Introduction

The EPRO PR6424/104-000 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the condition and operating behavior of rotating machinery. As part of the EPRO PR6424 sensor family from Emerson, it is used in machinery protection and condition-monitoring applications where accurate measurement of shaft movement, vibration, and position is important.

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 particularly suitable for monitoring high-speed shafts in turbines, compressors, pumps, generators, and other critical rotating equipment.

The PR6424 series uses a nominal 16 mm sensing head and is designed to provide dynamic and static displacement measurements. When connected to a compatible signal converter and monitoring system, the probe can provide information about shaft vibration, axial position, radial displacement, eccentricity, and related machine conditions.

The PR6424/104-000 is identified as a 16 mm eddy current sensor. Its supplied listing weight is 0.2 kg. The exact cable length, connector arrangement, thread configuration, and converter compatibility should be confirmed from the individual product label and associated system documentation before installation.

Product Overview

The EPRO PR6424/104-000 is intended for non-contact measurement in industrial machinery monitoring systems. Its sensing principle is based on electromagnetic induction. An alternating electromagnetic field is generated at the probe tip, and the presence of a suitable conductive target changes the electrical characteristics of the sensor circuit.

The resulting signal can be processed by a compatible EPRO signal converter. The converter conditions the measurement and provides an output that can be interpreted by machinery protection equipment, vibration monitoring systems, or other suitable monitoring devices.

The PR6424 family is commonly used in critical turbomachinery applications. Typical monitored machines include steam turbines, gas turbines, hydro turbines, centrifugal compressors, industrial pumps, and fans.

The 16 mm sensing head is intended for applications where the installation geometry and shaft dimensions are suitable for this probe size. The sensor must be installed with the correct initial gap and positioned relative to an appropriate ferromagnetic target surface.

For reliable measurements, the probe, extension cable, signal converter, and monitoring equipment must be treated as a coordinated measurement chain. Using an incompatible converter or an incorrectly matched cable can affect signal accuracy and measurement stability.

Technical Specifications

Note: The electrical and performance values above are PR6424 family reference specifications. Confirm the exact PR6424/104-000 configuration, cable arrangement, operating temperature limits, and converter compatibility against the unit’s documentation before use.

Function and Working Principle

The PR6424/104-000 operates through the eddy current measurement principle. It detects changes in the distance between the probe tip and a conductive target by monitoring changes in the electromagnetic field generated by the sensing coil.

1. Electromagnetic Field Generation

An alternating electrical signal is applied to the sensing circuit inside the probe. This produces an electromagnetic field around the sensing tip.

When a suitable conductive target, such as a ferromagnetic steel shaft, approaches the probe, the field induces eddy currents in the target surface.

2. Displacement Detection

The induced eddy currents affect the electromagnetic characteristics of the probe. Changes in the distance between the probe and the target cause corresponding changes in the sensor’s electrical response.

The sensor system uses this relationship to determine the relative position of the shaft surface.

Because the probe does not need to touch the rotating shaft, it can monitor movement continuously without introducing mechanical contact between the sensing element and the machine.

3. Signal Conversion

The probe is normally used with a compatible signal converter. The converter processes the probe’s electrical response and produces a conditioned output suitable for monitoring equipment.

The complete measurement chain generally includes:

• PR6424 eddy current probe.
• Compatible extension cable, where required.
• Matching signal converter.
• Machinery monitoring or protection system.

The exact combination must follow the manufacturer’s compatibility requirements. Probe and converter models should not be mixed solely because they belong to the same product family.

4. Static and Dynamic Measurement

The PR6424 series supports both static and dynamic measurement.

Static measurement is useful for observing shaft position and slow changes in relative displacement. Dynamic measurement is used to monitor rapid shaft movement, including vibration during machine operation.

These measurements can help operators identify changes in bearing behavior, rotor position, mechanical alignment, and overall machine condition.

Role in Industrial Machinery Monitoring Systems

The PR6424/104-000 can serve as a sensing component within a machinery condition-monitoring architecture. It provides measurement information that can be processed by signal-conditioning and monitoring equipment.

Shaft Vibration Monitoring

Shaft vibration is an important indicator of rotating machinery condition. Changes in vibration amplitude or behavior may be associated with rotor imbalance, misalignment, mechanical looseness, bearing-related problems, or other operating abnormalities.

The sensor provides non-contact displacement information that can be used by a compatible monitoring system to evaluate shaft vibration.

Axial Position Monitoring

Axial displacement measurement helps monitor the movement of a rotating shaft along its longitudinal axis.

In turbines and compressors, excessive axial movement may indicate changes in thrust-bearing behavior or other mechanical conditions. A properly installed sensor can provide position information for machinery monitoring and protection.

Radial Shaft Displacement

Radial displacement monitoring measures movement perpendicular to the shaft axis. This information is useful for evaluating rotor behavior relative to the probe mounting position.

In many installations, multiple probes are positioned around the shaft to provide information about radial movement in different directions.

Integration with Monitoring Equipment

The sensor is not normally used as a standalone display device. Its output must be processed by a compatible signal converter and monitoring system.

The monitoring architecture may include vibration monitoring modules, machinery protection equipment, alarm systems, and plant control interfaces. The exact equipment depends on the installed EPRO or Emerson monitoring platform.

Industrial Applications

1. Steam Turbines

Steam turbines operate under demanding mechanical and thermal conditions. Shaft displacement and vibration monitoring are important for evaluating rotor behavior and identifying abnormal operating conditions.

The PR6424 series can be used in suitable turbine installations to monitor relative shaft movement and provide measurement signals to machinery protection equipment.

2. Gas Turbines

Gas turbines require continuous monitoring of critical rotating components. Shaft vibration and position measurements can support condition assessment during startup, normal operation, and shutdown.

A properly configured eddy current measurement system can help maintenance teams identify changes in rotor behavior.

3. Industrial Compressors

Centrifugal compressors are widely used in petrochemical plants, refineries, gas processing facilities, and other industrial operations.

The PR6424 sensor family can be applied to suitable compressor shafts for monitoring radial displacement, axial position, and dynamic vibration.

4. Pumps and Pumping Systems

Large industrial pumps often operate continuously and may be exposed to changing process loads. Shaft vibration monitoring can help identify developing mechanical problems.

The sensor can provide displacement information for compatible pump-monitoring installations, particularly where non-contact shaft measurement is required.

5. Hydro Turbines and Generators

Hydro turbines and generators contain large rotating assemblies that require reliable condition monitoring. Shaft movement and vibration measurements can help assess rotor behavior and support maintenance planning.

The PR6424 family is suitable for selected applications where the probe geometry, shaft material, and measurement requirements match the system specifications.

6. Industrial Fans

Large industrial fans are used in power generation, cement production, metallurgy, and process ventilation systems.

Monitoring shaft displacement can help identify changes in rotating behavior and provide useful information for preventive maintenance programs.

Installation and System Integration

Correct installation is essential for obtaining stable and repeatable measurements from the PR6424/104-000.

1. Verify Probe Configuration

Before installation, confirm the full model number and inspect the probe assembly. Check the sensing head, cable, connector, thread, and mounting dimensions.

The suffix of an EPRO probe model can identify a particular mechanical or electrical configuration. Do not assume that every PR6424 probe has the same cable length, connector, or mounting arrangement.

2. Check the Target Surface

The PR6424 series reference specifications use ferromagnetic steel, with 42CrMo4 commonly identified as the standard target material.

Target material affects the electrical response of an eddy current sensor. If the shaft material differs from the reference material, the measurement system may require appropriate calibration or correction.

The target surface should also be suitable for stable measurement. Excessive surface irregularities, deposits, or mechanical damage can affect measurement quality.

3. Set the Initial Air Gap

The probe must be positioned at the correct distance from the shaft surface. The PR6424 series has a nominal center air gap of approximately 2.7 mm.

The final gap should be established according to the applicable probe and converter documentation. Incorrect positioning can reduce the available measurement range or cause the output to operate outside its intended linear region.

4. Secure the Probe

Install the probe using the correct mounting arrangement and thread specification for the exact variant.

The mounting structure should be rigid enough to prevent unwanted movement during machine operation. Probe movement caused by a loose bracket can be interpreted as shaft displacement and may produce misleading monitoring data.

5. Connect the Measurement Chain

Connect the probe to the correct extension cable and signal converter, if required. Confirm connector compatibility, cable condition, grounding, and routing.

Keep sensor cables away from high-current conductors and sources of electromagnetic interference where practical. Follow the manufacturer’s cable routing and shielding requirements.

6. Calibrate and Verify the Signal

After installation, verify the initial gap and check the measurement output using the appropriate converter or monitoring equipment.

Confirm that the signal responds correctly to changes in probe-to-target distance. Review the output range, polarity, scaling, and alarm settings before placing the machine into normal service.

Compatible System Components

A complete PR6424 measurement installation typically requires several coordinated components.

A compatible converter is essential for reliable operation. The PR6424 probe should be treated as part of a complete measurement system rather than as an independent sensor with a universal output.

Advantages of the PR6424/104-000

Non-Contact Measurement

The eddy current principle allows shaft displacement to be measured without physical contact. This is particularly valuable for rotating machinery where continuous contact measurement would be impractical.

16 mm Sensing Head

The 16 mm sensing head is designed for suitable industrial shaft-monitoring installations. Its size supports applications requiring a probe with a larger sensing diameter than smaller eddy current probe families.

Static and Dynamic Measurement

The PR6424 family supports both static displacement and dynamic vibration measurement. This allows a single measurement technology to contribute to several machinery monitoring functions.

High Measurement Sensitivity

The family reference sensitivity of 4 V/mm supports the measurement of relatively small changes in probe-to-target distance when used with a compatible converter.

Industrial Machinery Applications

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

Integration with Condition Monitoring Systems

When paired with the correct converter and monitoring equipment, the probe can contribute to centralized machinery condition monitoring and protection.

Compact Sensor Construction

The supplied sensor weight of 0.2 kg makes it a relatively compact component for industrial machinery instrumentation. The actual installation arrangement depends on the probe’s cable and mounting configuration.

Technical FAQs

1. What is the EPRO PR6424/104-000?

The PR6424/104-000 is identified as a 16 mm eddy current sensor used for non-contact measurement of displacement in rotating machinery. It belongs to the EPRO PR6424 sensor family.

2. What is the main function of this sensor?

Its primary function is to measure the distance between the probe tip and a conductive target without physical contact. In machinery monitoring systems, this measurement can be used to evaluate shaft vibration, radial displacement, axial position, and other movement-related conditions.

3. What is the sensor head diameter?

The sensor head diameter is 16 mm, consistent with the PR6424 product family.

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

The published family reference sensitivity is 4 V/mm. The applicable sensitivity and calibration should be confirmed for the complete probe and converter combination.

5. What is the static measurement range?

The PR6424 family has a reference static measurement range of ±2.0 mm. This represents the specified displacement range around the calibrated operating point.

6. What is the dynamic measurement range?

The family reference dynamic range is 0–1,000 μm peak-to-peak. Actual usable performance depends on the measurement chain, installation, and operating conditions.

7. Does the sensor require a signal converter?

A compatible signal converter is normally required to condition the probe signal for use by machinery monitoring equipment. The converter must match the probe’s electrical configuration.

8. What machines can use the PR6424 sensor?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, industrial pumps, generators, and fans. Suitability depends on shaft geometry, target material, temperature, and monitoring requirements.

9. What is the weight of the PR6424/104-000?

The supplied product listing weight is 0.2 kg. A PR6424 family specification also gives approximately 200 grams for the sensor with a 1-meter cable and without armor. The actual weight may vary with cable length and construction.

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

Confirm the full model number, sensing head diameter, cable length, connector, mounting thread, probe dimensions, converter compatibility, and calibration requirements. A probe with the same 16 mm diameter is not necessarily an electrically or mechanically interchangeable replacement.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/104-000, verify the complete model number and compare it with the identification label on the installed sensor. The PR6424 family includes multiple mechanical and cable configurations, so the product description alone may not provide enough information to establish interchangeability.

For replacement projects, confirm the probe’s cable length, connector type, mounting thread, sensing head dimensions, and compatibility with the installed signal converter. Also verify whether the required extension cable or mounting accessories are included.

During routine maintenance, inspect the sensor cable for abrasion, excessive bending, damaged insulation, or loose connections. Check that the probe mounting remains secure and that the sensing tip is free from physical damage.

If the measurement output becomes unstable, inspect the complete measurement chain rather than replacing the probe immediately. Cable faults, connector contamination, incorrect air gap, target surface conditions, converter problems, and grounding issues can all affect measurement quality.

Keep records of the installed probe model, converter model, cable configuration, initial air gap, calibration information, and monitoring settings. This documentation can simplify future troubleshooting and reduce the risk of installing an incompatible replacement.

Conclusion

The EPRO PR6424/104-000 16 mm Eddy Current Sensor is designed for non-contact shaft displacement measurement in industrial rotating machinery. As part of the PR6424 family, it supports applications involving shaft vibration, radial and axial displacement, and machinery condition monitoring.

Its 16 mm sensing head and the family’s reference measurement characteristics make it suitable for selected turbine, compressor, pump, generator, and fan installations. With a supplied weight of 0.2 kg, it is a compact sensor component for industrial monitoring systems.

For reliable operation, the probe must be correctly matched with its extension cable, signal converter, target material, and monitoring equipment. Verifying the exact model configuration before installation or replacement is essential for maintaining measurement accuracy and machinery protection performance.