CrMo4 as a standard reference. Other materials may require separate verification and calibration.

8. Does the sensor work independently?

No. The sensor is normally part of a complete measurement system that includes suitable cable connections and a compatible signal converter or monitoring channel.

9. Where is the PR6424/103-030 commonly used?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, industrial pumps, fans, and generators.

10. What should be checked before replacing an existing PR6424 sensor?

Verify the complete model number, probe dimensions, mounting thread, cable length, connector type, converter compatibility, target material, and measurement configuration. A sensor with the same 16 mm diameter may still have a different cable or electrical arrangement.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/103-030, confirm the complete ordering code printed on the product label. This is particularly important for replacement projects because different PR6424 variants can have similar physical appearances but different connection and mounting configurations.

For procurement, check the following details:

• Exact model number: PR6424/103-030.
• Sensor head diameter: 16 mm.
• Cable length and construction.
• Connector type and termination arrangement.
• Mounting thread and mechanical dimensions.
• Compatibility with the installed signal converter.
• Product condition and available inspection information.
• Actual supplied weight and packaging configuration.

For maintenance, periodically inspect the sensor cable, connector, mounting hardware, and probe tip. Look for cable damage, loose connections, contamination, and mechanical movement around the mounting point.

If the measurement signal becomes unstable, check the probe gap, target surface condition, cable integrity, connector contacts, converter compatibility, and grounding arrangement.

It is also advisable to maintain records of the installed sensor model, measurement gap, converter configuration, and monitoring channel settings. These records can make future troubleshooting and replacement work more efficient.

Because the PR6424 is used in machinery monitoring applications, replacement decisions should be based on technical compatibility rather than physical appearance alone.

Conclusion

The Epro PR6424/103-030 16 mm Eddy Current Sensor is designed for non-contact monitoring of shaft displacement and vibration in critical industrial rotating machinery. Its 16 mm probe design, 4 V/mm sensitivity, ±2.0 mm static measurement range, and 0–1,000 μm dynamic measurement range make the PR6424 family suitable for a range of machinery condition-monitoring applications.

The sensor can support shaft vibration, axial displacement, position, eccentricity, and speed-related monitoring when installed as part of a compatible measurement system.

For industrial maintenance and replacement projects, verifying the complete ordering code, cable arrangement, connector configuration, and signal converter compatibility is essential to achieving reliable measurement performance.