Product Overview

The Epro PR6424/105-101 16 mm Eddy Current Sensor is a non-contact displacement sensor designed for monitoring the condition and operating behavior of rotating machinery. Manufactured under the EPRO product line associated with Emerson, the PR6424 series is used in machinery protection and condition-monitoring applications where accurate measurement of shaft movement is important.

The sensor operates using the eddy-current measurement principle. It detects changes in the distance between its sensing tip and a conductive metallic target without making physical contact with the rotating component. This makes it suitable for continuous monitoring of shaft vibration, displacement, position, and other dynamic mechanical conditions.

The PR6424 series is commonly applied to critical rotating equipment, including steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. In these machines, changes in shaft movement can provide useful information about mechanical condition, alignment, bearing behavior, and operating stability.

The PR6424/105-101 has a nominal sensor head diameter of 16 mm and a supplied product weight of approximately 0.2 kg. Its compact sensing head allows installation in appropriately designed monitoring locations around rotating machinery.

A complete eddy-current measurement system normally includes a sensor probe, extension cable where required, and a compatible signal converter or measuring unit. The probe itself detects the distance to the target, while the associated electronics convert the sensor response into a usable measurement signal.

When selecting this model for maintenance or replacement, engineers should verify the complete ordering code, cable arrangement, connector type, mounting dimensions, and compatibility with the installed monitoring electronics. Different PR6424 variants may have different mechanical and connection configurations.

Technical Specifications

Note: The performance values above are PR6424 family reference specifications. Confirm the exact electrical, mechanical, cable, connector, and temperature specifications for the PR6424/105-101 before installation.

Function and Working Principle

The PR6424/105-101 uses electromagnetic induction to measure the distance between its sensing tip and a metallic target. This measurement method is commonly called eddy-current sensing.

1. Non-Contact Measurement

The sensor generates an electromagnetic field around its sensing tip. When a conductive metallic target approaches the probe, the field induces eddy currents in the target surface.

These currents affect the electromagnetic response of the sensor. The associated measurement electronics detect the change and convert it into a signal representing the distance between the probe and the target.

Because the probe does not need to touch the rotating shaft, it can continuously measure shaft movement without introducing mechanical contact between the sensor and the monitored component.

2. Shaft Displacement Measurement

The PR6424 series is designed to measure shaft displacement within its specified measuring range. Depending on the installation and monitoring configuration, it can be used to detect radial or axial movement.

Radial displacement measurements are commonly used to monitor shaft movement relative to the bearing housing. Axial measurements help identify changes in the shaft’s position along its rotational axis.

These measurements can help operators identify abnormal mechanical conditions before they develop into more serious equipment problems.

3. Vibration Monitoring

Shaft vibration is an important indicator of rotating machinery condition. Excessive vibration may be associated with imbalance, misalignment, bearing deterioration, mechanical looseness, or other operating problems.

The PR6424 sensor measures dynamic changes in the gap between the probe and the shaft. When connected to compatible monitoring electronics, this information can be used to evaluate shaft vibration and identify changes in machine behavior.

4. Position and Eccentricity Monitoring

The sensor can also be used for static position and eccentricity measurements. These measurements help engineers understand the relationship between the shaft and its surrounding mechanical structure.

In turbine applications, position and eccentricity information can be useful during startup, shutdown, and normal operation. The measurement system must be configured correctly to distinguish static displacement from dynamic shaft movement.

5. Signal Conversion and Monitoring

The probe is one part of a complete measurement chain. Its electrical response must be processed by compatible signal-conditioning or monitoring electronics.

The converter provides the output required by the machinery monitoring system. Depending on the installed architecture, the resulting measurement can be displayed locally, transmitted to a control system, or used by machinery protection logic.

Correct matching between the sensor, cable, converter, and monitoring channel is essential for reliable measurement.

Role in Industrial Machinery Monitoring Systems

The PR6424/105-101 can serve as a sensing component in machinery protection and condition-monitoring installations. It provides measurement information that helps operators and maintenance engineers evaluate the mechanical behavior of rotating equipment.

Turbine Monitoring

Steam, gas, and hydro turbines operate with rotating shafts and high mechanical demands. Shaft displacement and vibration measurements are important for evaluating operating stability.

The sensor can be installed at suitable measurement locations to monitor shaft movement relative to the machine structure. The resulting signals can be processed by compatible machinery protection equipment.

Compressor Protection

Industrial compressors may operate continuously under changing load and process conditions. Abnormal shaft vibration or displacement can indicate developing mechanical problems.

A properly configured eddy-current measurement system can provide continuous shaft-motion information for compressor monitoring.

Bearing Condition Assessment

Shaft vibration and position measurements can contribute to bearing-condition assessment. Changes in shaft movement may be associated with bearing wear, clearance changes, lubrication problems, or mechanical misalignment.

The sensor does not independently diagnose every bearing fault. Its measurements should be evaluated together with other condition-monitoring data and maintenance findings.

Integration with Monitoring Equipment

The PR6424 sensor is intended to work with compatible signal converters and machinery monitoring systems. Before replacing an existing probe, engineers should confirm the required sensor characteristics and the compatibility of the connected monitoring channel.

A sensor with the same nominal diameter is not necessarily interchangeable if its electrical characteristics, cable configuration, or converter requirements differ.

Industrial Applications

The PR6424/105-101 is suitable for consideration in industrial installations that require non-contact shaft measurement. Its application depends on the machine geometry, target material, measurement range, and compatibility with the complete monitoring system.

1. Steam Turbines

Steam turbines contain high-speed rotating assemblies that require continuous monitoring. Shaft displacement and vibration measurements can help identify abnormal movement during startup and normal operation.

The PR6424 series is designed for critical turbomachinery applications, making it relevant to suitable turbine monitoring installations.

2. Gas Turbines

Gas turbines operate under demanding thermal and mechanical conditions. Shaft position and vibration monitoring can provide important information about rotor behavior and machine stability.

The exact sensor temperature rating and installation arrangement must be checked for the selected probe variant and measurement location.

3. Hydro Turbines

Hydro turbines are used in power-generation facilities and may operate under varying load conditions. Shaft movement monitoring helps maintenance teams evaluate rotating equipment behavior and identify changes that require inspection.

4. Industrial Compressors

Large compressors often operate continuously in process plants, refineries, and other industrial facilities. Non-contact displacement sensors can monitor shaft movement without direct mechanical contact.

The measurement data can support preventive maintenance and machinery protection strategies.

5. Pumps and Fans

Industrial pumps and fans may also require shaft vibration and position monitoring, particularly in installations where equipment reliability is important to production continuity.

The sensor can be used where the shaft diameter, target material, mounting arrangement, and measurement requirements fall within the applicable PR6424 specifications.

6. Power Generation Equipment

Power-generation facilities depend on reliable operation of turbines, generators, and associated rotating equipment. Eddy-current probes can form part of a wider machinery monitoring system used to track shaft movement and operating condition.

Installation and System Integration

Correct installation is essential for obtaining reliable measurements from the PR6424/105-101. Probe positioning, target material, air gap, cable routing, and electronic compatibility all influence measurement performance.

1. Verify the Complete Model Number

Before installation, confirm that the probe is the required PR6424/105-101 variant. Check the identification label, cable assembly, connector arrangement, and mechanical configuration.

Do not assume that every PR6424 probe can replace another variant solely because both have a 16 mm sensing head.

2. Check the Target Material

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

Target material affects sensor response. If the shaft material differs from the reference material, the measurement system may require appropriate calibration or engineering verification.

3. Maintain the Correct Air Gap

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

Incorrect probe positioning can reduce measurement accuracy or cause the sensor to operate outside its intended linear range.

4. Observe Mechanical Clearance

The sensing tip and surrounding installation area must maintain the required clearance from nearby metallic components. Unintended metal near the probe can influence its electromagnetic field and affect the measurement.

Use the manufacturer’s mechanical drawings when designing mounting brackets, probe holders, and installation openings.

5. Route the Sensor Cable Correctly

The sensor cable should be routed in accordance with the manufacturer’s instructions. Avoid sharp bends, excessive tension, crushing, and unnecessary proximity to high-power electrical conductors.

The exact cable length, shielding, connector, and armored or non-armored construction must be confirmed for the /105-101 variant.

6. Connect Compatible Monitoring Electronics

The probe must be connected to the appropriate signal converter or monitoring input. Confirm electrical compatibility, cable requirements, and channel configuration before energizing the measurement system.

A mismatch between the sensor and converter can result in incorrect readings or unreliable monitoring.

7. Calibrate and Verify the Measurement

After installation, verify the initial gap and check the sensor output across the expected measurement range. Confirm that the monitoring system displays plausible shaft-position and vibration values.

Record the installation position, calibration information, and baseline operating measurements for future maintenance comparisons.

Compatible System Components

The PR6424/105-101 normally operates as part of a complete machinery measurement system. The following components may be used depending on the monitoring architecture.

These are examples of components used in a complete measurement installation. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 family contains different probe variants. Although they may share the same nominal 16 mm sensor head diameter, their cable lengths, connectors, mounting arrangements, and environmental specifications can differ.

Before selecting a replacement, check:

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

A replacement should be approved only after confirming that its electrical and mechanical characteristics match the original installation.

Key Advantages

Non-Contact Measurement

The eddy-current principle allows the sensor to measure shaft movement without physical contact. This supports continuous monitoring of rotating equipment without introducing mechanical wear at the sensing interface.

Suitable for Critical Rotating Machinery

The PR6424 series is designed for machinery such as turbines, compressors, pumps, and fans where shaft movement monitoring can contribute to equipment protection and maintenance planning.

Displacement and Vibration Monitoring

The sensor can provide information about static shaft position and dynamic movement when connected to compatible measurement electronics.

Compact 16 mm Sensing Head

The 16 mm sensor head provides a defined installation size for suitable machinery monitoring arrangements.

Stable Measurement Characteristics

PR6424 series documentation specifies sensitivity of 4 V/mm, linearity of up to ±1.5%, and long-term drift below 0.3%. These characteristics support consistent measurement when the sensor is installed and calibrated correctly.

Industrial Construction

The series uses a stainless-steel sensor sleeve and PTFE cable material. The actual environmental suitability must be checked against the exact probe configuration.

Integration into Machinery Protection Systems

The sensor can form part of a broader condition-monitoring arrangement, providing displacement information to compatible converters and machinery monitoring equipment.

Technical FAQs

1. What is the Epro PR6424/105-101?

The PR6424/105-101 is a 16 mm eddy-current sensor designed for non-contact measurement of shaft displacement and vibration in rotating machinery.

2. What is the sensor head diameter?

The nominal sensor head diameter is 16 mm.

3. What measurement principle does it use?

It uses electromagnetic induction, commonly known as the eddy-current principle. Changes in the distance between the probe and a metallic target affect the sensor response.

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

The published PR6424 family specification gives a typical sensitivity of 4 V/mm, equivalent to approximately 101.6 mV/mil.

5. What is its static measuring range?

The PR6424 series specification lists a static measuring range of ±2.0 mm. The usable range in an installed system depends on the probe, converter, calibration, and target conditions.

6. Can it measure shaft vibration?

Yes. When connected to compatible monitoring electronics, it can measure dynamic shaft movement and provide information used for vibration monitoring.

7. Which materials can it measure?

The series is specified for ferromagnetic steel targets, with 42CrMo4 steel used as the standard reference material. Other target materials should be evaluated before installation.

8. Where is the PR6424 sensor commonly used?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, fans, generators, and other rotating machinery.

9. Can the PR6424/105-101 replace another PR6424 model?

Not automatically. The complete model number, cable configuration, connector, mounting dimensions, temperature limits, and converter compatibility must be checked before replacement.

10. What should be checked before purchasing this sensor?

Confirm the exact model number, sensor head diameter, cable and connector configuration, physical condition, weight, and compatibility with the installed monitoring system. For critical machinery, verify the sensor’s measurement characteristics against the original equipment requirements.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/105-101, begin by confirming the complete part number and comparing it with the probe installed on the machine. The PR6424 family includes multiple variants, and small differences in the suffix can represent important changes in cable length, connector type, or mechanical configuration.

For replacement projects, check the sensor head diameter, mounting thread, cable construction, connector arrangement, and compatible converter. Do not select a probe solely because it belongs to the same product family.

For used or surplus units, request clear photographs of the sensor head, threaded section, cable, connector, and identification label. Inspect the cable for cuts, crushing, damaged insulation, or signs of excessive bending. Confirm whether the supplied weight of 0.2 kg refers to the sensor alone or to the sensor with its cable.

During maintenance, inspect the probe mounting, cable routing, connector condition, and sensor clearance. Compare current measurements with established baseline readings and investigate significant changes in shaft displacement or vibration.

For critical rotating machinery, sensor replacement should be followed by appropriate calibration and functional verification. Record the replacement model, installation gap, monitoring-channel configuration, and commissioning results.

Conclusion

The Epro PR6424/105-101 16 mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in industrial rotating machinery. As part of the PR6424 sensor family, it is intended for applications involving turbines, compressors, pumps, fans, and other critical rotating equipment.

Its 16 mm sensing head and eddy-current measurement principle make it suitable for installations that require continuous monitoring without physical contact with the shaft. The PR6424 family offers 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.

For reliable operation and replacement, engineers should verify the complete /105-101 configuration, including cable, connector, mounting, temperature requirements, and compatibility with the associated signal converter and machinery monitoring system.