Product Overview

The Epro PR6424/106-000 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the condition and operating behavior of large rotating machinery. Part of the PR6424 sensor family from Emerson EPRO, it is used in machinery protection and condition-monitoring systems where accurate shaft movement measurements are important for equipment reliability.

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

The PR6424 series is designed to measure radial and axial shaft displacement, shaft position, eccentricity, and vibration-related movement. These measurements help operators and maintenance engineers identify changes in machinery behavior that may indicate bearing wear, shaft misalignment, mechanical looseness, rotor imbalance, or other developing conditions.

The PR6424 sensor uses a 16 mm sensing head and operates according to the electromagnetic eddy-current principle. When the probe is positioned near a suitable ferromagnetic target, the electromagnetic interaction changes with the distance between the probe and the target. A compatible signal converter processes this response and produces an electrical output that can be used by a machinery protection or monitoring system.

The PR6424 family has a typical sensitivity of 4 V/mm and a specified linearity of up to ±1.5%. Its static measurement range is ±2.0 mm, while its dynamic measurement range extends from 0 to 1,000 μm. These characteristics make the sensor suitable for applications requiring continuous monitoring of shaft position and vibration.

The PR6424/106-000 is identified as a specific variant within this sensor family. When selecting a replacement or integrating it into an existing installation, users should verify the complete model designation, cable configuration, connector arrangement, mounting dimensions, and compatibility with the associated signal converter.

Technical Specifications

Note: The performance figures are PR6424 family specifications. The exact cable length, connector, mounting arrangement, and environmental limits for PR6424/106-000 should be confirmed against its complete ordering information. The approximately 0.2 kg reference weight applies to the sensor with a 1 m cable without armor.

Function and Working Principle

The PR6424/106-000 uses electromagnetic induction to measure the distance between the sensor head and a conductive metallic target. This non-contact measurement method is particularly useful for rotating machinery because the probe can continuously monitor shaft movement without direct mechanical contact.

1. Eddy Current Measurement Principle

The sensor generates an alternating electromagnetic field around its sensing tip. When a conductive target, such as a suitable ferromagnetic steel shaft, enters this field, electrical currents known as eddy currents are induced in the target surface.

These currents affect the electromagnetic characteristics of the sensor coil. The resulting electrical response changes according to the distance between the probe and the target.

A compatible signal converter interprets this change and produces an output corresponding to the measured displacement.

Because the sensor does not need to touch the shaft, it can monitor movement while the machine is operating at high rotational speeds.

2. Shaft Displacement Measurement

Shaft displacement monitoring is an important part of rotating machinery protection. A change in the shaft’s position may indicate mechanical conditions that require investigation.

The PR6424 series can measure static shaft position within its specified measurement range. This information can be used to monitor changes in the shaft’s operating position relative to the sensor mounting point.

Radial displacement measurements are particularly useful for evaluating shaft movement associated with bearing conditions, rotor imbalance, and mechanical alignment.

3. Shaft Vibration Monitoring

Rotating shafts naturally experience some degree of movement during operation. However, excessive or abnormal vibration may indicate a developing mechanical problem.

The PR6424 sensor can measure dynamic shaft displacement within its specified range. Its output can be processed by compatible monitoring equipment to evaluate vibration amplitude and changes in shaft behavior.

Continuous measurement helps maintenance teams identify abnormal trends before they develop into more serious mechanical failures.

4. Sensitivity and Linear Measurement

The PR6424 series has a typical sensitivity of 4 V/mm, equivalent to approximately 101.6 mV/mil.

Sensitivity describes how much the sensor output changes in response to a given displacement. A stable and predictable relationship between distance and output voltage is important for accurate machinery monitoring.

The specified linearity of up to ±1.5% supports consistent measurement across the applicable linear operating range.

5. Non-Contact Operation

The non-contact measurement principle reduces mechanical wear because the probe does not physically contact the rotating shaft.

This is particularly important in turbines and compressors, where continuous operation, high shaft speeds, and demanding environmental conditions make contact-based measurement impractical.

The sensor can therefore provide continuous displacement information without introducing mechanical friction at the measurement point.

Role in Industrial Machinery Protection Systems

The PR6424/106-000 is a sensing component rather than a complete machinery protection system. It normally operates together with a compatible signal converter and monitoring equipment.

Its measurements can be used to evaluate the mechanical condition of critical rotating assets.

Machinery Protection

In a machinery protection arrangement, the sensor monitors shaft movement and provides measurement information to a compatible monitoring system.

The monitoring equipment can compare measured values against configured alarm and trip thresholds. If the measured displacement or vibration exceeds the established limits, the system can notify operators or initiate an appropriate protective response.

The alarm and trip functions depend on the complete monitoring system, not on the sensor alone.

PLC and DCS Integration

A distributed control system or programmable logic controller may receive processed measurement signals from the machinery monitoring equipment.

These signals can be used for equipment status displays, alarm handling, process coordination, and maintenance records.

The PR6424 probe itself should not be treated as a direct PLC input device without the required compatible signal-conditioning equipment.

Condition Monitoring

Continuous shaft measurement helps maintenance teams understand how machinery behaves under different operating conditions.

By comparing current measurements with historical trends, engineers can identify changes that may be associated with mechanical deterioration.

This information can support condition-based maintenance and help reduce unnecessary equipment shutdowns.

Industrial Applications

The Epro PR6424/106-000 is part of a sensor family designed for critical rotating machinery applications.

1. Steam Turbines

Steam turbines operate under demanding mechanical and thermal conditions. Shaft movement and vibration are important parameters for evaluating rotor stability and bearing performance.

The PR6424 series can be used to measure radial and axial shaft displacement in suitable turbine monitoring arrangements.

Continuous measurements help operators monitor changes in rotor behavior and identify abnormal mechanical conditions.

2. Gas Turbines

Gas turbines require reliable machinery monitoring because unexpected mechanical problems can affect production availability and operating safety.

Eddy current probes can measure shaft movement without contacting the rotating surface. The resulting data can be used by compatible monitoring equipment to evaluate vibration and shaft position.

3. Hydro Turbines and Generators

Hydroelectric generating equipment contains large rotating assemblies that require continuous condition monitoring.

The PR6424 series can be applied to suitable shaft-monitoring points to measure displacement and vibration-related movement.

These measurements help maintenance teams assess rotor behavior and monitor changes during different operating conditions.

4. Industrial Compressors

Large compressors are commonly used in chemical processing, petrochemical facilities, gas transportation, and industrial manufacturing.

Shaft displacement monitoring helps engineers evaluate the mechanical condition of rotating assemblies and identify unusual movement.

A non-contact sensor is useful where the rotating shaft must be monitored continuously without physical interference.

5. Industrial Pumps

Critical industrial pumps may operate continuously in demanding process environments. Changes in shaft vibration and position can indicate mechanical wear, bearing problems, or alignment issues.

The PR6424 series can support monitoring arrangements designed for suitable pump shaft dimensions and target materials.

6. Industrial Fans

Large industrial fans and blowers may operate under variable loads and continuous production conditions.

Shaft vibration monitoring can help identify mechanical changes caused by imbalance, bearing deterioration, or looseness.

The sensor provides displacement information that can be processed by a compatible monitoring system.

Installation and System Integration

Correct installation is essential for reliable measurement. The probe must be mounted securely, positioned correctly, and connected to compatible signal-conditioning equipment.

1. Verify Sensor Compatibility

Before installation, confirm that the PR6424/106-000 is compatible with the intended signal converter and monitoring system.

The sensor and converter must be designed to work together. Check the applicable electrical characteristics, cable arrangement, connector type, and calibration requirements.

Do not assume that every PR6424 probe variant is interchangeable simply because it belongs to the same product family.

2. Prepare the Mounting Location

The probe should be installed at a suitable measurement position near the rotating shaft.

The mounting arrangement must provide sufficient mechanical stability and maintain the specified clearance between the sensor head and the target surface.

The PR6424 series uses an M18 × 1.5 mounting thread in its published mechanical configuration. Verify the exact mechanical details of the /106-000 variant before preparing the mounting location.

3. Set the Initial Air Gap

The nominal center air gap for the PR6424 series is approximately 2.7 mm.

Correct gap adjustment is important because the sensor’s output depends on the distance between the probe tip and the target surface.

The initial gap should be established using the manufacturer’s installation procedure and the compatible converter’s calibration requirements.

Incorrect positioning may cause inaccurate measurements or reduce the available linear operating range.

4. Check the Target Material

The PR6424 series is specified for measurement against ferromagnetic steel, with 42CrMo4 identified as the standard reference material.

Target material affects the electromagnetic response of an eddy current sensor. Therefore, shaft material and surface characteristics should be considered during installation and calibration.

Using an unsuitable target material may affect measurement accuracy.

5. Protect the Sensor Cable

The sensor cable should be routed away from sources of mechanical damage, excessive heat, and electrical interference.

Avoid sharp bends, crushing, or excessive pulling forces. Follow the specified minimum bending radius for the exact cable configuration.

Where armored and non-armored cable versions are available, confirm the actual version before planning the installation route.

6. Connect the Signal Converter

The sensor should be connected to a compatible EPRO signal converter or approved monitoring interface.

The converter processes the sensor’s electrical response and provides a measurement signal for the machinery monitoring system.

Verify connector compatibility, cable length, electrical characteristics, and calibration settings before energizing the system.

7. Commission the Measurement System

After installation, establish the correct air gap and verify the sensor output across the intended operating range.

Check that the monitoring system displays a stable measurement under normal machine conditions. Confirm alarm thresholds and protective functions according to the machinery protection design.

Record the installed probe model, converter configuration, cable details, and commissioning values for future maintenance.

Compatible System Components

The PR6424/106-000 is normally used as part of a complete eddy current measurement chain.

These are functional system components, not a statement that all items are supplied with the sensor. Confirm the actual bill of materials before purchasing.

Alternative Models and Replacement Considerations

The PR6424 family includes multiple 16 mm eddy current sensor variants. Although they share a common measurement technology, differences in cable construction, cable length, connector arrangement, and mounting configuration may affect interchangeability.

Before replacing the PR6424/106-000, compare the following:

• Complete model and ordering code.
• Sensor head diameter.
• Mounting thread and mechanical dimensions.
• Cable length and construction.
• Connector and adapter arrangement.
• Target material and shaft dimensions.
• Sensitivity and linearity.
• Measurement range.
• Operating temperature limits.
• Compatibility with the installed signal converter.
• Calibration and monitoring-system settings.

A replacement probe should be treated as a complete measurement-chain decision. Matching only the 16 mm sensor diameter is not sufficient to guarantee compatibility.

Key Advantages

Non-Contact Measurement

The sensor measures shaft displacement without physical contact. This reduces mechanical wear at the sensing point and supports continuous monitoring of rotating machinery.

16 mm Sensing Head

The 16 mm sensor head is designed for applications requiring a larger sensing diameter within the PR6424 product family.

High Measurement Sensitivity

The typical sensitivity of 4 V/mm provides a defined relationship between shaft displacement and sensor output.

Static and Dynamic Measurement

The PR6424 series supports both static position measurement and dynamic displacement measurement, making it suitable for different machinery monitoring requirements.

Industrial Machinery Applications

The sensor family is designed for critical rotating equipment, including turbines, compressors, pumps, and fans.

Stainless Steel Sleeve

The stainless steel sleeve provides a robust mechanical structure for industrial sensor installation.

PTFE Cable Material

The published PR6424 specifications identify PTFE as the cable material, supporting use in demanding industrial temperature environments within the applicable cable limits.

Condition Monitoring Support

Continuous displacement measurements can help maintenance personnel identify changes in machinery behavior and plan inspections or maintenance activities.

Technical FAQs

1. What is the Epro PR6424/106-000?

The Epro PR6424/106-000 is a 16 mm eddy current sensor from the Emerson EPRO PR6424 family. It is designed for non-contact measurement of shaft displacement and vibration in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm, as indicated by the PR6424 product-family specification.

3. What is the measurement principle?

It uses electromagnetic eddy-current technology. The probe generates an alternating electromagnetic field, and the electrical response changes when the distance to a conductive target changes.

4. What is the typical sensitivity?

The PR6424 series has a typical sensitivity of 4 V/mm, equivalent to approximately 101.6 mV/mil.

5. What is the static measurement range?

The published PR6424 series static measurement range is ±2.0 mm. The usable range in an installation depends on the initial air gap, target material, converter, and calibration.

6. What is the dynamic measurement range?

The published dynamic measurement range is 0 to 1,000 μm. This is used for monitoring dynamic shaft movement and vibration-related displacement.

7. Which target materials can be measured?

The PR6424 series is specified for ferromagnetic steel, with 42CrMo4 identified as the standard reference target material.

8. Does the sensor require a signal converter?

Yes. The probe is normally used with a compatible signal converter that processes its electrical response and produces a usable measurement signal for monitoring equipment.

9. What is the weight of the PR6424 sensor?

The supplied listing weight is 0.2 kg. The PR6424 family specification sheet lists approximately 200 g for the sensor with a 1 m cable and without armor.

10. Can the PR6424/106-000 replace another PR6424 model?

Not automatically. Different variants may have different cable lengths, connectors, adapters, and mounting configurations. Confirm the complete ordering code and converter compatibility before replacement.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/106-000, verify the complete model designation and inspect the sensor’s physical condition. Pay particular attention to the sensing tip, threaded sleeve, cable insulation, connector, and identification markings.

For replacement projects, compare the probe with the installed unit rather than relying only on the product-family name. Cable length, connector arrangement, mounting dimensions, and converter compatibility can all affect whether the replacement will operate correctly.

If the sensor is supplied as part of an existing machinery protection system, confirm that the signal converter is suitable for the replacement probe. Check the required calibration procedure and retain the original configuration records wherever possible.

During routine maintenance, inspect the cable for cuts, abrasion, excessive bending, or damage caused by vibration. Check the mounting hardware and ensure that the probe remains securely positioned.

Changes in measurement output should be evaluated in relation to machine operating conditions. A sudden change in shaft displacement may indicate a mechanical issue, but the sensor installation, cable, converter, and monitoring system should also be checked before drawing conclusions.

For critical turbines, compressors, and generators, follow the plant’s machinery protection procedures and the manufacturer’s technical documentation when testing or replacing the sensor.

Conclusion

The Epro PR6424/106-000 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement and vibration in critical rotating machinery. As part of the Emerson EPRO PR6424 family, it supports static position measurement and dynamic displacement monitoring in applications such as steam turbines, gas turbines, generators, compressors, pumps, and industrial fans.

With a typical sensitivity of 4 V/mm, a static measurement range of ±2.0 mm, and a dynamic measurement range of up to 1,000 μm, the PR6424 family provides measurement capabilities for machinery condition-monitoring systems.

For installation and replacement, the complete sensor configuration must be verified. Correct cable selection, connector compatibility, initial air-gap adjustment, target material, and signal-converter matching are essential for reliable measurement performance.