Product Overview

The Epro PR6424/106-101 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the condition and operating behavior of rotating machinery. Part of the PR6424 sensor family from Emerson EPRO, it is used in machinery protection and condition-monitoring systems where accurate measurement of shaft movement is important.

The sensor operates using the eddy-current measurement principle. Instead of touching the rotating shaft, it detects changes in the electromagnetic field caused by the distance between the sensor tip and a conductive target. These changes are converted into an electrical signal that can be processed by a compatible signal converter and monitoring system.

In industrial machinery, shaft displacement and vibration measurements can provide important information about equipment condition. Changes in shaft position, vibration amplitude, or rotational behavior may indicate mechanical problems such as bearing wear, rotor imbalance, misalignment, or changes in operating conditions. Continuous monitoring helps maintenance teams identify abnormal behavior and investigate potential problems before they develop into more serious failures.

The PR6424 series features a 16 mm sensor head and is intended for applications involving relatively large rotating shafts. Typical monitored equipment includes steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans.

The PR6424/106-101 is identified as a specific ordering variant within this sensor family. Its exact cable arrangement, connector configuration, mounting details, and temperature specification should be checked against the complete product identification before installation or replacement.

Technical Specifications

Note: The measurement figures above are PR6424 family reference specifications. Confirm the exact PR6424/106-101 cable, connector, mounting, and temperature configuration before installation. The supplied weight is retained as the product listing value.

Function and Working Principle

The PR6424/106-101 uses electromagnetic induction to measure the distance between the sensor tip and a conductive metallic target. This technology enables continuous shaft displacement measurement without direct mechanical contact.

1. Eddy Current Measurement

The sensor contains an electrical coil that generates a high-frequency electromagnetic field near its sensing tip. When a conductive target, such as a steel shaft, enters this field, electrical currents known as eddy currents are induced in the target surface.

These currents influence the electromagnetic characteristics of the sensor coil. As the distance between the sensor and the target changes, the electrical response also changes.

The sensor system uses this relationship to determine the relative distance between the probe tip and the shaft surface. Because measurement takes place without physical contact, the sensor can monitor rotating equipment without introducing mechanical friction at the measurement point.

2. Shaft Displacement Measurement

Shaft displacement measurement provides information about the position of a rotating shaft relative to the sensor mounting location.

The PR6424 sensor can be used to monitor static shaft position within its measurement range. This information is relevant during equipment startup, shutdown, load changes, and normal operation.

Changes in shaft position may help maintenance engineers investigate bearing clearance, thermal expansion, mechanical movement, or other changes in the rotating assembly.

3. Shaft Vibration Monitoring

When the shaft moves dynamically, the distance between the shaft surface and the sensor changes continuously. The resulting signal can represent shaft vibration.

The PR6424 family has a reference dynamic measurement range of 0–1,000 μm. When connected to a compatible signal converter and monitoring system, the measurement can be used to evaluate vibration amplitude and operating trends.

This information is particularly useful for large rotating machinery, where excessive shaft vibration can affect bearing performance, mechanical stability, and equipment availability.

4. Signal Conversion

The sensor probe is normally part of a complete measurement chain. Its electrical response is processed by a compatible signal converter, which produces an output suitable for machinery monitoring equipment.

The complete measurement chain generally includes:

• Eddy current sensor probe.
• Compatible extension cable, where required.
• Matching signal converter.
• Machinery protection or monitoring system.
• Monitoring software or operator interface.

The probe, cable, and converter must be electrically compatible. Incorrect combinations can affect measurement sensitivity, calibration, and signal accuracy.

5. Continuous Condition Monitoring

When installed in a machinery protection system, the sensor can provide continuous measurement information during equipment operation.

Monitoring systems can use this information to identify changes in shaft displacement or vibration. Engineers can then compare current measurements with established operating baselines and alarm limits.

The sensor itself does not independently diagnose every mechanical fault. Reliable condition assessment requires correct installation, appropriate signal processing, and interpretation of the measurements in the context of the machine.

Role in Industrial Machinery Protection Systems

The PR6424/106-101 is designed to operate as a sensing component within a broader machinery monitoring architecture.

Turbine Monitoring

Steam, gas, and hydro turbines contain rotating assemblies that operate under demanding mechanical and thermal conditions. Monitoring shaft displacement and vibration helps engineers evaluate rotor behavior and identify abnormal operating trends.

A suitable sensor installation can provide measurement signals to a turbine protection system for continuous monitoring.

Compressor Protection

Industrial compressors are commonly used in chemical processing, oil and gas facilities, refrigeration systems, and manufacturing plants.

Shaft vibration measurements can help maintenance teams evaluate rotor stability and investigate changes that may be associated with bearing problems, imbalance, or mechanical misalignment.

Pump Monitoring

Large industrial pumps may operate continuously under changing pressure and flow conditions. Monitoring shaft movement can provide useful information about mechanical condition.

The PR6424 sensor can be considered for suitable pump installations where non-contact shaft displacement measurement is required.

Integration with Monitoring Equipment

The sensor must be paired with an appropriate signal converter and monitoring hardware. The monitoring system receives the processed signal and can display measurement values, trends, and alarm conditions.

Before replacing an existing probe, engineers should verify the sensor model, cable configuration, converter compatibility, measurement range, and calibration requirements.

Industrial Applications

1. Steam Turbines

Steam turbines are used in power generation and industrial energy systems. Their rotating shafts operate at high speeds and require reliable mechanical monitoring.

The PR6424 sensor family can be used for non-contact shaft displacement and vibration measurement in suitable turbine monitoring arrangements. Continuous measurement helps operators observe rotor behavior during startup, normal operation, and shutdown.

2. Gas Turbines

Gas turbines are used in power plants, industrial facilities, and mechanical drive applications. Stable rotor operation is important for equipment reliability.

Eddy current sensing can provide information about shaft movement without requiring physical contact with the rotating component.

3. Hydro Turbines

Hydro turbines operate in power generation environments where shaft alignment, bearing condition, and mechanical stability are important.

Suitable displacement sensors can support monitoring of shaft position and dynamic movement, helping maintenance teams evaluate changes in operating behavior.

4. Industrial Compressors

Centrifugal and other large compressors often operate continuously in critical process applications.

Shaft vibration monitoring can provide information about rotor condition and help identify unusual vibration trends. The sensor must be installed at a suitable measurement location and paired with a compatible monitoring system.

5. Industrial Pumps

Large pumps used in water treatment, chemical processing, and industrial circulation systems may require continuous machinery monitoring.

The PR6424 series can support non-contact shaft measurement where the machine design and sensor installation requirements are suitable.

6. Industrial Fans

Large fans and blowers are widely used in ventilation, combustion-air supply, and process exhaust systems.

Monitoring shaft vibration can help maintenance teams identify changes in mechanical behavior and plan inspection activities.

Installation and System Integration

Correct sensor installation is essential for measurement accuracy and long-term reliability.

1. Confirm the Sensor Configuration

Before installation, check the complete model number printed on the sensor identification label. The PR6424 family contains different ordering variants, and these may differ in cable length, connector arrangement, mounting configuration, and other details.

Do not assume that every PR6424 probe is interchangeable simply because it has the same 16 mm sensor head diameter.

2. Check the Mounting Location

The sensor should be installed at a position that provides a suitable measurement surface and sufficient mechanical clearance.

The mounting arrangement must maintain the required distance from the shaft and avoid interference from nearby metallic objects. The sensor should be secured against movement during operation.

Follow the applicable installation drawing for probe orientation, mounting thread, and mechanical clearances.

3. Establish the Correct Air Gap

The nominal center air gap for the PR6424 family is approximately 2.7 mm. The actual installation gap should be established according to the manufacturer’s calibration and installation instructions.

An incorrect air gap can reduce measurement accuracy or cause the signal to operate outside its intended linear range.

The final adjustment should be checked using the compatible signal converter and the required calibration procedure.

4. Verify Target Material

Eddy current sensor performance depends on the electrical and magnetic properties of the target material.

The PR6424 family specifications use ferromagnetic steel as the reference target material. Shaft material and surface condition should therefore be considered during installation and calibration.

A different target material may affect sensitivity and measurement characteristics.

5. Route and Protect the Cable

The sensor cable should be routed away from high-power conductors, strong electromagnetic interference sources, and locations where it may be exposed to mechanical damage.

Observe the cable’s minimum bending radius and temperature limitations. Avoid excessive pulling, twisting, or sharp bends.

Where the installation environment is demanding, suitable cable protection and secure routing should be provided.

6. Connect the Compatible Signal Converter

The sensor must be paired with a compatible converter and extension cable arrangement. Verify the complete measurement-chain configuration before connecting the equipment.

Using a converter designed for a different sensor type or electrical configuration may produce incorrect readings or prevent normal operation.

7. Perform Calibration and Functional Testing

After installation, confirm that the probe signal changes correctly as the target distance changes. Verify the nominal air gap, signal output, measurement polarity, and calibration settings.

The monitoring system should be checked for normal measurement values and appropriate alarm behavior before the machinery is returned to service.

Compatible System Components

The PR6424/106-101 is normally used as part of a complete machinery monitoring system. The following components describe the typical roles within that measurement chain.

The components listed above are examples of a typical monitoring arrangement. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 is part of a wider EPRO eddy current sensor family. Other sensor models may appear similar but can have different measurement ranges, sensing diameters, operating temperatures, and installation requirements.

Before selecting an alternative, compare:

• Sensor head diameter.
• Measurement sensitivity and linearity.
• Static and dynamic measurement ranges.
• Nominal air gap.
• Target material and shaft diameter.
• Sensor operating temperature.
• Cable length and connector type.
• Extension cable compatibility.
• Signal converter compatibility.
• Mounting thread and mechanical dimensions.

A sensor with a similar measurement principle is not necessarily a direct replacement. The complete probe and converter combination must be evaluated together.

Key Advantages

Non-Contact Measurement

The eddy current principle allows the sensor to measure shaft movement without touching the rotating surface. This avoids mechanical contact between the probe and shaft during normal operation.

Suitable for Rotating Machinery

The PR6424 family is designed for monitoring large rotating equipment, including turbines, compressors, pumps, and fans.

Displacement and Vibration Measurement

The sensor can provide information about both static shaft position and dynamic shaft movement when used with compatible measurement equipment.

Compact 16 mm Sensor Head

The 16 mm sensor head provides a defined sensing geometry for suitable machinery installations.

Industrial Monitoring Integration

The sensor can be incorporated into a compatible machinery protection and condition-monitoring system.

Continuous Measurement Capability

When installed as part of a suitable monitoring arrangement, the probe supports continuous observation of shaft movement and vibration trends.

Established EPRO Sensor Technology

The PR6424 family is used in industrial machinery monitoring applications where non-contact displacement measurement is required.

Technical FAQs

1. What is the Epro PR6424/106-101?

The Epro PR6424/106-101 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement and vibration in suitable rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm, as specified for the PR6424 family.

3. What is the measurement principle?

It uses electromagnetic induction. The sensor generates an electromagnetic field, and changes in the distance to a conductive target affect the electrical response of the sensor.

4. What is the typical sensitivity of the PR6424 series?

The published PR6424 family reference sensitivity is 4 V/mm, with linearity of approximately ±1.5% maximum. Confirm the applicable documentation for the exact probe configuration.

5. What is the static measurement range?

The PR6424 family has a reference static measurement range of ±2.0 mm.

6. Can this sensor measure shaft vibration?

Yes. When used with a compatible signal converter and monitoring system, the sensor can measure dynamic shaft movement and provide information used for vibration monitoring.

7. What type of shaft material is suitable?

The PR6424 family specifications use ferromagnetic steel as the reference target material. The actual shaft material should be checked against the applicable sensor documentation.

8. What is the nominal center air gap?

The typical PR6424 family nominal center air gap is approximately 2.7 mm. Final installation adjustment must follow the manufacturer’s instructions and calibration procedure.

9. Does the sensor connect directly to a PLC?

The sensor is normally connected to a compatible signal converter or machinery monitoring system. The processed measurement signal may then be integrated into a PLC or control system if the installed monitoring equipment supports the required interface.

10. What should be checked before replacing a PR6424/106-101?

Verify the full model number, sensor head diameter, cable arrangement, connector, mounting configuration, temperature requirements, converter compatibility, and calibration settings. A similar-looking probe may not have the same electrical or mechanical characteristics.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/106-101, verify the complete model number and inspect the product identification label. Confirm that the supplied sensor matches the required cable and connector arrangement in the existing machinery monitoring system.

For replacement projects, compare the old and new sensor configurations before installation. Pay particular attention to probe length, cable length, connector type, mounting thread, and converter compatibility. These details can affect the complete measurement chain even when two probes have the same 16 mm sensor head diameter.

For used or surplus sensors, request clear photographs of the probe body, identification label, cable, and connector. Check for damaged insulation, bent connectors, corrosion, and visible mechanical damage. Where possible, request functional test information and confirmation of the sensor’s condition.

During maintenance, inspect the mounting arrangement and cable routing. Ensure that the probe remains securely positioned and that the cable is protected from excessive heat, vibration, and mechanical stress.

If measurement values become unstable, investigate the entire measurement chain rather than replacing the probe immediately. Possible causes include an incorrect air gap, damaged cable, unsuitable target surface, poor connections, incompatible converter, or incorrect calibration.

Conclusion

The Epro PR6424/106-101 16 mm Eddy Current Sensor is an industrial non-contact displacement sensor intended for monitoring the movement and vibration of rotating machinery. Its PR6424 family reference specifications include a 16 mm sensor head, 4 V/mm sensitivity, ±2.0 mm static measurement range, and a dynamic measurement range of 0–1,000 μm.

The sensor can be used in suitable turbine, compressor, pump, and fan monitoring applications when connected to a compatible signal converter and machinery protection system. For maintenance and replacement projects, verifying the complete ordering code, cable arrangement, mounting configuration, and measurement-chain compatibility is essential for reliable operation.