Product Overview

The Epro PR6424/105-030 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the condition and operating behavior of rotating industrial machinery. It belongs to the PR6424 sensor family from EPRO, now part of Emerson’s machinery health monitoring portfolio.

The sensor is designed to measure shaft movement without making physical contact with the rotating surface. It can be used to monitor radial and axial shaft displacement, vibration, shaft position, eccentricity, and speed-related characteristics when installed as part of a compatible measurement system.

Non-contact measurement is particularly important in high-speed rotating equipment. Physical contact between a sensor and a rotating shaft would introduce mechanical wear and could interfere with the measurement process. Eddy current technology avoids this problem by using an electromagnetic field to detect changes in the distance between the probe tip and a conductive target.

The PR6424 series has a nominal sensing-head diameter of 16 mm. Its published reference specifications include a sensitivity of 4 V/mm, linearity within ±1.5%, a static measuring range of ±2.0 mm, and a dynamic measurement range of 0 to 1,000 μm. These characteristics make the sensor suitable for machinery condition monitoring where accurate shaft movement information is required.

The PR6424/105-030 is intended for use in an appropriately configured measurement chain. A complete system normally includes the eddy current probe, a compatible extension cable where required, and a signal converter or monitoring instrument. The converter processes the probe signal and provides an output suitable for monitoring and protection equipment.

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. In these installations, shaft displacement and vibration measurements can help operators identify abnormal mechanical behavior and make informed maintenance decisions.

Technical Specifications

Note: The technical values above are PR6424 family reference specifications. Confirm the exact temperature range, cable construction, connector arrangement, thread, and compatibility of the PR6424/105-030 variant against its product label and applicable documentation.

Function and Working Principle

The PR6424/105-030 operates using the eddy current measurement principle. It generates an electromagnetic field at the probe tip and detects changes in that field when a conductive target moves closer to or farther away from the sensor.

This approach allows the system to measure shaft displacement without mechanical contact.

1. Electromagnetic Field Generation

The probe contains a sensing coil that produces a high-frequency electromagnetic field when connected to a compatible signal converter.

The field extends from the sensing tip toward the target surface. The sensor must be installed with an appropriate clearance so that the target remains within the specified measurement range.

2. Eddy Current Generation

When a conductive metal target enters the electromagnetic field, small circulating electrical currents called eddy currents are induced in the target material.

These currents affect the electromagnetic characteristics of the sensing coil. The resulting change in coil impedance is related to the distance between the probe and the target.

The measurement depends on the target material and surface characteristics. For this reason, the PR6424 series specifications refer to ferromagnetic steel, with 42CrMo4 used as the standard reference material.

3. Distance Measurement

The signal converter evaluates changes in the probe’s electrical response and translates them into a displacement-related output.

The published PR6424 reference sensitivity is 4 V/mm. Within the specified linear measuring range, changes in the probe-to-target gap correspond to proportional changes in output voltage.

A nominal center air gap of approximately 2.7 mm is specified for the series. Correct initial positioning is essential because an incorrect installation gap can reduce measurement accuracy or place the target outside the usable measuring range.

4. Vibration Measurement

When a rotating shaft moves because of vibration, the distance between the shaft surface and the probe changes continuously.

The sensor detects these variations and provides a signal that can be processed by a compatible monitoring instrument. The resulting data can be used to evaluate shaft vibration and identify changes in mechanical operating conditions.

5. Position and Displacement Monitoring

In addition to dynamic vibration, the PR6424 series can measure static shaft position within its specified range.

This is useful for monitoring axial movement, radial displacement, and other shaft-position characteristics. The measurement provides information that can help operators assess bearing behavior, alignment conditions, and changes in machinery operation.

Role in Industrial Machinery Monitoring Systems

The PR6424/105-030 is a sensing component rather than a complete machinery protection system. Its measurement signals are normally processed by compatible signal-conditioning and monitoring equipment.

Shaft Vibration Monitoring

Shaft vibration is an important indicator of rotating machinery condition. Changes in vibration amplitude may be associated with imbalance, misalignment, bearing problems, looseness, or other mechanical conditions.

A correctly installed PR6424 sensor can provide the displacement signal required by a compatible monitoring system to evaluate shaft vibration.

Axial Position Monitoring

Axial shaft movement can affect the operating condition of turbines, compressors, and other rotating machines.

The sensor can be installed to measure changes in the distance between the probe and an appropriate shaft target. Monitoring this movement helps maintenance personnel identify abnormal changes before they develop into more serious operating problems.

Eccentricity Measurement

Shaft eccentricity describes deviations in the shaft’s geometric position relative to its rotational center.

The PR6424 measurement principle allows the system to detect changes in the probe-to-shaft gap as the shaft rotates. These measurements can contribute to the assessment of shaft geometry and operating condition.

Integration with Machinery Protection Equipment

The sensor is typically connected to a compatible signal converter or monitoring module. The converter processes the raw probe response and provides a conditioned signal for machinery monitoring equipment.

Before installation, engineers should verify probe, extension cable, and converter compatibility. Using components from different measurement systems without checking their electrical characteristics can result in inaccurate measurements or an unusable signal.

Industrial Applications

The PR6424 series is intended for critical rotating machinery where continuous or periodic measurement of shaft displacement and vibration is important.

1. Steam Turbines

Steam turbines operate at high rotational speeds and require reliable monitoring of shaft movement.

The sensor can be used in suitable measurement arrangements to monitor radial shaft vibration, axial position, and eccentricity. These measurements help operators evaluate mechanical behavior during startup, normal operation, and shutdown.

2. Gas Turbines

Gas turbines are used in power generation and industrial mechanical-drive applications. Their rotating assemblies operate under demanding thermal and mechanical conditions.

A compatible PR6424 installation can provide shaft displacement information for machinery monitoring and protection systems. Probe temperature limits and installation requirements must be checked for the actual measurement location.

3. Hydro Turbines

Hydro turbines operate with rotating shafts, bearings, and supporting structures that require condition monitoring.

The sensor can help monitor shaft movement and vibration when installed with a suitable target surface and compatible signal-conditioning equipment.

4. Industrial Compressors

Centrifugal and other large industrial compressors rely on stable shaft operation. Changes in vibration and shaft position may indicate developing mechanical problems.

The PR6424 sensor can be incorporated into a monitoring arrangement to measure shaft displacement and provide data for condition assessment.

5. Pumps

Large industrial pumps are commonly used in water treatment, chemical processing, power plants, and manufacturing facilities.

Where shaft monitoring is required, the sensor can provide non-contact displacement information. This is particularly useful for equipment that operates continuously or has significant maintenance and production consequences if an unexpected shutdown occurs.

6. Industrial Fans

Large fans and ventilation systems may operate continuously in demanding industrial environments.

A suitable sensor installation can monitor shaft vibration and movement, helping maintenance personnel identify changes in mechanical condition.

Installation and System Integration

Correct installation is essential for measurement accuracy. The probe must be positioned properly, connected to compatible signal-conditioning equipment, and protected from unsuitable environmental conditions.

1. Verify the Measurement System

Before installation, confirm that the PR6424/105-030 is compatible with the selected extension cable and signal converter.

Check the complete part numbers, electrical characteristics, connector arrangement, cable length, and calibration requirements. Do not assume that all PR6424 probes can be connected to every converter without verification.

2. Select the Correct Target Surface

The PR6424 series uses a ferromagnetic steel target as its standard reference. The shaft material and surface condition should be checked before installation.

Differences in target material, surface treatment, or geometry can influence the sensor response. The target surface should be suitable for the specified measurement arrangement.

3. Position the Probe Correctly

The sensor must be installed at the recommended initial gap. The PR6424 series reference value for the nominal center air gap is approximately 2.7 mm.

The probe should be aligned with the intended measurement direction. Incorrect positioning can introduce measurement errors or cause the target to move outside the linear range.

4. Secure the Mechanical Mounting

Use the appropriate mounting arrangement for the exact probe configuration. Ensure that the sensor body is secured and cannot move during machine operation.

Excessive vibration or movement of the probe mounting can affect the measurement signal and make it difficult to distinguish actual shaft movement from sensor movement.

5. Route and Protect the Cable

The probe cable should be routed away from sources of electrical interference, excessive heat, mechanical abrasion, and sharp edges.

Maintain the cable’s specified minimum bending radius. Avoid excessive tension or repeated bending near the sensor connection and connector.

The cable configuration and maximum permissible temperature should be checked against the exact product variant.

6. Connect the Signal Converter

Connect the sensor to a compatible signal converter using the specified cable and connector arrangement.

The converter should be configured for the correct sensor type and measurement range. Confirm that the output signal is stable and corresponds to the expected probe gap before connecting it to the machinery monitoring system.

7. Calibrate and Verify the Measurement

After installation, check the initial gap and verify the sensor response using the applicable calibration procedure.

Confirm the output at the required measurement points and compare it with the expected response. Record the installation position, cable configuration, converter settings, and calibration results for future maintenance.

Compatible System Components

A PR6424 measurement arrangement normally includes several components working together. The probe itself provides the sensing function, while extension cables and signal converters complete the measurement chain.

The components listed above are examples of equipment used in a complete measurement system. They are not necessarily supplied with the PR6424/105-030 sensor.

Alternative Models and Replacement Considerations

The PR6424 family includes different probe configurations and ordering codes. Replacement selection should be based on the complete part number and the installed measurement system.

Before replacing the PR6424/105-030, compare:

• Sensor head diameter and mechanical dimensions.
• Thread type and mounting arrangement.
• Probe sensitivity and linearity.
• Static and dynamic measurement ranges.
• Nominal center air gap.
• Cable length and cable construction.
• Connector type and pin arrangement.
• Target material and shaft geometry.
• Operating temperature and environmental limits.
• Compatibility with the existing signal converter.
• Monitoring system input and configuration requirements.

A sensor with the same nominal diameter is not necessarily a direct replacement. Electrical compatibility and calibration characteristics must also match the installed measurement chain.

Key Advantages

Non-Contact Measurement

The sensor measures shaft displacement without touching the rotating surface. This avoids mechanical contact between the probe and the shaft during normal operation.

High Measurement Sensitivity

The PR6424 series has a published sensitivity of 4 V/mm. This allows small changes in the probe-to-target gap to be represented by measurable changes in output voltage.

Dynamic and Static Measurement

The sensor family supports both static displacement measurement and dynamic shaft movement measurement. This makes it suitable for different machinery monitoring requirements.

Compact 16 mm Sensing Head

The 16 mm sensor head provides a compact sensing format for suitable industrial machinery installations.

Industrial Rotating Equipment Applications

The PR6424 family is designed for monitoring applications involving turbines, compressors, pumps, fans, and other critical rotating machinery.

Integration with Machinery Monitoring Systems

When paired with compatible extension cables and signal converters, the sensor can provide displacement information for industrial monitoring and protection systems.

Support for Condition-Based Maintenance

Continuous or periodic shaft measurements can help maintenance teams identify changes in machinery behavior and plan inspections based on equipment condition.

Technical FAQs

1. What is the Epro PR6424/105-030?

The Epro PR6424/105-030 is a 16 mm non-contact eddy current sensor designed for measuring shaft displacement and vibration in rotating industrial machinery.

2. What is the measurement principle?

It uses the eddy current principle. An electromagnetic field is generated at the probe tip, and changes in the field caused by a nearby conductive target are used to determine the distance between the sensor and the target.

3. What is the sensor head diameter?

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

4. What is the sensitivity of the PR6424 series?

The published reference sensitivity is 4 V/mm, equivalent to approximately 101.6 mV/mil. The specified linearity is within ±1.5%.

5. What is the static measurement range?

The PR6424 series has a published static measurement range of ±2.0 mm. The actual installation must maintain the correct initial gap and target positioning.

6. Can the sensor measure shaft vibration?

Yes. It can detect dynamic changes in the distance between the probe and a rotating shaft. When connected to compatible monitoring equipment, the resulting signal can be used to evaluate shaft vibration.

7. What materials can be used as the measurement target?

The series specification uses ferromagnetic steel as its reference target material, with 42CrMo4 identified as the standard material. Other materials should be evaluated against the applicable calibration requirements.

8. Does the sensor work independently?

No. The probe is normally part of a measurement chain that includes compatible extension cabling and a signal converter or monitoring instrument. The exact components depend on the installed system.

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

Check the complete model number, probe diameter, mounting thread, cable length, connector, sensitivity, measurement range, temperature limits, and signal converter compatibility. These details determine whether the replacement will operate correctly.

10. What is the weight of the PR6424/105-030?

The supplied product weight is 0.2 kg. Emerson’s PR6424 series reference specification lists approximately 200 grams for the sensor with a 1-meter cable and without armor.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/105-030, verify the complete ordering code and compare it with the identification label on the existing sensor. The PR6424 family includes multiple probe configurations, and differences in cable length, mounting details, and electrical characteristics can affect replacement compatibility.

For critical machinery, the sensor should be sourced together with a clear understanding of the installed signal-conditioning system. Confirm the extension cable and converter requirements before ordering. A probe that physically fits the mounting location may still be unsuitable if its electrical characteristics do not match the existing measurement chain.

For used or surplus equipment, request photographs of the sensor body, identification label, cable, and connector. Inspect the sensing tip and threaded section for mechanical damage. Check cable insulation and connector condition, and request available test or calibration information where appropriate.

During routine maintenance, inspect the probe mounting, cable routing, connector security, and surrounding environment. Confirm that the sensor remains correctly positioned and that the measurement signal is stable. Avoid pulling the cable, bending it below its specified radius, or exposing it to temperatures outside the applicable product limits.

For replacement projects, record the original probe gap, converter settings, and monitoring-system configuration. After installation, perform the required calibration and signal verification before returning the monitored machinery to normal service.

Conclusion

The Epro PR6424/105-030 16 mm Eddy Current Sensor is designed for non-contact measurement of shaft displacement and vibration in critical rotating machinery. Its PR6424 family specifications include 4 V/mm sensitivity, ±2.0 mm static measurement range, 0–1,000 μm dynamic measurement range, and a nominal center air gap of approximately 2.7 mm.

The sensor can be used in suitable monitoring arrangements for turbines, compressors, pumps, fans, and other rotating equipment. For reliable performance, it must be installed with the correct target material, mounting position, extension cable, and compatible signal converter.

Accurate identification of the complete model number is essential when purchasing or replacing this sensor. Confirming its mechanical and electrical compatibility helps maintain measurement accuracy and supports reliable machinery condition monitoring.