Product Overview

The EPRO PR6424/103-101 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the mechanical condition of rotating machinery. Developed for industrial machinery protection and condition monitoring applications, it belongs to the PR6424 series of 16 mm eddy current probes associated with Emerson EPRO equipment.

The sensor measures the distance between its probe tip and a conductive target, typically a rotating shaft. By continuously detecting changes in this gap, it can provide information about shaft vibration, radial and axial displacement, shaft position, eccentricity, and rotational behavior. Because the measurement is non-contact, the probe can monitor a rotating component without physically touching the shaft during normal operation.

The PR6424 series is commonly associated with critical rotating equipment such as steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. These machines often operate under demanding mechanical and thermal conditions. Continuous monitoring of shaft movement can help operators identify abnormal vibration, changes in operating clearances, and developing mechanical problems.

The PR6424/103-101 has a specified sensor head diameter of 16 mm and a supplied weight of approximately 0.2 kg. Its compact probe design allows it to be installed at designated measurement locations near a rotating shaft, provided that the mounting arrangement and clearance requirements are satisfied.

The sensor operates as part of a compatible measurement chain. It is normally connected to a suitable signal converter or driver, which processes the probe’s electrical response and provides a measurement signal to a machinery protection or monitoring system. The probe, extension cable, converter, and monitoring input must be compatible and correctly calibrated.

For maintenance and replacement projects, the complete model number is important. PR6424 probes may have different cable lengths, connector arrangements, mounting configurations, and other variant-specific details. The suffix /103-101 should therefore be checked against the actual product label and the installed measurement system before ordering.

Technical Specifications

Note: The performance figures above describe the PR6424 sensor family. Confirm the exact cable, connector, mounting, temperature, and calibration configuration for PR6424/103-101 before installation or replacement.

Function and Working Principle

The PR6424/103-101 uses the eddy current measurement principle. This technology is widely used in machinery monitoring because it can measure the position and movement of a conductive target without requiring physical contact.

1. Electromagnetic Field Generation

The sensor contains an electromagnetic coil near its measuring tip. When supplied with the appropriate excitation signal from a compatible converter, the coil generates an alternating electromagnetic field.

This field extends from the probe tip toward the surface of the target shaft. The sensor is positioned at a controlled distance from the shaft so that changes in the gap can be detected within the probe’s calibrated measurement range.

2. Eddy Current Formation

When the electromagnetic field reaches a conductive target, such as a ferromagnetic steel shaft, circulating electrical currents are induced in the target surface. These currents are known as eddy currents.

The strength and distribution of the eddy currents depend on the distance between the probe and the target, as well as the target material and other measurement conditions.

As the shaft moves closer to or farther away from the sensor, the electromagnetic interaction changes. This changes the electrical characteristics of the probe coil.

3. Signal Conversion

The electrical response of the probe is processed by a compatible signal converter. The converter translates the change in probe impedance into a usable output signal related to the distance between the sensor tip and the shaft.

For the PR6424 series, the typical sensitivity is 4 V/mm when operating with the specified reference target and compatible measurement chain.

The converter output can then be supplied to a machinery monitoring system for display, recording, alarm generation, and protection functions.

4. Shaft Displacement Measurement

The sensor can detect static and dynamic changes in the distance between the probe and the shaft.

Static measurements are useful for monitoring shaft position and operating clearance. Dynamic measurements are used to identify shaft movement caused by vibration, imbalance, misalignment, or other mechanical conditions.

The PR6424 series has a nominal static measurement range of ±2.0 mm and a dynamic range of 0–1,000 μm, subject to the specified measurement configuration.

5. Continuous Condition Monitoring

When installed at suitable measurement points, multiple probes can monitor different aspects of rotating machinery behavior.

For example, two probes positioned at different angular locations around a shaft can provide information about radial vibration. Axial probes can be used to monitor shaft thrust position where the machine design and monitoring system support this arrangement.

The resulting signals help maintenance personnel evaluate machine behavior and identify changes that may require further inspection.

Role in Industrial Machinery Protection Systems

The PR6424/103-101 is a sensing component rather than a standalone machinery protection controller. Its measurement data becomes useful for plant monitoring when the probe is connected to a compatible converter and monitoring system.

Shaft Vibration Monitoring

Shaft vibration is an important condition indicator for turbines, compressors, pumps, and other rotating equipment. Changes in vibration amplitude or behavior may indicate mechanical imbalance, misalignment, bearing-related problems, or changes in operating conditions.

The eddy current sensor provides non-contact displacement information that can be processed by the monitoring system.

Axial Position Monitoring

Axial movement monitoring is important for machinery where the shaft must remain within a defined thrust position range. Excessive axial displacement may indicate thrust-bearing problems or other mechanical conditions requiring investigation.

A suitable probe installation can provide the displacement signal used by the monitoring system to evaluate shaft position.

Shaft Eccentricity Measurement

Shaft eccentricity describes the deviation of a shaft’s geometric center from its expected rotational center. Monitoring eccentricity can help maintenance teams assess shaft condition and identify changes in mechanical alignment or geometry.

The PR6424 series can support eccentricity measurement when the sensor arrangement, calibration, and monitoring system are correctly configured.

Speed and Key-Related Measurements

Eddy current probes can also be used in suitable arrangements to detect shaft features or reference marks. These signals can support speed-related monitoring and rotational reference measurements.

The exact application depends on the probe installation, target geometry, converter configuration, and monitoring-system capability.

Machinery Protection Integration

The probe’s measurement signal can be incorporated into a machinery protection system. The monitoring system evaluates the signal against configured alarm and trip limits and can communicate abnormal conditions to the plant control system.

The sensor itself does not independently decide whether a machine should trip. That function belongs to the connected monitoring and protection architecture.

Industrial Applications

The PR6424 16 mm eddy current sensor family is designed for critical rotating machinery. Its non-contact measurement principle is particularly useful where shaft movement must be monitored continuously.

1. Steam Turbines

Steam turbines operate at high rotational speeds and are often essential to power generation and industrial processes. Monitoring shaft vibration and axial position helps operators evaluate mechanical behavior during startup, normal operation, and changing load conditions.

The PR6424 series can be used at suitable turbine measurement locations as part of a compatible machinery monitoring arrangement.

2. Gas Turbines

Gas turbines operate under demanding thermal and mechanical conditions. Shaft vibration and displacement measurements provide important information for evaluating rotor behavior and machinery condition.

A properly installed eddy current sensor can supply non-contact shaft movement data to the monitoring system.

3. Hydro Turbines

Hydro turbines are used in power-generation facilities and may operate continuously under varying load conditions. Shaft displacement and vibration monitoring can help identify changes in rotating assembly behavior.

The sensor can be incorporated into suitable measurement points where the shaft material, clearance, and installation geometry meet the probe requirements.

4. Industrial Compressors

Compressors are used in petrochemical plants, refineries, gas processing facilities, and general manufacturing. Their rotating assemblies require reliable monitoring because excessive vibration or shaft displacement may affect equipment availability.

Eddy current probes can provide information about shaft movement for use in compressor protection and condition monitoring systems.

5. Centrifugal Pumps

Large industrial pumps may operate continuously in water treatment, chemical processing, power generation, and oil and gas facilities.

Monitoring shaft vibration and position can help maintenance teams detect changes in mechanical condition. The probe must be installed at an appropriate measurement location and connected to a compatible signal-conditioning system.

6. Industrial Fans

Large fans used in ventilation, combustion air, and process-gas systems may require continuous vibration monitoring. Non-contact displacement measurement can provide useful information about shaft movement during operation.

The PR6424 series may be used where the fan’s shaft dimensions, target material, and measurement requirements are compatible with the sensor.

Installation and System Integration

Correct installation is essential for accurate measurements. Even a high-performance sensor may produce unreliable data if the probe is incorrectly positioned, poorly secured, or connected to an incompatible converter.

1. Verify the Exact Sensor Configuration

Before installation, confirm the complete model number PR6424/103-101. Check the probe’s cable length, connector type, mounting arrangement, and other mechanical details against the existing installation.

Do not assume that all PR6424 probes use identical cable and connector configurations. A replacement must match the requirements of the installed measurement chain.

2. Confirm Target Material

The PR6424 series is calibrated using a specified ferromagnetic steel reference material, typically 42CrMo4.

The target material affects the electromagnetic response of the probe. If the actual shaft material differs from the reference material, the measurement accuracy may be affected.

Confirm the shaft material and the calibration requirements before commissioning.

3. Check the Probe-to-Shaft Gap

The sensor must be installed with the correct distance between its tip and the target shaft. The PR6424 series has a nominal center air gap of approximately 2.7 mm.

The final installation gap should follow the applicable sensor and converter documentation. An incorrect gap can reduce measurement range or cause the output to operate outside its calibrated linear region.

4. Mechanical Mounting

The sensor should be mounted securely using the designated installation arrangement. The probe must not move during normal machine operation.

Ensure that the probe tip has sufficient clearance from the shaft under all expected operating conditions. Consider shaft thermal expansion, vibration amplitude, mechanical tolerances, and installation alignment.

5. Cable Routing

Route the sensor cable according to the manufacturer’s instructions. Avoid unnecessary sharp bends, excessive tension, and locations where the cable may be exposed to mechanical damage.

Keep the sensor wiring appropriately separated from high-power conductors and sources of electrical interference. Confirm the connector and cable configuration before connecting the probe to the converter.

6. Converter and Monitoring-System Compatibility

The sensor must be paired with a compatible signal converter or driver. Verify the sensor model, cable configuration, converter type, and calibration requirements.

The converter output must also be compatible with the receiving machinery monitoring system. Do not connect the probe directly to an arbitrary PLC analog input unless the required signal conditioning and electrical interface are provided.

7. Commissioning and Functional Checks

After installation, verify the probe gap, mechanical security, cable condition, and connector engagement.

Check the converter output and confirm that the measurement changes in the expected direction when the target distance changes. Compare the output with the expected calibration behavior and confirm that the monitoring system displays reasonable values.

Alarm and trip settings should be verified as part of the overall machinery protection commissioning process.

Compatible System Components

The PR6424/103-101 normally operates as part of a complete machinery monitoring chain.

These components are examples of a typical measurement arrangement. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 belongs to the EPRO PR642x family of eddy current sensors. Other models in the family may have different measuring ranges, sensitivities, sensor diameters, and installation characteristics.

Before selecting a replacement, check:

• Complete sensor model number.
• Probe head diameter and mechanical dimensions.
• Cable length and cable construction.
• Connector type and pin arrangement.
• Sensor thread and mounting arrangement.
• Target shaft material and diameter.
• Static and dynamic measurement ranges.
• Sensitivity and calibration.
• Operating temperature requirements.
• Compatible signal converter.
• Monitoring-system input and configuration.

A replacement probe must match the installed measurement chain. Using a sensor with a different sensitivity or calibration may result in incorrect displacement readings and unreliable alarm thresholds.

Key Advantages

Non-Contact Measurement

The sensor measures shaft displacement without physical contact during normal operation. This avoids the mechanical wear associated with contact-based measurement methods.

Continuous Shaft Monitoring

The probe can provide continuous measurement data for rotating machinery when connected to a compatible converter and monitoring system.

High Measurement Sensitivity

The PR6424 series has a typical sensitivity of 4 V/mm, supporting the detection of relatively small changes in probe-to-shaft distance.

Static and Dynamic Measurement

The sensor family supports both static position measurement and dynamic displacement measurement, making it useful for several machinery monitoring tasks.

Industrial Machinery Applications

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

Compact Probe Design

The 16 mm sensor head provides a compact measurement interface for installations where available mounting space is limited.

Integration with Machinery Protection Systems

When paired with compatible signal-conditioning and monitoring equipment, the probe can contribute to vibration monitoring, shaft-position measurement, and machinery protection functions.

Technical FAQs

1. What is the EPRO PR6424/103-101?

The EPRO PR6424/103-101 is a 16 mm eddy current sensor designed for non-contact measurement of shaft displacement and movement in rotating machinery.

2. What is the main function of this sensor?

Its main function is to measure the distance between the probe tip and a conductive target. The resulting signal can be used to monitor shaft vibration, radial or axial displacement, position, eccentricity, and other suitable machinery parameters.

3. What is the sensor head diameter?

The specified sensor head diameter is 16 mm.

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

The typical sensitivity is 4 V/mm when used with the specified reference target and compatible measurement chain. The actual measurement performance depends on calibration and installation.

5. What is the measurement range?

The PR6424 series has a nominal static measurement range of ±2.0 mm and a dynamic measurement range of 0–1,000 μm. Confirm the exact measurement configuration before applying these values to a specific installation.

6. What is the nominal center air gap?

The nominal center air gap is approximately 2.7 mm for the PR6424 series. The final installation gap must follow the applicable probe and converter documentation.

7. Which materials can the sensor measure?

The PR6424 series is specified for conductive targets and uses ferromagnetic steel, typically 42CrMo4, as its standard reference material. Target material differences can affect calibration and measurement accuracy.

8. Does the sensor work independently?

No. It normally requires a compatible signal converter or driver to excite the probe and process its measurement response. The resulting signal is then connected to a suitable monitoring system.

9. Where is the PR6424 series commonly used?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. These installations use the sensor for shaft displacement and vibration monitoring.

10. What should be checked before replacing a PR6424/103-101?

Confirm the complete model number, sensor dimensions, cable length, connector, mounting arrangement, target material, converter compatibility, and calibration requirements. These details are essential for maintaining accurate measurements.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/103-101, verify the complete model number on the product label. The PR6424 family includes multiple variants, and differences in cable configuration, connector arrangement, and mechanical construction may affect compatibility.

For replacement projects, compare the existing sensor with the proposed unit before installation. Check the probe diameter, mounting thread, cable length, connector, and required measurement range. Confirm that the existing converter supports the replacement sensor and its calibration.

During routine maintenance, inspect the sensor cable for cuts, abrasion, excessive bending, and signs of heat damage. Check the mounting hardware and ensure that the probe remains securely positioned. Contamination or mechanical damage near the sensor tip should be addressed according to the applicable maintenance instructions.

It is also important to preserve the original measurement configuration. Record the probe model, converter model, calibration information, installation gap, and monitoring-channel settings. These records can help maintenance personnel troubleshoot measurement deviations and replace components correctly.

For critical rotating equipment, sensor replacement should be followed by functional verification of the complete measurement chain. Confirm the signal response, measurement scaling, alarm settings, and monitoring-system operation before returning the machinery to normal service.

Conclusion

The EPRO PR6424/103-101 16 mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in critical rotating machinery. Its 16 mm probe head and eddy current operating principle make it suitable for monitoring applications involving turbines, compressors, pumps, fans, and other industrial rotating equipment.

The PR6424 family provides a typical sensitivity of 4 V/mm, a static measurement range of ±2.0 mm, and a dynamic measurement range of 0–1,000 μm. These capabilities support shaft position and vibration monitoring when the probe is correctly installed and paired with a compatible signal converter.

For maintenance and replacement applications, accurate model identification is essential. Verifying the /103-101 suffix, cable configuration, connector, mounting details, target material, and converter compatibility helps maintain reliable measurement performance in industrial machinery protection systems.